Multi-channel instrument calibration device control circuit

Abstract

The invention belongs to the technical field of instrument calibration, and relates to a multichannel instrument calibration device control circuit. The multi-channel instrument calibration device control circuit comprises instrument circuits which are arranged in parallel between power supply terminals, each instrument circuit comprises a channel power supply diode and an instrument which are sequentially connected in series, one end of an electric signal output end is connected with a positive electrode of a power supply, and the other end of the electric signal output end is connected with the instrument through a channel selection switch circuit. The multi-channel instrument checking method has the remarkable effects of simplifying the working steps of multi-channel instrument checking, reducing the risk of damage of instrument terminals, greatly reducing the time for checking a plurality of instruments at the same time, improving the working efficiency, reducing the labor cost and improving the enterprise income.

Description

Technical Field

[0001] The invention belongs to the technical field of instrument calibration, and relates to a control circuit of a multi-channel instrument calibration device. Background Art

[0002] At present, the conventional instrument calibration method is to calibrate a single instrument one by one through a calibrator. To improve work efficiency, the pressure source can be divided into multiple channels through a multi-interface calibration bench, and multiple instruments can be calibrated simultaneously.

[0003] When using a multi-interface calibration bench, for instruments with electrical signal outputs such as pressure transmitters and pressure switches, when a certain pressure to be tested is reached, it is necessary to connect to different instruments one by one through the electrical signal interface of the external calibrator.

[0004] This method requires each instrument to be connected to the calibrator's electrical signal interface once at each pressure calibration point, which involves a large number of repetitive operations and frequent removal and connection of signal lines, making the efficiency very low. In addition, after the calibrator's signal interface is connected to the instrument, the value can only be read after the instrument is powered on and initialized. The time for the instrument to be powered on and initialized varies from a few seconds to tens of seconds depending on the instrument model. Summary of the invention

[0005] The present invention aims at the defects of the prior art and provides a control circuit for a multi-channel instrument calibration device.

[0006] The present invention is implemented as follows: a multi-channel instrument calibration device control circuit, which includes instrument circuits arranged in parallel between power supply terminals, wherein each instrument circuit includes a channel power supply diode and an instrument connected in series in sequence, one end of the electrical signal output end is connected to the positive electrode of the power supply, and the other end is connected to the instrument through a channel selection switch circuit.

[0007] A multi-channel instrument calibration device control circuit as described above, wherein the power supply terminals are a 24V power supply positive terminal and a 24V power supply negative terminal, one end of the electrical signal output end is connected to the 24V power supply positive terminal, and the other end is connected to the instrument through a channel selection switch.

[0008] A multi-channel instrument calibration device control circuit as described above, wherein one end of the channel power supply diode of the instrument circuit is connected to the positive terminal of the 24V power supply, and the other end is connected to the instrument, and the other end of the instrument is connected to the negative terminal of the 24V power supply through the channel power supply protection circuit.

[0009] In the control circuit of a multi-channel instrument calibration device as described above, the channel power supply protection circuit includes a channel power supply circuit and a channel protection circuit connected in parallel.

[0010] A control circuit of a multi-channel instrument calibration device as described above, wherein the channel power supply circuit includes a channel power supply current limiting resistor, one end of the channel power supply current limiting resistor is connected to the instrument, and the other end is connected to the drain of the channel power supply MOS tube, the gate of the channel power supply MOS tube is connected to the channel power supply signal input terminal through the channel power supply signal current limiting resistor, the source of the channel power supply MOS tube is connected to the negative terminal of the 24V power supply, and the gate of the channel power supply MOS tube is also connected to the negative terminal of the 24V power supply through the channel power supply signal pull-down resistor.

[0011] A control circuit of a multi-channel instrument calibration device as described above, wherein the channel protection circuit includes a protection signal current limiting resistor, one end of the protection signal current limiting resistor is connected to the instrument, and the other end is connected to the voltage stabilizing filter circuit, and the protection signal current limiting resistor is also connected to the protection signal output terminal.

[0012] A control circuit of a multi-channel instrument calibration device as described above, wherein the voltage stabilizing and filtering circuit includes a discharge resistor, a voltage stabilizing diode, and a filtering capacitor connected in parallel, wherein the positive electrode of the voltage stabilizing diode is connected to the negative terminal of the 24V power supply.

[0013] A multi-channel instrument calibration device control circuit as described above, wherein the channel selection switch circuit includes a channel selection switch power supply arranged between the positive terminal of a 24V power supply and the negative terminal of a 24V power supply, and a channel selection relay contact arranged in each instrument circuit.

