Calibration method for multi-channel transmitter calibration device

Abstract

The application discloses a kind of calibration methods of multichannel transmitter calibration device, belong to metrological calibration technical field.The method includes: in response to configuration instruction, the connection state of control power module and target channel, make target channel enter working state;Original electric signal in power supply loop is collected, original electric signal includes loop current value and power supply voltage value;Original electric signal is modified using preset calibration parameter, and target measurement value is output.The application has adopted the undisturbed switching control based on compliance margin prediction, and the double-variable coupling error compensation model based on power supply voltage and loop current.The method solves the non-linear measurement error problem caused by voltage fluctuation under the multi-channel common power supply architecture, and the protection misjudgment problem caused by hard switching transient, realizes the automatic calibration without external precision power supply intervention.

Description

Technical Field

[0001] This invention belongs to the field of metrology and calibration technology, and in particular, it relates to a calibration method for a multi-channel transmitter calibration device. Background Technology

[0002] In the field of industrial process control, (4-20) mA analog transmitters are widely used for transmitting key parameters such as temperature and pressure. Their measurement accuracy is directly related to production safety and quality, and they need to be regularly calibrated with high precision. With the expansion of industrial systems, the demand for multi-channel parallel calibration equipment that can simultaneously power and measure multiple transmitters is increasing, requiring calibration devices to have a high degree of integration and automation.

[0003] Currently, most common calibration equipment adopts an architecture where the power supply module and measurement module are separate, or uses a mechanical switch to manually switch between 12V / 24V power supply levels and two-wire / three-wire wiring modes. In terms of data processing, existing technologies generally employ a single-variable linear calibration model, assuming a constant power supply voltage and only performing simple linear corrections to the measured display value based on the input standard current, such as adjusting a potentiometer or using gain / zero-point coefficient corrections. Furthermore, they often employ hard protection logic based on fixed thresholds to handle overcurrent or short-circuit conditions.

[0004] However, in multi-channel integrated designs where power supply and measurement share the same circuit, there are problems such as difficulty in eliminating coupling errors and poor transient stability during switching. Therefore, further research and innovation are needed to solve the aforementioned problems in existing technologies. Summary of the Invention

[0005] Purpose of the invention: In view of the above-mentioned problems in the prior art, this application provides a calibration method for a multi-channel transmitter calibration device.

[0006] Technical solution: According to one aspect of this application, a calibration method for a multi-channel transmitter calibration device includes:

[0007] In response to the configuration command for the target channel, the connection status between the power module and the target channel is controlled to put the target channel into working state and obtain the power supply circuit for the target channel;

[0008] In operation, the raw electrical signals in the power supply circuit are collected;

[0009] Based on the original electrical signal, the original electrical signal is corrected using calibration parameters, and the target measurement value of the target channel is output.

[0010] Beneficial Effects: This invention employs a non-disruptive switching control based on compliance margin prediction and a bivariate coupled error compensation model based on supply voltage and loop current. This method solves the problem of nonlinear measurement errors caused by voltage fluctuations in multi-channel shared power supply architectures, as well as protection misjudgments caused by hard switching transients, achieving automated calibration without the need for an external precision power supply. The related technical effects will be described in detail below with reference to specific embodiments. Attached Figure Description

[0011] Figure 1 A flowchart illustrating a calibration method for a multi-channel transmitter calibration device provided in this application embodiment.

[0012] Figure 2 A flowchart illustrating the connection status between the control power module and the target channel provided in an embodiment of this application.

[0013] Figure 3 This is a flowchart illustrating the correction process of the original electrical signal using calibration parameters, provided as an embodiment of this application.

[0014] Figure 4 A flowchart of the self-disturbance calibration process provided in the embodiments of this application.

[0015] Figure 5 A flowchart illustrating the anomaly protection provided in this application embodiment. Detailed Implementation

[0016] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0017] It should be noted that the terms "first," "second," etc., in the specification and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0018] To address the aforementioned issues, the applicant conducted in-depth searches and analyses, and discovered:

[0019] Specifically, the single-variable calibration method ignores the fact that in a shared power supply loop, voltage fluctuations caused by load changes or line impedance can be directly coupled to current measurements, resulting in nonlinear system errors that cannot be eliminated by conventional methods.

[0020] Meanwhile, hard switching control based on fixed delay lacks awareness of loop compliance voltage and residual energy, which can easily generate uncontrollable surges or voltage drops at the moment of channel switching, causing the protection mechanism to be falsely triggered or the device under test to power off and restart, affecting the accuracy and continuity of multi-channel parallel calibration.

[0021] To solve these problems, combined with Figures 1 to 5 The present invention will be specifically described through the following embodiments.

[0022] In some embodiments, an exemplary scheme for a calibration method of a multi-channel transmitter calibration device is provided, and the hardware foundation of the multi-channel transmitter calibration device is also described, providing a hardware carrier and methodological framework for subsequent advanced control and calibration algorithms.

[0023] In each embodiment, the target channel refers to the specific measurement channel currently undergoing calibration, while other channels refer to all measurement channels in the device other than the target channel. When it is necessary to distinguish multiple channels, they can be designated using numbering methods such as Channel 1, Channel 2, etc. The same applies to similar components such as switches, terminals, and ammeters, which are distinguished by serial numbers (e.g., Switch 3, Switch 4, Terminal 2, Ammeter 1, etc.). The serial numbers are only used to identify specific components and have no other special meaning.

[0024] In this embodiment, the multi-channel transmitter calibration device adopts an integrated design where power supply and measurement share the same circuit. The device's hardware architecture mainly includes a microcontroller unit (MCU), a multi-voltage power supply module, a measurement switching module, a signal acquisition module, and a human-machine interface.

[0025] The microcontroller unit (MCU) acts as the controller, responsible for parsing configuration commands and coordinating the timing actions of each module. The multi-voltage power supply module features three independent regulated outputs: a 5V power supply for the MCU and display, and switchable 12V and 24V power supplies for the measurement channels. The measurement switching module includes a relay matrix for switching between power supply voltage levels and between two-wire and three-wire wiring modes. The signal acquisition module includes a high-precision analog-to-digital converter (ADC) for real-time acquisition of current and voltage signals from the measurement circuit.

[0026] In the software architecture of this embodiment, the microcontroller unit (MCU) establishes an independent state record structure for each measurement channel i. This structure includes the following fields: the current and target wiring modes, the current and target power supply voltage levels, the acquired current time series and voltage time series, the calculated current change rate and voltage change rate, the compliance margin calculated based on load prediction, and the current state machine state.

[0027] The State field can take the following values: OFF (off), PRE_RAMP (pre-charge observation), RAMP (soft-start ramp-up), STABLE (steady state), SWITCHING (switching), and FAULT (fault). Alternatively, the State field can take the following values: OFF (off, corresponding to the off state), PRE_RAMP (pre-charge observation), RAMP (soft-start ramp-up), STABLE (steady state), SWITCHING (switching, an extended state representing the system's power supply level / wiring mode switching process), and FAULT (fault), suitable for scenarios involving channel switching. By maintaining a standardized data structure, all subsequent control algorithms can access the context information of any channel through a unified interface.

[0028] Step 101: In response to the configuration command for the target channel, control the connection status between the power module and the target channel to put the target channel into working state and obtain the power supply circuit for the target channel.

[0029] In this embodiment, the configuration command refers to a control data packet containing parameters such as channel number, target voltage level, and wiring mode. This command can originate from a physical switch operation by the user on the device panel, or from a digital command sent by the host computer software via serial port. Upon receiving the configuration command, the microcontroller unit (MCU) parses the target channel ID, for example, channel 1.

[0030] Furthermore, the MCU sends a control signal to the measurement switching module, driving the corresponding relay to connect the specified power output, such as 24V, to the power supply terminal of channel 1, establishing a closed electrical circuit. At this point, the target channel enters the working state, the transmitter starts to be powered on and outputs a signal, forming the power supply circuit for the target channel.

[0031] Step 102: In the working state, collect the original electrical signals in the power supply circuit.

[0032] In this embodiment, the original electrical signal refers to an analog or digital quantity directly obtained from the hardware circuit without any algorithmic correction. Specifically, the ADC in the signal acquisition module samples the current flowing through the power supply circuit to obtain the original current value. Simultaneously, the ADC also samples the terminal voltage across the power supply circuit to obtain the original voltage value. The acquisition process can be a single trigger or continuous sampling at a preset frequency. To eliminate high-frequency noise interference, the MCU can also perform a moving average filtering process on multiple continuously sampled data points to obtain stable original electrical signal data.

