Measuring circuit

Abstract

The invention discloses a measuring circuit. The measuring circuit comprises a main measuring circuit and a redundant measuring circuit. The main circuit comprises a first operational amplifier, a first excitation signal source and a first phase-sensitive detector; the redundant circuit is composed of a second operational amplifier, a second excitation signal source and a second phase-sensitive detector. Excitation signal frequencies are different, signal interference is avoided, and distinguishing is convenient. When the main circuit is normal, the first operational amplifier adjusts the output voltage of the temperature sensor to a first amplified voltage, the first excitation signal source outputs a first reference voltage, and the first phase sensitive detector processes the first amplified voltage and the first reference voltage to generate a first output voltage. And after the main circuit fails, the redundant circuit automatically takes over and outputs a second voltage to ensure continuous operation of the system. According to the design, continuous and stable operation of the system is ensured, shutdown or abnormal operation is avoided, and the overall reliability is remarkably improved.

Description

Technical Field

[0001] The present application relates to the field of electronic measurement technology, and in particular to a measurement circuit. Background Art

[0002] The PT100 temperature sensor is a sensor whose resistance value changes with temperature. It has the characteristics of high precision, reliability, mechanical strength and long life, and is widely used in meteorology, agriculture, chemical fiber, food, automobiles, home appliances, industrial automation and experimental instruments. However, if the PT100 measurement circuit fails (such as damage to the operational amplifier, signal source or sensor), the temperature measurement will not be able to continue, which may cause the system to shut down or operate abnormally. Summary of the invention

[0003] Based on the above problems, the present application provides a measurement circuit that can ensure that the system can continue to perform temperature measurement when the temperature sensor measurement circuit fails, thereby avoiding shutdown or abnormal operation.

[0004] The embodiments of the present application disclose the following technical solutions:

[0005] A measurement circuit, the measurement circuit comprising: a main measurement circuit and a redundant measurement circuit;

[0006] The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector; the redundant measurement circuit includes a second operational amplifier, a second excitation signal source and a second phase-sensitive detector; the first excitation signal and the second excitation signal have different frequencies;

[0007] The first operational amplifier is respectively connected to the positive port and the negative port of the temperature sensor; the first phase-sensitive detector is respectively connected to the first operational amplifier and the first excitation signal source; the second operational amplifier is respectively connected to the positive port and the negative port of the temperature sensor; the second phase-sensitive detector is respectively connected to the second operational amplifier and the second excitation signal source; when the main measurement circuit is not faulty, the temperature sensor is measured by the main measurement circuit to obtain the output voltage; when the main measurement circuit is faulty, the temperature sensor is measured by the redundant measurement circuit to obtain the output voltage;

[0008] The first operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a first amplified voltage;

[0009] The first excitation signal source is used to output a first reference voltage;

[0010] The first phase-sensitive detector is used to perform signal processing on the first amplified voltage and the first reference voltage to obtain a first output voltage;

[0011] The second operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a second amplified voltage;

[0012] The second excitation signal source is used to output a second reference voltage;

[0013] The second phase-sensitive detector is used to perform signal processing on the second amplified voltage and the second reference voltage to obtain a second output voltage.

[0014] In a possible implementation, the first phase-sensitive detector includes a first multiplier and a first filter;

[0015] The first multiplier is used for multiplying the first amplified voltage and the first reference voltage to obtain a first product voltage;

[0016] The first filter is used to filter the first product voltage to obtain the first output voltage.

[0017] In a possible implementation, the second phase-sensitive detector includes a second multiplier and a second filter;

[0018] The second multiplier is used for multiplying the second amplified voltage and the second reference voltage to obtain a second product voltage;

[0019] The first filter is used to filter the second product voltage to obtain the second output voltage.

[0020] In a possible implementation, the main measurement circuit further includes: a first converter; the first converter is connected to the first excitation signal source and the positive port of the temperature sensor respectively;

[0021] The first converter is used to convert the first reference voltage output by the first excitation signal source into a first reference current to provide an operating current for the temperature sensor.

[0022] In a possible implementation, the redundant measurement circuit further includes: a second converter; the second converter is connected to the second excitation signal source and the positive port of the temperature sensor respectively;

[0023] The second converter is used to convert the second reference voltage output by the second excitation signal source into a second reference current to provide an operating current for the temperature sensor.

[0024] In a possible implementation manner, the frequency of the first excitation signal is 1.7 kHz or 17.7 kHz.

[0025] In a possible implementation manner, the frequency of the second excitation signal is 1.7 kHz or 17.7 kHz.

[0026] Compared with the prior art, this application has the following beneficial effects:

[0027] The present application provides a measurement circuit. Specifically, the measurement circuit includes a main measurement circuit and a redundant measurement circuit. The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector, and the redundant measurement circuit is composed of a second operational amplifier, a second excitation signal source and a second phase-sensitive detector. The excitation signal frequencies of the two are different to avoid mutual interference and facilitate the distinction between the two signals. When the main measurement circuit is normal, the first operational amplifier adjusts the output voltage of the temperature sensor to obtain a first amplified voltage, and the first excitation signal source outputs a first reference voltage, so that the first phase-sensitive detector performs signal processing on the first amplified voltage and the first reference voltage to obtain a first output voltage. Once the main circuit fails, the redundant measurement circuit automatically takes over, and the second operational amplifier, the second excitation signal source and the second phase-sensitive detector output the second output voltage. The measurement circuit of the present application is respectively provided with a main measurement circuit and a redundant measurement circuit. When the main measurement circuit fails, it can automatically switch to the redundant circuit to continue temperature measurement, avoiding system shutdown or abnormal operation due to failure, and significantly improving the reliability of the overall system. At the same time, the complementary effect of the main measurement circuit and the redundant measurement circuit can switch to the redundant circuit for measurement in time when the main circuit fails, thereby greatly reducing the risk of interruption or inaccurate measurement data due to circuit failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A structural diagram of a measurement circuit provided in an embodiment of the present application;

[0030] Figure 2 A structural diagram of another measurement circuit provided in an embodiment of the present application;

[0031] Figure 3 A structural diagram of another measurement circuit provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of the internal circuit of a PT100 temperature sensor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] To facilitate understanding of the technical solutions provided by the embodiments of the present application, the background technology involved in the embodiments of the present application will be described below.