[0014] A control circuit of a multi-channel instrument calibration device as described above, wherein the channel selection switch power supply includes a channel selection relay coil and a channel selection MOS tube connected in series, wherein the channel selection relay coil corresponds to the channel selection relay contact and controls the on and off of the channel selection relay contact, the channel selection relay coil is connected to the drain of the channel selection MOS tube, the source of the channel selection MOS tube is connected to the negative terminal of the 24V power supply, the gate of the channel selection MOS tube is connected to the negative terminal of the 24V power supply through the channel selection signal pull-down resistor, and the gate of the channel selection MOS tube is also connected to the channel selection signal current limiting resistor.

[0015] The significant effects of the present invention are: simplifying the work steps of multi-channel instrument calibration, reducing the risk of instrument terminal damage, greatly reducing the time for simultaneous calibration of multiple instruments, improving work efficiency, reducing labor costs, and increasing corporate profits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a simplified schematic diagram of channel selection and power supply;

[0017] Figure 2 It is the control circuit schematic diagram of the multi-channel instrument calibration device.

[0018] In the figure: 1. Channel selection signal current limiting resistor, 2. Channel selection signal pull-down resistor, 3. Channel selection MOS tube, 4. Relay freewheeling diode, 5-1. Channel selection relay coil, 5-2. Channel selection relay contact, 6. Channel selection signal input terminal, 7. Channel power supply signal current limiting resistor, 8. Channel power supply signal pull-down resistor, 9. Channel power supply MOS tube, 10. Channel power supply diode, 11. Channel power supply current limiting resistor, 12. Instrument electrical signal interface, 13. Channel power supply signal input terminal, 14. Protection signal current limiting resistor, 15. Zener diode, 16. Filter capacitor, 17. Discharge resistor, 18. Protection signal output terminal, 19. Electrical signal output terminal, 20. 24V power supply positive terminal, 21. 24V power supply negative terminal. DETAILED DESCRIPTION

[0019] Part I:

[0020] The circuit is mainly divided into three parts: channel selection, channel power supply and channel protection.

[0021] Serial number 1-6 is the channel selection circuit part, which receives the channel selection signal of the microcontroller and is responsible for selecting the instrument electrical signal of the channel for output. The microcontroller software realizes that only one channel is selected at the same time.

[0022] Serial number 7-13 is the channel power supply circuit part, which receives the channel power supply signal of the microcontroller and is responsible for powering the instrument connected to the channel.

[0023] Serial numbers 14-18 are the channel protection circuit part, which outputs the detected channel current status signal to the microcontroller. The microcontroller determines whether there is an overload, short circuit or other fault in the channel based on the signal. If there is an abnormality, it outputs a signal to cut off the power supply of the channel.

[0024] Serial number 1-18 is a circuit component of one channel. A multi-channel control circuit has a circuit composed of multiple of the above components. Figure 2 The components of two channels are drawn in, but they are not marked repeatedly.

[0025] After the instrument electrical signals of all channels pass through the selection switch, they are output to the external standard device through the signal output terminal (serial number 18).

[0026] The specific functions of each component are as follows:

[0027] 1. Channel selection signal current limiting resistor: protects the microcontroller IO pins to prevent damage due to overcurrent driving, and prevents the MOS tube circuit from being abnormal and causing damage to the microcontroller IO pins.

[0028] 2. Channel selection signal pull-down resistor: When there is no signal output from the microcontroller, it eliminates external interference and ensures that the MOS tube is reliably shut down.

[0029] 3. Channel selection MOS tube: receives the signal from the microcontroller, is responsible for connecting or disconnecting the channel selection circuit, and controls the power supply or power-off of the relay coil.

[0030] 4. Relay freewheeling diode: absorbs the reverse electromotive force generated when the relay coil loses power, protects peripheral components, and reduces the electromagnetic interference of the reverse electromotive force.

[0031] 5-1. Channel selection relay coil: generates a magnetic field when powered on, closing the contacts.

[0032] 5-2. Channel selection relay contacts: When the contacts are closed, the two ends of the contacts are short-circuited to output the electrical signal of the corresponding channel instrument.

[0033] 6. Channel selection signal input terminal: receives the channel selection signal from the microcontroller.

[0034] 7. Channel power supply signal current limiting resistor: function is the same as 1.

[0035] 8. Channel power supply signal pull-down resistor: function is the same as 2.

[0036] 9. Channel power supply MOS tube: receives the signal from the microcontroller and is responsible for connecting or disconnecting the channel power supply circuit.