[0033] Step 103: Based on the original electrical signal, the original electrical signal is corrected using calibration parameters, and the target measurement value of the target channel is output.

[0034] In this embodiment, due to non-ideal factors such as component tolerances, line impedance, and power supply fluctuations in the hardware circuit, the directly acquired raw electrical signal often contains errors. Therefore, it must be corrected. The calibration parameters are correction coefficients pre-stored in the MCU's non-volatile memory, such as EEPROM (Electrically Erasable Programmable Read-Only Memory). The specific process of correction is that the MCU substitutes the acquired raw electrical signal into a preset algorithm model, uses the calibration parameters to perform calculations, and compensates for system errors. The final result obtained is the target measurement value, which will be sent to the display screen for display or uploaded to the host computer for recording. Based on this, the device can output high-precision measurement results, meeting the requirements of metrological calibration.

[0035] In the above, when the configuration command received by the MCU is in the wrong format or the channel number is out of the valid range, the system will refuse to execute it and will send an error code to the display screen or the host computer to prompt the user to re-enter the correct configuration command.

[0036] In other embodiments, alternative implementations based on physical switch detection and linear calibration are described. In particular, a low-cost implementation based on physical switch control and traditional linear calibration is described. This approach is suitable for basic devices that are cost-sensitive and do not require a high degree of automation, further supplementing the hardware protection circuitry and specific relay topology logic.

[0037] In the hardware circuit of this embodiment, each measurement channel's power supply circuit is connected in series with dual protection components to prevent damage to the device from short circuits and overloads. The first layer of protection can be a glass tube fuse, which is used to quickly melt and disconnect the circuit in the event of a severe short circuit. This protection is non-resettable and needs to be replaced after melting. The second layer of protection can be a PTC positive temperature coefficient thermistor, also known as a resettable fuse.

[0038] When the circuit current exceeds the rated value, such as 50mA, the PTC thermistor heats up and its resistance increases sharply, limiting the current. When the fault is cleared and the component cools down, the resistance returns to normal, and the circuit automatically resumes conduction. In other words, the dual protection mechanism improves the safety and durability of the device.

[0039] In some scenarios, the rated current of the PTC thermistor is selected as 50mA. This value is determined based on twice the safety margin of the transmitter's standard 4-20mA operating range, so that it does not trigger protection during normal operation and can respond quickly in the event of a short circuit fault.

[0040] Step 201: Detect the physical state of the voltage selection switch and the mode selection switch to determine the power supply level and wiring mode of the target channel.

[0041] In this embodiment, a toggle switch is provided on the device panel for each channel. The voltage selection switch is used to switch between 12V and 24V, and the mode selection switch is used to switch between two-wire and three-wire systems. The MCU reads the position of the physical switches in real time by scanning the level states of the GPIO (General Purpose Input / Output) ports. For example, when the GPIO... _1 When the GPIO reads a high level, the power supply level is determined to be 24V; when the GPIO reads a high level... _2 When the reading is low, the wiring mode is determined to be two-wire.

[0042] Or, to put it another way, the GPIO port includes the first detection port (GPIO). _1 ) and second detection port (GPIO) _2 ), including GPIO _1 Electrically connected to the voltage selection switch, GPIO _2 Electrically connected to the mode selection switch.

[0043] It should be understood that physical testing methods are intuitive, reliable, and in line with traditional operating habits.

[0044] Step 202: Switch the circuit topology of the measurement loop according to the wiring mode, and configure the power module according to the power supply level.

[0045] In this embodiment, the MCU drives the relay matrix according to the determined parameters. For the power supply level, if 12V is selected, the power selection relay closes to the 12V regulated power supply output. For the wiring mode, if a two-wire system is selected, the mode switching relay closes, internally shorting the positive power supply terminal and the positive measurement terminal of the measurement circuit, sharing the positive and negative cables; if a three-wire system is selected, the mode switching relay opens, allowing the positive power supply terminal to output independently and the positive measurement terminal to input independently, with both sharing the negative terminal.

[0046] The topology switching logic described above enables the device to be compatible with different types of transmitter interfaces.

[0047] Step 203: After completing the circuit topology switch, wait for a preset delay time and then control the power module to supply power to the target channel.

[0048] Accordingly, considering the mechanical vibration of the relay contacts during operation and the potential unstable inrush current in the transmitter during initial power-on, direct measurement would cause reading jumps. Therefore, a fixed delay timer is included in the program. When the relay operation command is issued, the MCU starts the timer and waits for a preset delay duration, which can be set to 500ms. During the delay, data acquisition or display refresh is disabled. Once the delay ends, the circuit is considered stable, and the MCU turns on the power switch for the measurement channel, officially supplying power to the target channel.

[0049] The original electrical signal is corrected using calibration parameters, specifically including:

[0050] Step 204: Invoke the pre-stored gain coefficient and zero coefficient for the target channel.

[0051] In this embodiment, the calibration parameters can be linear model parameters. For each channel, the gain coefficient K and zero-point coefficient B are pre-calibrated at the factory or during periodic maintenance. For example, the gain coefficient K can be expressed as the ratio of the standard current difference to the measured current difference, and the zero-point coefficient B represents the zero-point offset. These coefficients are stored in a lookup table, and the MCU retrieves them based on the current channel number.

[0052] Step 205: Using the gain coefficient and zero-point coefficient, perform a linear transformation calculation on the original electrical signal to obtain the target measurement value.

[0053] In this embodiment, the MCU reads the original current value I. _raw Then, the target measurement value I is calculated using a linear formula. _target The specific calculation formula is: I _target =K×I _raw +B. For example, if the current channel's gain coefficient K is 1.002 and the zero-point coefficient B is 0.005mA, the acquired raw current I... _raw If the current is 10.000mA, then the calculated target measurement value I is... _target It is 10.025mA.

[0054] It should be understood that linear calibration methods involve less computation, are easy to implement, and can meet the calibration requirements of general industrial precision.

[0055] In other words, the formula for calculating the target measurement value can be described as:

[0056] I _target =K×I _raw +B;

[0057] Among them, I _target The corrected target measurement value (unit: mA); K is the pre-stored gain coefficient (dimensionless); I _raw B represents the acquired raw current value (unit: mA); B represents the pre-stored zero-point coefficient (unit: mA).

[0058] In other embodiments, an optional implementation of disruptive handover timing control and compliance prediction is provided. This method addresses surge impacts and insufficient power supply during multi-channel handover, making it suitable for calibration scenarios with high stability requirements. This embodiment introduces a compliance voltage estimation formula and a soft-start control strategy to achieve intelligent power management.

[0059] In this embodiment, seamless switching requires two things: first, confirming that the old channel is disconnected and has no residual energy before connecting the new channel; and second, smoothly powering on the new channel according to load demand. To achieve the former, the system introduces a real-time monitoring mechanism for the rate of current change; to achieve the latter, the system introduces the concept of compliance margin, which is the margin between power supply capacity and load demand.

[0060] Accordingly, before controlling the connection status between the power module and the target channel, an event-driven disconnection confirmation is also included, specifically:

[0061] Step 301: Monitor the residual loop current and its rate of change in the previous working channel in real time.

[0062] In this embodiment, before switching to the next target channel, the MCU monitors the currently operating channel or the channel that has just been disconnected at a high sampling rate. The MCU acquires the residual loop current in the loop in real time, calculates the difference between adjacent sampling points, and obtains the current change rate dI / dt. For example, if the sampling interval is 1ms, the current at the current moment is 0.12mA, and the current at the previous moment was 0.15mA, then the current change rate is -0.03mA / ms.

[0063] In other words, the formula for calculating the rate of change of current (discrete differential) can be expressed as:

[0064] dI / dt=(I _t -I _t-1 ) / Δt;

[0065] Where dI / dt is the rate of change of current at the current moment (unit: mA / ms); I _t I represents the loop current value collected at the current sampling time t. _t-1 Δt represents the loop current value collected at the previous sampling time t-1; Δt is the time interval between the two samplings (unit: ms).

[0066] Step 302: Determine whether the residual circuit current is less than the preset turn-off current threshold and whether the absolute value of the current change rate is less than the preset stability threshold.

[0067] Specifically, the system has preset disconnection criteria. The shutdown current threshold can be set to 0.1mA to determine whether the circuit has been disconnected. The stability threshold can be set to 0.05mA / ms to determine whether the capacitor discharge process in the circuit has ended and whether the state is stable. Only when the residual loop current is less than 0.1mA and |dI / dt| is less than 0.05mA / ms will the MCU determine that the previous channel has been safely disconnected and the switching conditions are met.

[0068] In other words, event-driven criteria are more efficient and safer than fixed delays.

[0069] The turn-off current threshold can be set to 0.1mA, with a value ranging from 0.05mA to 0.2mA. The stabilization threshold can be set to 0.05mA / ms, with an adjustable range of 0.02mA / ms to 0.1mA / ms, determined according to the circuit time constant.

[0070] Step 303: Execute connection control for the target channel only if the above conditions are met simultaneously; otherwise, maintain a waiting state.

[0071] In this embodiment, if both conditions are not met simultaneously, it indicates that there is still residual energy in the circuit or that transient oscillations are occurring. Forcing a switch in this situation could generate electrical sparks or impact the newly connected transmitter. Therefore, the MCU will maintain its current state and continue monitoring in a loop until the conditions are met or a timeout alarm is triggered. Only when the conditions are met will the MCU issue a command to close the relay of the target channel and begin establishing a new connection.

[0072] According to one aspect of this application, after the connection control is executed and before the output voltage ramps up, a pre-charge observation state is entered to confirm that there are no abnormal spikes in the circuit. In this embodiment, after the MCU controls the relay to close and completes the circuit topology switching, the power output is not started immediately, but a pre-charge observation window with a duration of 20ms is entered.

[0073] During this period, the MCU acquires the loop voltage at a high frequency. If an abnormal spike exceeding 0.5V is detected in the loop voltage, it indicates a possible inductive charge release or incorrect wiring in the external loop. In this case, the MCU will suspend the startup process and issue an alarm. Only if the voltage remains quiescent within the observation window will the system determine that the physical connection is safe and allow entry into the subsequent soft-start phase.

[0074] Controlling the connection status between the power module and the target channel, specifically including:

[0075] Step 304: Determine the target supply voltage for the target channel and obtain the loop compliance voltage required to maintain the current load of the target channel.

[0076] In this embodiment, the target supply voltage V _target This is the user-defined voltage level, such as 24V, also known as the target voltage. Circuit compliance voltage V _req This refers to the minimum terminal voltage required to maintain normal operation of the current load. The MCU can adjust this voltage based on the current set current I. _target For example, 20mA and the estimated total circuit resistance R. _loop To calculate V _req The specific estimation formula can be expressed as:

[0077] V _req =I _target ×R _loop +V _drop_min Among them, V _drop_min This is the minimum voltage drop required for the transmitter to operate normally, for example, 12V. R _loop Including line resistance and sampling resistance, which can be estimated using historical data.

[0078] Alternatively, the formula for the loop compliance voltage (static estimation) is:

[0079] V _req =I _target ×R _loop +V _drop_min ;

[0080] Among them, V _req Minimum loop compliance voltage (in V) required to maintain the target current; I _target Set the target current value (unit: mA); R _loop The estimated total loop resistance, including line resistance and sampling resistance (unit: Ω); V _drop_min The minimum pressure drop (in V) required for the transmitter to operate normally.

[0081] Step 305: Calculate the difference between the target supply voltage and the circuit compliance voltage to obtain the compliance margin.

[0082] In this embodiment, the MCU subtracts the loop compliance voltage from the target supply voltage to obtain the compliance margin. The formula is:

[0083] Margin=V _target -V _req For example, if V _target The calculated V is 24V. _req If the voltage is 22V, then the margin is 2V. This indicator reflects the current power supply capacity relative to the load demand.

[0084] In other words, the formula for calculating compliance margin can be expressed as:

[0085] Margin=V _target -V _req ;

[0086] Wherein, Margin represents compliance margin (unit: V); V _target The currently selected power supply voltage level, for example, 24V; V _req This is the compliant voltage for the circuit.

[0087] Step 306: Determine the soft-start ramp parameters based on the compliance margin, and control the output voltage of the power module to gradually increase according to the soft-start ramp parameters until the target supply voltage is reached.

[0088] In this embodiment, the MCU adaptively selects a soft-start strategy based on the margin. If the margin is greater than 2V, it indicates sufficient margin, allowing for a faster start-up speed, and the soft-start ramp parameter r is set to 1V / ms. If the margin is less than 1V, it indicates limited margin, and to prevent overshoot triggering overcurrent protection or causing voltage drop at power-on, a slower ramp parameter r is set to 0.2V / ms. Furthermore, the MCU uses PWM (Pulse Width Modulation) modulation or a digitally controlled power supply chip to control the output voltage to linearly rise from 0V to VV at a set slope r. _target .

[0089] The soft-start ramp parameter can be set to 0.5V / ms, with a range of 0.1V / ms to 2V / ms. The specific value is adaptively determined based on the compliance margin. For example, a fast ramp of 1V / ms to 2V / ms can be used when the compliance margin is greater than 3V, while a slow ramp of 0.1V / ms to 0.3V / ms should be used when the compliance margin is less than 1.5V.

[0090] It should also be understood that adaptive soft start avoids the surge caused by hard switching, achieving disturbance-free power-on.

[0091] According to another aspect of this application, before performing any switching action, the MCU performs full-dimensional feature extraction on the current channel state. While maintaining the current state without switching, the MCU acquires the current and voltage time series within a time window W (e.g., 100ms).

[0092] Furthermore, the MCU calculates the statistical feature vector F within this window. _i ={I _peak I _rms dI / dt _max V _min dV / dt _max}; Above, F _i Let I be the statistical characteristic vector of current and voltage within the i-th time window. _peak For the peak current within the corresponding time window, I _rms This represents the effective value of the current within the time window, dI / dt. _max V represents the maximum rate of change of current within this time window. _min It is the minimum voltage value within that time window, dV / dt _max This represents the maximum rate of change of voltage within that time window.

[0093] These features are not only used for subsequent disconnection criteria, but also serve as historical baseline data storage to assist in subsequent compliance predictions.

[0094] This embodiment provides an observation method that does not rely on preset structural parameters (such as line resistance) when determining the compliance voltage of the loop. Specifically, the MCU performs two-point sampling near the current operating point using a small voltage perturbation. For example, at the current output voltage V... _1 The measured current I _1 Fine-tune the output to V _2 Measured current I _2 By constructing an equivalent volt-ampere characteristic model of the circuit using two data points, and extrapolating it to the target current, the minimum terminal voltage required to maintain that target current is estimated. This method can dynamically adapt to the effects of line aging or changes in contact resistance.

[0095] Alternatively, the formula for the loop compliance voltage (two-point observation extrapolation) can be described as:

[0096] V _req =V _1 +(V _2 -V _1 )×(I _target -I _1 ) / (I _2 -I _1 );

[0097] Among them, V _req The loop compliance voltage is calculated based on observations; V _1 This is the output voltage during the first fine-tuning; V _2 This refers to the output voltage during the second fine-tuning; I _1 For voltage V _1 The measured loop current; I _2 For voltage V _2 The measured loop current; I _target The target current setting value can also be called the target current.

[0098] An example illustrates the specific implementation process of a collaborative protection and adaptive feedback mechanism based on a timing state context. This method introduces the concept of a state machine, which can identify the current timing stage of the device, dynamically adjust the fault discrimination logic, form a closed-loop feedback after a fault occurs, and automatically optimize subsequent control strategies. It can be used to solve the problems of transient startup states being easily misjudged as faults when multiple channels are operating in parallel, and the inability to self-heal when a single fault repeatedly triggers protection.

[0099] In this embodiment, the microcontroller unit (MCU) internally runs a finite state machine to maintain the logical state of each measurement channel in real time. To accurately describe this state, the system defines an enumeration type `State`, which specifically includes:

[0100] The IDLE state indicates that the channel is closed;

[0101] The precharge status PRE_RAMP indicates that the circuit is connected but the voltage has not yet been established;

[0102] The ramp-up status RAMP indicates that the voltage is rising during the soft start process;

[0103] The steady-state measurement status (STABLE) indicates that the voltage has stabilized and the measurement phase has begun.