[0037] 10. Channel power supply diode: Each power supply channel is equipped with 2 diodes to generate a voltage drop of about 1.4V across the diode when power is supplied, providing the basic condition for extracting channel signals.

[0038] 11. Channel power supply current limiting resistor: prevents the signal line or terminal connected to the instrument from being short-circuited, causing instantaneous large current and damaging components in the circuit.

[0039] 12. Instrument electrical signal interface: Connect the instrument electrical signal terminal to power the instrument and introduce the output signal of the instrument.

[0040] 13. Channel power supply signal input terminal: receives the channel power supply signal of the microcontroller.

[0041] 14. Protective signal current limiting resistor: When the signal line or terminal connected to the instrument is short-circuited, or there is transient high voltage interference, the upper end voltage of 14 is very high. At this time, the signal amplitude output to the microcontroller is limited by 14.

[0042] 15. Zener diode: When there is a high voltage at the upper end of the current limiting resistor 14 for a long time, the Zener diode is turned on, clamping the signal output to the microcontroller at the reverse conduction voltage value of the diode. The diode voltage value should be less than or equal to the maximum allowable output voltage of the microcontroller pin. For a microcontroller with an operating voltage of 5V, the diode voltage value can be 3.3V.

[0043] 16. Filter capacitor: When there is a transient high voltage at the upper end of the current limiting resistor 14, 14 and 16 form a low-pass filter, which can prevent the signal output to the microcontroller from transient mutations. According to experience, the capacitor can be 0.1uF.

[0044] 17. Discharge resistor: When the device is powered off or the circuit works in the pressure switch mode, the voltage across the capacitor 16 is discharged. The resistor can take a larger resistance value, such as 1M ohm.

[0045] 18. Protection signal output terminal: In transmitter working mode, it outputs overcurrent or short circuit protection signal; in pressure switch working mode, it outputs pressure switch closing signal.

[0046] 19. Electrical signal output terminal: Output the selected pressure transmitter current signal to an external standard.

[0047] 20.24V power supply positive terminal: positive power supply for the circuit.

[0048] 21.24V power supply negative terminal: negative power supply terminal of the circuit.

[0049] Part II:

[0050] Through the channel selection circuit part of the circuit, the instrument signal switching based on the microcontroller is realized, avoiding the work of frequently removing and connecting the signal lines.

[0051] The instrument is powered by the channel power supply circuit, and the instrument maintains continuous power supply regardless of whether the channel signal is selected, thereby avoiding the process of frequent power-on and frequent waiting for initialization of the instrument.

[0052] Through the channel protection circuit part, the detection of transmitter faults such as overcurrent and short circuit is realized, and the channel power supply is timely cut off by the microcontroller to achieve the purpose of protection; at the same time, this part of the circuit is also used as a detection circuit for the pressure switch signal, so that the control circuit is not only suitable for 4-20mA analog signal instruments (such as pressure transmitters), but also for switch signal instruments (such as pressure switches).

[0053] Part III:

[0054] Through other human-machine interaction methods, the working mode signal is input to the microcontroller. The selectable working modes include "pressure transmitter" and "pressure switch". The working principle of the control circuit in different modes is as follows:

[0055] 1. Pressure transmitter mode:

[0056] 1) Channel power supply circuit:

[0057] The microcontroller outputs a "channel power supply" signal to the channel power supply signal input terminal 13, and drives the MOS tube 9 to conduct through the current limiting resistor 7. At this time, the instrument connected to the instrument electrical signal interface 12 is connected to the instrument positive electrode through the power supply positive terminal 20 and two power supply diodes 10, and the instrument negative electrode is connected to the power supply negative electrode 21 through the current limiting resistor 11 and the MOS tube 9, thereby realizing the power supply of the instrument.

[0058] 2) Channel selection circuit:

[0059] The microcontroller outputs a "channel selection" signal to the channel power supply signal input terminal 6, which drives the MOS tube 3 to conduct through the current limiting resistor 1, and the coil 5-1 of the relay 5 is energized and the contact 5-2 is attracted. At this time, the instrument connected to the instrument electrical signal interface 12 is connected to the positive electrode of the instrument through the positive power supply terminal 20, the external standard device (similar to the ammeter) connected to the signal output terminal 19, and the contact 5-2. The two power supply diodes 10 are cut off because the voltage drop across them is less than 1.4V. At this time, the current flowing through the instrument is equal to the current flowing through the external standard device, and the current signal in the instrument is measured.