[0104] Fault status: FAULT.

[0105] The MCU transitions between the aforementioned states based on configuration instructions and real-time voltage and current feedback.

[0106] In other words, the enumeration type State pre-enumerates all legal working states of the state machine, limiting the range of State values ​​to only preset state constants. This is applicable to basic measurement scenarios without active switching actions. To simplify the state machine logic, the enumeration type State defined by the system specifically includes: Idle state IDLE (corresponding to the shutdown state, representing the channel being closed), Precharge state PRE_RAMP (representing the circuit being connected but the voltage not yet established), Ramp state RAMP (representing the voltage rising during soft start), Steady-state measurement state STABLE (representing the voltage stabilizing and entering the measurement phase), and Fault state FAULT.

[0107] The MCU transitions between the above states in an orderly manner based on configuration instructions and real-time voltage and current feedback. If the switching function needs to be expanded, a SWITCHING state can be added to the enumeration type State.

[0108] Furthermore, anomaly protection can be implemented in the following ways:

[0109] Step 401: Monitor the current timing status of the target channel in real time. The timing status includes the ramp-up state where the power supply voltage is rising and the steady-state measurement state where the power supply voltage has stabilized.

[0110] Accordingly, the MCU periodically reads the current value of the state machine to determine the timing state. Specifically, when the MCU executes the soft-start program, it marks the state as the ramp-up state (RAMP); when the output voltage reaches the target value and the volatility converges, the state is updated to the steady-state measurement state (STABLE). For example, the system can set a decision time window; if the voltage remains within ±0.5V of the target value within 100ms, it is confirmed to have entered the steady-state measurement state.

[0111] After the soft start, the system enters the steady-state determination phase. The MCU calculates the rate of change of the loop current and the rate of change of the supply voltage in real time. The system presets steady-state determination thresholds, such as the current change rate threshold α. _stable The voltage change rate threshold β is 0.002 mA / ms. _stable The value is 0.01 V / ms. This only applies if the condition |dI / dt| is less than α. _stable And |dV / dt| is less than β _stable The MCU will only update the channel state to STABLE if this condition is met continuously for more than a stable time window (e.g., 500ms).

[0112] In other words, the rigorous determination based on bivariate derivatives avoids false steady-state misjudgments caused by power supply ripple or minor load drift.

[0113] On the other hand, the steady-state determination logic formula can also be expressed as:

[0114] Is _stable =(|dI / dt|<α _stable AND(|dV / dt|<β) _stable );

[0115] Among them, Is _stable This is a Boolean value indicating whether steady state has been reached; |dI / dt| is the absolute value of the rate of change of current; α _stable β is the preset current rate of change stability threshold; |dV / dt| is the absolute value of the voltage rate of change; _stable This is the preset voltage change rate stability threshold; AND represents a logical AND operation.

[0116] Step 402: When an abnormal fluctuation in the current in the power supply circuit is detected, a coordinated protection determination is performed according to the current timing status.

[0117] In this embodiment, abnormal fluctuations refer to events where the current amplitude exceeds the normal operating range. The MCU collects the loop current in real time. When the loop current is detected to be greater than a preset safety limit (e.g., 25mA), the system does not immediately disconnect the circuit, but instead enters the logic branch for collaborative protection determination. This branch selects different processing strategies based on the current state variables through a switch-case logic structure. Here, switch-case is the branch selection logic.

[0118] Step 403: If the system is in a ramping state, determine whether the abnormal fluctuations meet the characteristics of a startup transient. If so, maintain the current connection state; otherwise, trigger disconnection protection.

[0119] Alternatively, if the system is in a ramp-up state, it determines whether abnormal fluctuations meet the preset startup transient characteristics. If so, it maintains the current connection state; otherwise, it triggers disconnection protection.

[0120] In this embodiment, the startup transient characteristic typically manifests as a short-duration spike pulse, a physical phenomenon caused by the charging of the transmitter's internal capacitor or the back electromotive force of the inductor. The preset startup transient characteristic can be defined by its peak amplitude and duration. For example, if the peak current is less than 40mA and the duration is less than 10ms, it is determined to meet the startup transient characteristic.

[0121] In other words, 40mA is the peak threshold for the start-up transient, adjustable from 30mA to 50mA, and should be greater than 1.5 times the transmitter's maximum operating current of 20mA. 10ms is the threshold for the start-up transient duration, adjustable from 5ms to 20ms, determined based on the charging time constant of the transmitter's internal capacitor.

[0122] In this situation, the system determines it as a normal power-on process and does not perform a disconnection operation, allowing the current to drop naturally. Conversely, if the current continues to exceed 40mA or the over-limit time exceeds 10ms, it is determined to be a hard short-circuit fault, and the disconnection protection is immediately triggered.

[0123] Step 404: If the measurement is in a steady state, determine whether the abnormal fluctuation exceeds the safety threshold. If so, immediately trigger the disconnection protection.

[0124] In other words, if the measurement is in a steady state, it determines whether the abnormal fluctuation exceeds the preset safety threshold. If so, it immediately triggers the disconnection protection and stops the subsequent acquisition and correction processing.

[0125] In this embodiment, when the system is in a steady-state measurement state, the circuit should not experience significant current fluctuations. The safety threshold is set more strictly at this time, for example, 22mA. Once a current exceeding this threshold is detected, the system determines it as an overcurrent fault during operation, and without waiting for debouncing, disconnects the relay to protect the precision sampling resistor and power module.

[0126] Among them, the state-based protection logic not only ensures the success rate of power-on but also guarantees safety under steady-state conditions.

[0127] On the other hand, the safety threshold should be set between 21mA and 25mA, slightly higher than the transmitter's maximum operating current of 20mA, with a safety margin. For example, it can be set to 22mA.

[0128] After performing the collaborative protection determination, parameter adaptive feedback is also included, specifically:

[0129] Step 405: When the disconnection protection is triggered, identify the fault type that caused the abnormal fluctuation.

[0130] In this embodiment, the MCU records a snapshot of the fault scene while performing protection actions, thereby identifying the fault type. The system defines several fault codes, such as: HARD_SHORT (hard short circuit), characterized by a sharp drop in voltage to near 0V and a continuous overcurrent; COMPLIANCE_LOW (insufficient compliance), characterized by a current that has not reached the set value but the voltage has been pulled down to the non-linear region; and OPEN_LOOP (open circuit), characterized by normal voltage but current close to 0mA. For example, if the recorded data shows that the voltage drops instantly from 24V to 2V at power-on, it is identified as a hard short circuit.

[0131] According to one aspect of this application, arbitration is performed on abnormal fluctuations triggered simultaneously by multiple channels to distinguish between single-channel faults and system-level voltage dips. In this embodiment, since all channels share the same power module, a sudden increase in the total load may cause a short-term dip in the common bus voltage, resulting in all operating channels simultaneously detecting voltage drops and current fluctuations. To avoid misjudging such system-level disturbances as independent faults of individual channels and causing group failures, the MCU executes global arbitration logic.

[0132] When the MCU detects that more than N (e.g., 3) channels report a COMPLIANCE_LOW or undervoltage event within the same time window, the system determines that a system-level voltage drop is occurring. In this case, the MCU does not disconnect the individual channels but instead activates a system-level voltage regulation strategy. This could involve temporarily raising the output voltage setpoint of the main power supply, or prioritizing the disconnection of channels in the RAMP state (not yet stable) while protecting channels in the STABLE state (currently measuring). Independent protection actions for each channel are only executed when the event is determined to be non-system-level.

[0133] Step 406: If the fault type is identified as insufficient compliance, a parameter adjustment instruction is generated. The parameter adjustment instruction is used to increase the target supply voltage for the next time or extend the soft start ramp parameter.

[0134] In other words, it is used to increase the target supply voltage for the next execution of connection control.

[0135] In this embodiment, the system has self-healing capabilities for soft faults related to non-compliance. For example, if an attempt to drive a high-impedance transmitter with a 12V power supply fails and is identified as a non-compliance issue, the system will generate a parameter adjustment command. This command will modify the configuration parameters of the channel, either increasing the target voltage to 24V or extending the soft-start ramp time from 50ms to 200ms.

[0136] Step 407: Feedback the parameter adjustment command to the configuration system to update the control strategy for the target channel.