[0060] To explain in detail the instrument current flow path after selecting a channel’s current signal as output, refer to the attached Figure 1 After actual measurement of current measurement by standard instruments or multimeters on the market (equivalent to the attached Figure 1 The internal resistance of the mA meter in the circuit is less than 50 ohms. Assuming that the channel is selected and the 5-2 contact is closed, the two diodes 10 are completely removed. According to the maximum current of the transmitter of 20mA, the voltage drop across the mA meter is 1V, which is less than the conduction voltage drop of the two diodes. The actual situation is that after the 5-2 contact is closed, the two diodes still exist, but because the voltage across them is less than the conduction voltage of 1.4V, the current flowing through the diodes is 0mA, that is, all the current flows through the instrument of the corresponding channel after passing through the mA meter, realizing the measurement of the instrument current of the selected channel. At the moment when the contact 5-2 is closed or disconnected, the instrument is either connected to the positive pole of the power supply through mA or connected to the positive pole of the power supply through two diodes 10, so the instrument can ensure continuous power supply.

[0061] 3) Channel protection circuit:

[0062] When the circuit is working, the negative pole of the transmitter is connected to the negative pole of the power supply through two paths, namely the path of the power supply current limiting resistor 11 and the MOS tube 9 and the path of the current limiting resistor 14 and the discharge resistor 17. When designing the circuit, the power supply current limiting resistor 11 is about 100 ohms, the protection signal current limiting resistor is about 5.1K ohms, and the discharge resistor is about 1M ohms. The former is much smaller than the latter, and the current value of the latter path will be ignored when describing the principle. Since the resistance of the current limiting resistor 14 is much smaller than the discharge resistor 17, the voltage signal output by the protection signal output terminal 18 can be equivalent to the voltage of the negative terminal of the transmitter.

[0063] When the instrument is abnormal or overload current occurs (Zener diode 15 is not conducting), terminal 18 outputs a voltage signal corresponding to the actual current; when the instrument signal terminal is short-circuited, Zener diode 15 is conducting, and terminal 18 outputs the clamping voltage value of the Zener diode.

[0064] The microcontroller detects the protection signal in real time. When the voltage signal output by the protection signal output terminal 18 is higher than the set value, it indicates that there is an overload or short circuit fault. The microcontroller immediately outputs a signal to disconnect the "channel power supply" to achieve overload and short circuit protection.

[0065] 2. Pressure switch mode:

[0066] 1) Channel power supply circuit:

[0067] The "channel power supply" signal of the microcontroller is cleared, and the MOS tube 9 is reliably turned off under the action of the pull-down resistor 8 and the current limiting resistor 7. At this time, the pressure switch contact connected to the instrument electrical signal interface 12 is connected to one side of the pressure switch contact through the positive power supply terminal 20 and two power supply diodes 10, and the other side of the contact is connected to the negative power supply 21 through the current limiting resistor 14 and the discharge resistor 17.

[0068] 2) Channel selection circuit:

[0069] The "channel selection" signal of the microcontroller is cleared, and the MOS tube 3 is reliably turned off under the action of the pull-down resistor 2 and the current limiting resistor 1. At this time, since analog signal acquisition is not required, there is no need to select the signal of the corresponding channel to output to the external standard device. The microcontroller determines the action of the pressure switch and outputs the corresponding prompt signal.

[0070] 3) Channel protection circuit:

[0071] The protection circuit at this time is used to detect the action signal of the pressure switch contact. When the pressure switch does not reach the action value, the protection signal output terminal 18 is pulled down to a voltage of 0 by the discharge resistor 17; when the pressure switch reaches the action value, the contact is closed, the two ends of the instrument electrical signal interface 12 are short-circuited, the voltage at the upper end of the current limiting resistor 14 is pulled to the power supply voltage, and the voltage regulator diode 15 is turned on, so that the voltage of the protection signal output terminal 18 is clamped to the voltage regulator value of the diode (such as 3.3V).

[0072] The microcontroller detects the voltage status of the protection signal output terminal of each channel in real time to determine whether the pressure switch is actuated. After identifying the action signal, it outputs the sound and light prompt signal of the corresponding channel to remind the operator.

[0073] At present, the conventional instrument calibration method is to calibrate the single instrument one by one through the calibrator. During each instrument calibration process, 5 pressure points are generally selected. The pressure stabilization and pressure maintenance time at each pressure point is relatively long. The pressure device needs to be adjusted repeatedly to stabilize the pressure at the selected pressure point. The average calibration time for each instrument is about 25 minutes, of which the total time for pressurization and pressure stabilization is 20 minutes, accounting for 80% of the total time. If this part of time can be shortened, the entire instrument calibration time will be greatly reduced.