[0137] Correspondingly, the generated parameter adjustment instructions are written to the MCU's non-volatile configuration area. When the device performs power supply configuration for that channel again, it will directly read the updated strategy. For example, the system will automatically start at 24V, preventing the recurrence of the fault. This closed-loop feedback mechanism enables intelligent operation and maintenance of the device, reducing the need for manual intervention.

[0138] According to one aspect of this application, before performing specific collaborative protection decisions, the system also introduces a global power supply capacity budget P. _budget Or current budget I _budget As a constraint, the MCU accumulates the expected power consumption of all enabled channels in real time to calculate the total power P. _total If P is detected _total Approaching P _budget (For example, when the rated power is reached to 95%), the MCU will automatically tighten the protection threshold of each channel, or prioritize the implementation of current limiting strategy for newly accessed channels in RAMP state, in order to ensure the stability of the system bus voltage and prevent system-level voltage drop due to insufficient total budget.

[0139] On the one hand, the formula for calculating the total power budget of the system can be:

[0140] P _total =∑(S _i ×V _i ×I _i );

[0141] Among them, P _total The current total system power (unit: mW); ∑ represents the summation over all channels i in the system; S _i This represents the switch state of channel i, where 1 indicates on and 0 indicates off; V _i I represents the current supply voltage for channel i; _i This represents the current loop current of channel i.

[0142] On the other hand, a collaborative protection judgment value example is provided. Assuming that the current channel is in a ramping state, the detected current peak is 35mA and the duration is 8ms. Since 35mA is less than 40mA and 8ms is less than 10ms, it meets the characteristics of startup transient. Therefore, the current connection state is maintained and disconnection protection is not triggered.

[0143] In other scenarios, assuming the current channel is in ramp-up mode (RAMP), the power supply output voltage is rising from 0V at a slope of 0.5V / ms. At 15ms after power-on, the MCU detects an abnormal fluctuation in the loop current, with a peak value reaching 35mA, exceeding the steady-state safety threshold of 22mA.

[0144] At this point, the MCU reads the current state variable `State`, confirms it's in RAMP state, and thus enters the transient characteristic determination branch. The system begins recording the duration of the abnormal fluctuation. After 8ms of continuous monitoring, the current peak remained around 35mA, then began to naturally decrease.

[0145] Based on the preset start-up transient characteristic criteria, since 35mA is less than the peak threshold of 40mA and 8ms is less than the duration threshold of 10ms, the system determines that the current abnormal fluctuation is consistent with the normal power-on process caused by the charging of the transmitter's internal capacitor. Therefore, the current connection status is maintained, the disconnection protection is not triggered, and the soft start is allowed to continue.

[0146] If, under the same conditions, the peak current reaches 45mA or the duration exceeds 15ms, the system determines it to be an abnormal short-circuit fault, triggers the disconnection protection, and disconnects the relay to protect the circuit.

[0147] Another example describes an optional implementation of a bivariate coupling error compensation model and its offline construction method, particularly a method based on the bivariate coupling error compensation of supply voltage and loop current. This method overcomes the limitation of traditional calibration that only considers the single variable of current by introducing supply voltage as a second-dimensional variable, thus eliminating measurement errors caused by voltage fluctuations in multi-channel shared power supply architectures. Furthermore, its mathematical model, numerical calculation examples, and offline parameter construction process are also provided.

[0148] Correspondingly, in the common power supply loop, the measurement error ε is not only a function of the current I, but also a function of the supply voltage V. Traditional calibration models assume ε = f(I), while the three-dimensional model established in this embodiment is ε = f(I, V). The specific compensation model adopts the voltage sensitivity coefficient method, which assumes that at a certain current point, the error has a linear relationship with the voltage change, while the slope of this linear relationship, i.e., the voltage sensitivity coefficient, has a non-linear relationship with the current change.

[0149] Step 501: Acquire the raw electrical signals in the power supply circuit, specifically including:

[0150] The loop current value flowing through the power supply loop is collected in real time; the power supply voltage value of the target channel at the current moment is obtained; and the loop current value and power supply voltage value are used as the raw electrical signal.

[0151] In this embodiment, the signal acquisition module simultaneously samples two physical quantities. The loop current value is obtained by reading the voltage drop across the sampling resistor using a 24-bit high-precision ADC and converting it, with the unit being mA. The supply voltage value is obtained by reading it through a resistor divider network and the ADC, with the unit being V. The synchronously acquired loop current value and supply voltage value constitute the input pair (I, V) for subsequent algorithms.

[0152] The voltage sensitivity coefficient is obtained through the following pre-executed model construction:

[0153] Step 502: In the offline calibration stage, select multiple standard current points for the measurement channel.

[0154] In this embodiment, a one-time offline calibration is required before shipment to build the model. A high-precision standard current source is connected to the measurement channel, and key points that can cover the measurement range are selected as standard current points. For example, the following characteristic points are selected: low point 4.000mA, mid point 12.000mA, and high point 20.000mA.

[0155] Step 503: For each standard current point, measure the error data under different supply voltage conditions and calculate the discrete voltage sensitivity coefficient corresponding to that standard current point.

[0156] In this embodiment, for each selected standard current point, the external programmable power supply is adjusted or the device's own load switching function is used to change the supply voltage. For example, for the standard point of 20.000mA, the measurement error is recorded under two conditions: a voltage of 24.5V and 23.5V.

[0157] Assume the error ε is measured at 24.5V. _high The current is 0.005mA, and the error ε is measured at 23.5V. _low The current is 0.003mA. Therefore, the discrete voltage sensitivity coefficient b at this current point is... _k The calculation can be:

[0158] b _k =(ε _high -ε _low ) / (V _high -V _low )=(0.005-0.003) / (24.5-23.5)=0.002mA / V.

[0159] On the other hand, the formula for calculating the discrete voltage sensitivity coefficient is:

[0160] b _k =(ε _high -ε _low ) / (V _high -V _low );

[0161] Among them, b _k ε is the discrete voltage sensitivity coefficient at the standard current point k (unit: mA / V); _high To operate at high supply voltage V _high The measured current error; ε _low To operate at low supply voltage V _low The measured current error; V _high The high supply voltage value used for testing; V _low This is the low supply voltage value used for testing.

[0162] Step 504: A numerical fitting algorithm is used to establish a functional relationship between the discrete voltage sensitivity coefficient and the current value, and the functional relationship is stored in the calibration parameters as the calculation model of the voltage sensitivity coefficient.

[0163] Furthermore, by using a quadratic polynomial for curve fitting, the sensitivity coefficient under any current can be obtained. Let the fitting function be:

[0164] b(I)=c _0 +c _1 ×I+c _2 ×I 2 The least squares method is used to regress the data points, and the coefficient c is solved. _0 c _1 and c _2 For example, the solution is c. _0 =0.001, c _1 =0.00005, c _2 =0. The polynomial coefficients, which are the calibration parameters, are stored in memory.

[0165] Alternatively, the voltage sensitivity coefficient fitting model can be expressed as the following formula:

[0166] b(I)=c _0 +c _1 ×I+c _2 ×I 2 ;

[0167] Where b(I) is the voltage sensitivity coefficient corresponding to any current I; I is the loop current value; c _0 c represents the coefficients of the constant term obtained from the fitting. _1 c represents the coefficients of the first-order term obtained from the fitting; _2 The coefficients of the quadratic term obtained from the fitting are denoted as .

[0168] Based on this, the original electrical signal is corrected using calibration parameters, specifically including:

[0169] Step 505: Call the error compensation model, which defines the coupling relationship between measurement error and loop current and supply voltage.

[0170] In this embodiment, during real-time measurement, the MCU reads coefficient c from the memory. _0 c _1 c _2 and reference voltage V _0 For example, at 24.0V, an error compensation model is reconstructed.

[0171] Step 506: Input the loop current value and the supply voltage value into the error compensation model to calculate the dynamic error compensation amount caused by the fluctuation of the supply voltage.

[0172] The specific calculation logic of the error compensation model includes:

[0173] Obtain the reference voltage of the power supply circuit under no-load conditions, and determine the voltage sensitivity coefficient corresponding to the circuit current value;

[0174] Calculate the difference between the supply voltage and the reference voltage to obtain the voltage deviation.

[0175] Multiplying the voltage sensitivity coefficient by the voltage deviation yields the dynamic error compensation amount.

[0176] Accordingly, the formula for calculating the real-time voltage sensitivity coefficient is as follows:

[0177] b _current =c _0 +c _1 ×I _raw +c _2 ×I _raw 2 ;

[0178] Among them, b _current I represents the voltage sensitivity coefficient under the current measured current. _raw This represents the currently acquired raw current value; c _0 c _1 c _2 These are the pre-stored model coefficients.

[0179] Furthermore, the voltage deviation can be calculated using the following formula:

[0180] ΔV=V _meas -V _0 ;

[0181] Where ΔV is the voltage deviation; V _meas This is the currently collected power supply voltage value; V _0 This is the reference voltage value, which is usually the no-load voltage.

[0182] Furthermore, the dynamic error compensation amount can be calculated using the following formula:

[0183] Δε=b _current ×ΔV;

[0184] Where Δε is the calculated error compensation amount caused by voltage fluctuation (unit: mA); b _current ΔV is the voltage sensitivity coefficient under the current; ΔV is the voltage deviation.

[0185] In this embodiment, the real-time voltage sensitivity coefficient under the current current is calculated. Assume the currently acquired I... _raw For 10mA, substituting into the polynomial: b _current =0.001+0.00005×10+0=0.0015mA / V.

[0186] Next, calculate the voltage deviation ΔV = V _meas -V _0 Assume the current measured voltage V _meas It is 23.0V, and the reference voltage is V. _0 If the voltage is 24.0V, then ΔV = -1.0V.

[0187] Based on this, the dynamic error compensation amount Δε is calculated. Specifically, Δε = b _current ×ΔV=0.0015×(-1.0)=-0.0015mA.

[0188] Step 507: Compensate the loop current value using dynamic error compensation to obtain the target measurement value.

[0189] In this embodiment, the final correction formula is:

[0190] I _corrected =I _raw -Δε;

[0191] Among them, I _corrected The target measurement value after bivariate correction; I _raw The original current value is given; Δε is the dynamic error compensation amount. Substituting these values ​​into the calculation, we get I... _corrected =10.000-(-0.0015)=10.0015mA. This compensation eliminates the 0.0015mA system error introduced by the 1V drop in supply voltage.

[0192] According to one aspect of this application, as an alternative implementation of bivariate coupled calibration, an online gain and zero-point update mechanism based on a two-point method is provided. That is, when a channel enters the STABLE state and meets the calibration triggering conditions (such as the first startup of the day or temperature drift exceeding a threshold), the system automatically enters the online calibration mode.

[0193] The MCU controls the power supply output, sequentially generating two reference current points, namely the first reference current point I, which is close to 4mA. _ref1 and the second reference current point I close to 20mA _ref2 Record the corresponding measured values ​​I. _meas1 and I _meas2 The calibration parameters are updated in real time using a two-point fitting formula, namely:

[0194] Gain coefficient K=(I _ref2 -I _ref1 ) / (I _meas2 -I _meas1 );

[0195] Zero-point coefficient B=I _ref1 -K×I _meas1 ;

[0196] The updated K and B will be immediately applied to subsequent measurement correction formulas, i.e., I _i_correct =K×I _i_stable +B; where I _i_correct This is the current calibration correction value for the i-th measurement, i.e., the accurate current value after gain and zero-point compensation; I _i_stable The value is the raw current measurement obtained in the i-th steady-state measurement, without calibration correction.

[0197] At the same time, the MCU will also calculate the residual of the two-point fitting as a confidence index. If the confidence is too low, the update will be abandoned and an alarm will be triggered.

[0198] On the other hand, the gain coefficient calibration formula can also be:

[0199] K=(I _std2 -I _std1 ) / (I _meas2 -I _meas1 );

[0200] Where K is the calculated gain coefficient; I _std2 This is the output value of a high-point standard current source, for example, 20mA; I _std1 This is the output value of a low-point standard current source, for example, 4mA; I _meas2 The original current value measured by the device when the input high-point standard current is applied; I _meas1 This is the original current value measured by the device when the input is a low-point standard current.

[0201] Another example provides an exemplary scheme for a self-disturbance parameter calibration method based on multi-channel load switching. This method can obtain the voltage sensitivity coefficient without the need for an external precision adjustable power supply. It utilizes the structural characteristics of the multi-channel device itself and achieves self-calibration by artificially creating voltage fluctuations on the power bus through program control of the on / off state of the load of each channel.

[0202] Specifically, the device integrates analog loads, such as a controllable 250Ω resistor connected in parallel to each channel, or uses a standard transmitter as the load. Self-disturbance calibration utilizes the load regulation characteristics of the power module to induce minute changes in the output voltage by altering the total load current.

[0203] Accordingly, the voltage sensitivity coefficient is determined through a self-disturbance calibration process, which includes:

[0204] Step 601: While keeping the input signal of the target channel constant, connect or disconnect the analog load to other measurement channels in the control device besides the target channel to change the total load current of the power supply module.

[0205] In this embodiment, channel 1 is assumed to be the target channel to be calibrated, and a constant 12mA standard signal source is connected. The MCU enters self-disturbance calibration mode and automatically executes the action sequence. Correspondingly, all relays controlling channels 2 to 8 are disconnected, at which point the power supply is in a light-load state, and the total load current is minimized.

[0206] Furthermore, all relays in control channels 2 to 8 are closed, connecting a simulated full-scale load. At this time, the power supply is under heavy load, and the total load current is at its maximum.

[0207] Step 602: Collect the first and second supply voltages of the target channel under different total load currents, as well as the corresponding first and second measured values.

[0208] In this embodiment, under light load conditions, the MCU collects the power supply voltage of channel 1, which is denoted as the first power supply voltage V. _high For example, 24.10V; simultaneously, the current reading of channel 1 is acquired and recorded as the first measured value I. _meas_1 For example, 12.005mA.

[0209] Under heavy load, the supply voltage will naturally decrease due to the internal resistance of the power supply and the voltage drop across the line. At this time, the MCU collects the voltage of channel 1 and records it as the second supply voltage V. _low For example, 23.80V; simultaneously, the current reading is collected and recorded as the second measured value I. _meas_2 For example, 12.002mA.

[0210] Step 603: Calculate the voltage sensitivity coefficient based on the difference between the first and second measured values, and the difference between the first and second supply voltages.

[0211] In this embodiment, the MCU calculates the differential ratio using the two sets of data mentioned above. Voltage difference ΔV = 24.10 - 23.80 = 0.30V. Measurement difference ΔI = 12.005 - 12.002 = 0.003mA. Voltage sensitivity coefficient b = ΔI / ΔV = 0.003 / 0.30 = 0.01mA / V. In this way, the device obtains the voltage sensitivity characteristics at a specific current point using its own resources, reducing reliance on external calibration equipment.

[0212] In other words, the formula for calculating the self-disturbance voltage sensitivity coefficient is as follows:

[0213] b=(I _meas1_load -I _meas2_load ) / (V _high_load -V _low_load );

[0214] Where b is the voltage sensitivity coefficient measured by the self-perturbation method; I _meas1_load The current value measured under light load conditions; I _meas2_load The current value measured under heavy load conditions; V _high_load The supply voltage (higher value) measured under light load conditions; V _low_load This is the supply voltage (lower value) measured under heavy load conditions.

[0215] According to one aspect of this application, an alternative technical solution for supply voltage prediction based on load state vectors is described, applicable to situations where a separate voltage sensor is not configured. This solution predicts the supply voltage using a software algorithm and can be used to provide a virtual voltage input for a compensation model.

[0216] Accordingly, assuming the device omits the voltage sampling circuit for each channel for cost reasons, the MCU calculates the actual supply voltage for each channel by monitoring its own control status and current readings, combined with the physical model of the power supply.

[0217] Furthermore, the supply voltage value is obtained through the following load condition prediction, specifically:

[0218] Step 701: Obtain the current channel switch status of all measurement channels in the device, and estimate the total load current at the output of the power module based on the number of channels in the on state and the current value of each channel.

[0219] In this embodiment, the MCU maintains the channel switch state vector L=[S _1 S _2 S _8], where S _i A value of 1 indicates the channel is open, and a value of 0 indicates it is closed. Or, in other words, S... _i The binary state value represents the switching state of the i-th channel. If it is 1, it means that the i-th channel is in the open state; if it is 0, it means that the i-th channel is in the closed state. i is the channel number index, and its value range is limited to 1-8, corresponding to the 8 independent channels of the system.