[0074] Taking the calibration of four instruments at the same time as an example, one pressurization and voltage stabilization can serve four instruments at the same time. The average calibration time of each instrument is reduced to 1 / 4 of the original time. That is, the calibration time of a single instrument is shortened by 15 minutes.

[0075] Taking VVER reactor nuclear power units as an example, nuclear power plants are generally designed with four sequential process systems, that is, there are often four instruments with the same parameters appearing at the same time. According to preliminary statistics, there are about 3,000 such instruments in a single unit and 6,000 in a dual unit. During the installation period, if each instrument is calibrated once, it can save about 6,000*15=90,000 minutes=62.5 days. After the unit is in operation, there will also be regular instrument calibration activities to produce long-term and continuous time benefits.

[0076] Considering that instrument calibration requires at least two people to perform simultaneously, the labor cost savings can be calculated based on the unit price of labor.

Claims

1. A multi-channel instrument calibration device control circuit, characterized in that: It comprises instrument circuits arranged in parallel between power supply terminals, wherein each instrument circuit comprises a channel power supply diode (10) and an instrument connected in series in sequence, one end of the electrical signal output end is connected to the positive electrode of the power supply, and the other end is connected to the instrument through a channel selection switch circuit.

2. A multi-channel instrument calibration device control circuit as claimed in claim 1, characterized in that: The power supply terminals are a 24V power supply positive terminal (20) and a 24V power supply negative terminal (21); one end of the electric signal output end is connected to the 24V power supply positive terminal (20), and the other end is connected to the instrument through a channel selection switch.

3. A multi-channel instrument calibration device control circuit as claimed in claim 2, characterized in that: One end of the channel power supply diode (10) of the instrument circuit is connected to the positive terminal (20) of the 24V power supply, and the other end is connected to the instrument. The other end of the instrument is connected to the negative terminal (21) of the 24V power supply through the channel power supply protection circuit.

4. A multi-channel instrument calibration device control circuit as claimed in claim 3, characterized in that: The channel power supply protection circuit includes a channel power supply circuit and a channel protection circuit connected in parallel.

5. A multi-channel instrument calibration device control circuit as claimed in claim 4, characterized in that: The channel power supply circuit comprises a channel power supply current limiting resistor (11), one end of the channel power supply current limiting resistor (11) is connected to the instrument, and the other end is connected to the drain of the channel power supply MOS tube (9), the gate of the channel power supply MOS tube (9) is connected to the channel power supply signal input terminal (13) through the channel power supply signal current limiting resistor (7), the source of the channel power supply MOS tube (9) is connected to the negative terminal (21) of the 24V power supply, and the gate of the channel power supply MOS tube (9) is also connected to the negative terminal (21) of the 24V power supply through the channel power supply signal pull-down resistor (8).

6. A multi-channel instrument calibration device control circuit as claimed in claim 5, characterized in that: The channel protection circuit comprises a protection signal current limiting resistor (14), one end of the protection signal current limiting resistor (14) is connected to the instrument, the other end is connected to the voltage stabilizing filter circuit, and the protection signal current limiting resistor (14) is also connected to the protection signal output terminal (18).

7. A multi-channel instrument calibration device control circuit as claimed in claim 6, characterized in that: The voltage stabilizing and filtering circuit comprises a discharge resistor (17), a voltage stabilizing diode (15), and a filtering capacitor (16) connected in parallel, wherein the positive electrode of the voltage stabilizing diode (15) is connected to the negative electrode terminal (21) of a 24V power supply.

8. A multi-channel instrument calibration device control circuit as claimed in claim 7, characterized in that: The channel selection switch circuit comprises a channel selection switch power supply arranged between a 24V power supply positive terminal (20) and a 24V power supply negative terminal (21), and a channel selection relay contact (5-2) arranged in each instrument circuit.

9. A multi-channel instrument calibration device control circuit as claimed in claim 8, characterized in that: The channel selection switch power supply comprises a channel selection relay coil (5-1) and a channel selection MOS tube (3) connected in series, wherein the channel selection relay coil (5-1) corresponds to the channel selection relay contact (5-2) and controls the on and off of the channel selection relay contact (5-2), the channel selection relay coil (5-1) is connected to the drain of the channel selection MOS tube (3), the source of the channel selection MOS tube (3) is connected to the negative terminal (21) of a 24V power supply, the gate of the channel selection MOS tube (3) is connected to the negative terminal (21) of the 24V power supply through a channel selection signal pull-down resistor (2), and the gate of the channel selection MOS tube (3) is also connected to the channel selection signal current limiting resistor (1).

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