[0220] The MCU iterates through the vector and accumulates the real-time current I of all enabled channels. _i Total load current I _total The calculation formula is:

[0221] I _total =∑(S _i ×I _i ),

[0222] Where i ranges from 1 to 8.

[0223] For example, if four channels are turned on, and each channel has a current of 20mA, then I _total =80mA.

[0224] In other words, the formula for estimating the total load current can be expressed as:

[0225] I _total =∑(S _i ×I _i );

[0226] Among them, I _total The total estimated current at the power output terminal; ∑ represents the summation over all channels i; S _i This represents the switch state of channel i, where 1 indicates on and 0 indicates off; I _i This represents the measured current value of channel i.

[0227] Step 702: Call the pre-configured power supply internal resistance parameters and power supply no-load voltage parameters.

[0228] Specifically, the Thevenin equivalent parameters of the power supply module are pre-measured and stored. The power supply no-load voltage parameter V... _0 The voltage is set to 24.05V, and the internal resistance parameter R of the power supply is... _source It is set to 0.5Ω. Here, the internal resistance is the equivalent value that includes the power supply output impedance and the impedance of the PCB (printed circuit board) main circuit.

[0229] Step 703: Based on the voltage drop across the power supply internal resistance caused by the total load current, calculate the predicted supply voltage and use the predicted supply voltage as the supply voltage value.

[0230] Furthermore, the calculation of the predicted supply voltage can be performed using the following formula:

[0231] V _predict =V _0 -I _total ×R _source ;

[0232] Among them, V _predict The calculated predicted supply voltage; V _0 The no-load voltage parameter of the power supply; I _total For the total estimated current; R _source These are the pre-configured power supply internal resistance parameters.

[0233] In this embodiment, the MCU calculates the voltage drop V across the internal resistance according to Ohm's law. _drop =I _total ×R _source Substituting the values, V _drop =0.08A × 0.5Ω = 0.04V. The final predicted supply voltage V _predict =V _0 -V _drop =24.05-0.04=24.01V.

[0234] Based on this, the MCU will calculate the value V _predict Directly assign to variable V _meas Substituting this into the compensation formula, compensation for voltage fluctuation errors is still achieved without increasing hardware costs.

[0235] According to another aspect of this application, a (4-20) mA transmitter multi-channel calibration device is provided, which can simultaneously calibrate up to 8 (4-20) mA transmitters and has an integrated power supply and measurement design.

[0236] Currently, sensor calibration with (4-20) mA transmitters mostly employs a method of individual power supply, individual measurement, and calibration one by one. Different power supply voltages require switching between different power sources, resulting in low efficiency. Furthermore, common transmitter wiring methods include two-wire and three-wire systems. With a large number of devices using these systems, wiring is complex and carries certain risks. Additionally, some devices only measure a specific parameter, failing to cover all parameters of this type of transmitter, including temperature, humidity, pressure, speed, and displacement.

[0237] Currently, sensor calibration with (4-20) mA transmitters typically employs a method of individual power supply, individual measurement, and individual calibration. This device achieves simultaneous calibration of up to 8 channels, using the same circuit for power supply and measurement. It incorporates a two-wire to three-wire switching design to accommodate the different operating principles of two-wire and three-wire transmitters. The power supply and measurement components are integrated into a single two- or three-wire circuit, simplifying wiring. The system can be composed of five parts: a multi-voltage power supply system, a circuit protection system, a measurement switching system, a display system, and a calibration correction system.

[0238] The multi-voltage power supply system consists of three output DC regulated power supplies: 5V, 12V, and 24V. The 5V voltage is used to drive the relay and high-precision ammeter, while the 12V and 24V voltages are used to power the transmitter being calibrated.

[0239] The circuit protection system is designed to prevent damage to the high-precision ammeter from unintentionally short-circuiting the power supply and measurement lines, as they share positive and negative terminals. To avoid this, the system integrates a 50mA glass tube fuse and a 50mA resettable fuse. The glass tube fuse breaks the circuit during overload and needs to be replaced, while the resettable fuse automatically cuts off the circuit after overload and can restore the circuit after a few minutes.

[0240] The measurement switching system comprises two parts: a transmitter power supply voltage switching system (24V to 12V), sufficient to meet the power supply needs of most transmitters; and a transmitter wiring two-wire / three-wire switching system, which meets the wiring requirements of most transmitters without requiring equipment or measurement channels to be changed. This system consists of a three-output DC regulated power supply, a single-pole double-throw switch, and relays.

[0241] The display system consists of eight high-precision ammeters with an accuracy of 0.05. Each display unit has its own start switch, which is controlled by a switching switch, and it is equipped with its own measurement terminal.

[0242] The calibration and correction system exhibits a current display reading drift, which can be corrected using an over-adjusted high-precision ammeter. A calibration interface is provided for ease of adjustment.

[0243] Furthermore, a multi-voltage power supply system supplies power to the switching switch, the conversion relay, and the high-precision digital ammeter. A measurement switching system enables switching between two-wire and three-wire systems for the measurement circuit. A circuit protection system protects the high-precision ammeter and the overall circuit from short-circuit conditions. A display system shows the measurement results, and a calibration system performs calibration corrections to show any drift.

[0244] Accordingly, the power supply system can use 5V / 12V / 24V DC regulated power supplies to power the high-precision ammeter used for measurement, the transmitter being calibrated, and the relay switch, respectively. The measurement switching module can use a double-opening double-closed switch to switch between two-wire and three-wire systems, and a double-throw switch to switch between 12V and 24V power supplies. Since the ammeter and the DC voltage power supply share two wires, a short circuit will cause current overload. The circuit protection system can use a resettable fuse for protection, realizing automatic power-off in case of overload and automatic restoration of normal circuit function. The power supply system can use a relay switch to realize single-channel measurement and double disconnection in case of power failure. When the value drifts, the calibration correction module can calibrate the digital ammeter through the calibration system.

[0245] The above achieves the effect of simultaneous power supply and measurement in the same circuit, and has circuit protection to protect both the device and the device under test. It can perform measurements on up to 8 devices at the same time.

[0246] For example, the specific measurement process can be as follows:

[0247] After connecting the 220V power supply, turn on switch 5, and select to turn on switch 3 of each channel according to the number of transmitters under test, and preheat for 15 minutes.

[0248] According to the instruction manual of the transmitter under test, select the appropriate power supply voltage (12V or 24V) using switch 6. Confirm the transmitter wiring method. If it is a two-wire connection, connect the test leads to terminal 2. For two-wire connections, connect the two left terminals, which are the red positive and black negative terminals respectively.

[0249] If a three-wire connection is used, turn on switch 4, connect the test leads to terminal 2, connect the power supply positive terminal to the red terminal, the measurement positive terminal to the green terminal, and the power supply and measurement negative terminals to the black terminal. When the transmitter receives an input signal, ammeter 1 will display the corresponding current value.

[0250] When the ammeter reading drifts, you can input a standard voltage value through terminal 2, the middle black terminal, and calibration interface 7, and then fine-tune the potentiometer on the back panel of ammeter 1 to make the displayed value consistent with the standard signal.

[0251] If the ammeter reading is abnormal, check the fuse. If the fuse is blown, replace it. If a short circuit during measurement causes the ammeter to read abnormally, and the glass tube fuse is normal, wait a few minutes for the resettable fuse to reset.

[0252] In other scenarios, users issue configuration commands via a host computer, specifying calibration channel 1, power supply level 24V, and two-wire connection mode. The system detects that the previous working channel has been completely disconnected, with a residual current of 0.05mA < 0.1mA threshold, calculates a compliance margin of 3V (> 2V), and selects a fast soft-start slope of 1V / ms.

[0253] After a 24ms soft start, the system entered steady state, acquiring an initial current of 12.000mA and a measured voltage of 23.5V. The error compensation model was then applied, calculating a voltage sensitivity coefficient of 0.0015mA / V, a voltage deviation of -0.5V, and a dynamic error compensation of -0.00075mA. The final output target measurement value was 12.00075mA, eliminating voltage fluctuation errors caused by load changes in other channels.

[0254] On the other hand, an application scenario example, especially an end-to-end scenario example, is provided to illustrate the actual execution process of the calibration method of the present invention.

[0255] Suppose a user needs to calibrate a 4-20mA pressure transmitter connected to channel 3. Currently, channel 2 is performing calibration measurements. The device has a total of 8 measurement channels.

[0256] Optionally, a configuration command can be issued. The user selects channel 3 via the host computer software, sets the power supply level to 24V, the wiring mode to two-wire, and then issues the configuration command.

[0257] Optionally, a disconnection confirmation is performed. The MCU monitors the residual loop current of channel 2, which reads 0.08mA with a current change rate of 0.02mA / ms. Since 0.08mA is less than the turn-off threshold of 0.1mA and 0.02mA / ms is less than the stability threshold of 0.05mA / ms, the system determines that channel 2 has been completely and safely disconnected and is ready for switching.

[0258] Optionally, compliance margin prediction is performed. The MCU estimates the total loop resistance to be 500Ω and the transmitter's minimum voltage drop to be 12V based on historical data from channel 3. The loop compliance voltage V is calculated based on a target current of 20mA. _req =0.02A × 500Ω + 12V = 22V. Compliance margin = 24V - 22V = 2V.

[0259] Optionally, soft-start control is implemented. Since the compliance margin is 2V, which is in the critical region, a moderate soft-start slope of 0.5V / ms is selected. The MCU controls the power supply output voltage to rise linearly from 0V at 0.5V / ms via PWM modulation. After 48ms, the output voltage reaches the target value of 24V.

[0260] Optionally, a steady-state determination is performed. The MCU continuously monitors the rate of change of current and the rate of change of voltage. After a 500ms stabilization observation window, if it is confirmed that |dI / dt|=0.001mA / ms is less than the threshold of 0.002mA / ms and |dV / dt|=0.005V / ms is less than the threshold of 0.01V / ms, the system updates the state of channel 3 to STABLE and enters the formal measurement phase.

[0261] Optionally, signal acquisition is performed. The ADC samples the loop current to obtain the raw current value I. _raw =12.003mA. Simultaneously read the current supply voltage V. _meas =23.6V.

[0262] Optionally, bivariate error compensation is performed. The MCU reads the fitting coefficients c from memory. _0 =0.001, c _1 =0.00005, c _2 =0, reference voltage V _0 =24.0V. Calculate the voltage sensitivity coefficient under the current: b _current =0.001 + 0.00005 × 12.003 = 0.0016 mA per volt. Calculate the voltage deviation: Delta_V = 23.6 - 24.0 = -0.4V. Calculate the dynamic error compensation: Delta_ε = 0.0016 × (-0.4) = -0.00064 mA.

[0263] Optionally, execute the output target measurement. Final corrected target measurement: I _corrected =12.003-(-0.00064)=12.00364mA. This value is displayed in real time on the screen and uploaded to the host computer for recording.

[0264] Therefore, the influence of power supply voltage fluctuations caused by other channels (such as channels 1, 4, and 5 being in operation) on the measurement accuracy of channel 3 is eliminated, which can be used to achieve high-precision calibration.

[0265] In this application, a two-variable coupling error compensation calibration method is adopted, which breaks through the limitations of traditional single-variable calibration. A two-dimensional error model of power supply voltage and loop current is established to calculate and compensate for nonlinear voltage fluctuation errors caused by load changes or line impedance in real time, thereby improving measurement accuracy without the need for an external precision voltage regulator.

[0266] Furthermore, the embodiment employs a non-disruptive switching timing control and collaborative protection strategy. It introduces compliance margin prediction and adaptive soft-start technology to eliminate surge impacts and voltage drops caused by hard switching; combined with event-driven disconnection confirmation and state machine context discrimination mechanism, it distinguishes between normal startup transients and real fault events; and it introduces global budget constraints to prevent false triggering of protection mechanisms and unexpected power outages of the device under test.

[0267] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A calibration method for a multi-channel transmitter calibration device, characterized in that, include: In response to the configuration command for the target channel, the connection status between the power module and the target channel is controlled to put the target channel into working state and obtain the power supply circuit for the target channel; In operation, the raw electrical signals in the power supply circuit are collected; Based on the original electrical signal, the original electrical signal is corrected using calibration parameters, and the target measurement value of the target channel is output. Specifically, controlling the connection status between the power supply module and the target channel includes: determining the target supply voltage of the target channel and obtaining the loop compliance voltage required to maintain the current load of the target channel; calculating the difference between the target supply voltage and the loop compliance voltage to obtain the compliance margin; determining the soft-start ramp parameters based on the compliance margin, and controlling the output voltage of the power supply module to gradually increase according to the soft-start ramp parameters until the target supply voltage is reached; specifically, obtaining the loop compliance voltage required to maintain the current load of the target channel involves: performing two-point sampling near the current operating point using a small voltage disturbance; constructing an equivalent volt-ampere characteristic model of the loop using the two-point data, extrapolating it to the target current, and estimating the minimum terminal voltage required to maintain the target current; The process of acquiring raw electrical signals from the power supply circuit includes: acquiring the circuit current value flowing through the power supply circuit in real time; obtaining the power supply voltage value of the target channel at the current moment; and using the circuit current value and the power supply voltage value as raw electrical signals. The process of correcting the original electrical signal using calibration parameters includes: calling the error compensation model, which defines the coupling relationship between measurement error and loop current and supply voltage; inputting the loop current value and supply voltage value into the error compensation model to calculate the dynamic error compensation amount caused by supply voltage fluctuations; and using the dynamic error compensation amount to compensate the loop current value to obtain the target measurement value. The error compensation model is constructed based on calibration parameters. The specific calculation logic of the error compensation model includes: obtaining the reference voltage of the power supply circuit under no-load conditions, determining the voltage sensitivity coefficient corresponding to the circuit current value; calculating the difference between the power supply voltage value and the reference voltage to obtain the voltage deviation; and multiplying the voltage sensitivity coefficient by the voltage deviation to obtain the dynamic error compensation amount.

2. The method according to claim 1, characterized in that, The voltage sensitivity coefficient is determined through a self-disturbance calibration process, which includes: While keeping the input signal of the target channel constant, the other measurement channels in the control device, besides the target channel, are connected to or disconnected from the analog load to change the total load current of the power module. The first and second supply voltages of the target channel under different total load currents were collected, along with the corresponding first and second measured values. The voltage sensitivity coefficient is calculated based on the difference between the first and second measured values, and the difference between the first and second supply voltages.

3. The method according to claim 1, characterized in that, The supply voltage value is obtained by predicting the following load conditions, specifically: The current channel switch status of all measurement channels in the device is obtained. Based on the number of channels in the on state and the current value of each channel, the total load current at the output of the power module is estimated. Call the pre-configured power supply internal resistance parameters and power supply no-load voltage parameters; The predicted supply voltage is calculated based on the voltage drop across the power supply's internal resistance caused by the total load current, and this predicted supply voltage is used as the supply voltage value.

4. The method according to claim 1, characterized in that, The method also includes exception protection, specifically including: Real-time monitoring of the current timing status of the target channel, including the ramp-up state where the power supply voltage is rising and the steady-state measurement state where the power supply voltage has stabilized; When an abnormal fluctuation in the current in the power supply circuit is detected, a coordinated protection decision is made based on the current timing status. If the system is in a ramping state, determine whether the abnormal fluctuations meet the characteristics of a startup transient. If so, maintain the current connection state; otherwise, trigger disconnection protection. If the measurement is in a steady state, determine whether the abnormal fluctuation exceeds the safety threshold. If so, immediately trigger the disconnection protection.

5. The method according to claim 1, characterized in that, The voltage sensitivity coefficient is obtained through the following pre-executed model construction: During the offline calibration phase, multiple standard current points are selected for the measurement channel; For each standard current point, error data are measured under different supply voltage conditions, and the discrete voltage sensitivity coefficient corresponding to that standard current point is calculated. A numerical fitting algorithm is used to establish a functional relationship between the discrete voltage sensitivity coefficient and the current value, and the functional relationship is stored in the calibration parameters as a calculation model for the voltage sensitivity coefficient.

6. The method according to claim 1, characterized in that, Before controlling the connection status between the power module and the target channel, an event-driven disconnection confirmation is also included, specifically: Real-time monitoring of the residual loop current and its rate of change in the previous working channel; Determine whether the residual loop current is less than the preset turn-off current threshold and whether the absolute value of the current change rate is less than the preset stability threshold. Connection control for the target channel is executed only if all of the above conditions are met; otherwise, the system remains in a waiting state.

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