[0034] PT100 temperature sensor is a temperature sensor whose resistance value changes with temperature. It has the characteristics of high measurement accuracy, reliable and stable performance, high mechanical strength and long product life. These characteristics make PT100 widely used in various fields, including meteorology, agriculture and forestry, chemical fiber, food, automobile, household appliances, industrial automation measurement and various experimental instruments. Due to its high accuracy and stability, PT100 has become the preferred temperature measurement device in many industries.

[0035] However, the measurement circuit of this temperature sensor does not have the ability of redundant measurement. This means that when the measurement circuit is abnormal or fails (for example, the operational amplifier, signal source or sensor itself is damaged), the temperature measurement will not be able to continue. Once the main measurement circuit fails, the entire system may shut down or fail to operate normally, thereby increasing the risk of system failure.

[0036] In the above description, "system" refers to any equipment or device that relies on PT100 temperature sensors for temperature monitoring and control. These systems can be diverse, including but not limited to the following categories:

[0037] Industrial automation systems: such as temperature control equipment on production lines, ensuring that the temperature during the process remains within the set range.

[0038] Meteorological monitoring system: used for environmental temperature monitoring and providing accurate meteorological data.

[0039] Agriculture and forestry monitoring systems: For example, greenhouse control systems ensure suitable temperature conditions for crop growth.

[0040] Food processing systems: such as baking equipment, freezing equipment, etc., to ensure temperature control during food processing.

[0041] Automotive systems: such as engine cooling systems, which ensure that the engine operates within a safe operating temperature range.

[0042] Household appliances: such as air conditioners, refrigerators, etc., to ensure the comfort of the home environment and the safety of food preservation.

[0043] Experimental instruments and equipment: such as temperature control equipment in the laboratory, to ensure the accuracy and reliability of experimental data.

[0044] These systems are highly dependent on the accurate temperature measurement provided by the PT100 temperature sensor. Once the main measurement circuit fails, the system will lose the ability to monitor the temperature, which may cause equipment overheating, control system failure or other serious consequences, thus affecting the normal operation and safety of the system.

[0045] In order to solve this problem, a measurement circuit is provided in an embodiment of the present application, and the measurement circuit includes a main measurement circuit and a redundant measurement circuit. The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector; the redundant measurement circuit includes a second operational amplifier, a second excitation signal source and a second phase-sensitive detector. The frequencies of the first excitation signal and the second excitation signal are different. Specifically: the first operational amplifier in the main measurement circuit is respectively connected to the positive port and the negative port of the temperature sensor, and the output voltage of the temperature sensor can be adjusted to obtain a first amplified voltage. The first excitation signal source outputs a first reference voltage, and the first phase-sensitive detector performs signal processing on the first amplified voltage and the first reference voltage to obtain a first output voltage. The second operational amplifier in the redundant measurement circuit is also connected to the positive port and the negative port of the temperature sensor, and the output voltage of the temperature sensor can be adjusted to obtain a second amplified voltage. The second excitation signal source outputs a second reference voltage, and the second phase-sensitive detector performs signal processing on the second amplified voltage and the second reference voltage to obtain a second output voltage. The measurement circuit of the present application includes a main measurement circuit and a redundant measurement circuit, which can automatically switch to the redundant circuit to continue temperature measurement when the main circuit fails, ensuring that the system will not shut down or operate abnormally due to a fault, thereby significantly improving the reliability of the system. The complementary effect of the main circuit and the redundant circuit ensures that when a fault occurs, the redundant circuit can take over the measurement task in time, reducing the risk of interruption or inaccurate measurement data due to circuit failure.

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] See also Figure 1 , Figure 1 This is a structural diagram of a measurement circuit provided in an embodiment of the present application. Figure 1 The measurement circuit shown includes a main measurement circuit and a redundant measurement circuit.

[0048] The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector; the redundant measurement circuit includes a second operational amplifier, a second excitation signal source and a second phase-sensitive detector; the first excitation signal and the second excitation signal have different frequencies;

[0049] The first operational amplifier is respectively connected to the positive port (such as Figure 1 UA in) and negative ports (such as Figure 1 The first phase-sensitive detector is connected to the first operational amplifier and the first excitation signal source respectively. The second operational amplifier is connected to the positive port and the negative port of the temperature sensor respectively. The second phase-sensitive detector is connected to the second operational amplifier and the second excitation signal source respectively. When the main measurement circuit is not faulty, the output voltage of the temperature sensor is measured by the main measurement circuit. When the main measurement circuit fails, the output voltage of the temperature sensor is measured by the redundant measurement circuit.

[0050] The first operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a first amplified voltage.

[0051] The first excitation signal source is used to output a first reference voltage.

[0052] The first phase-sensitive detector is used to perform signal processing on the first amplified voltage and the first reference voltage to obtain a first output voltage.

[0053] The second operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a second amplified voltage.

[0054] The second excitation signal source is used to output a second reference voltage.

[0055] The second phase-sensitive detector is used to perform signal processing on the second amplified voltage and the second reference voltage to obtain a second output voltage.

[0056] In a possible implementation manner, the frequency of the first excitation signal is 1.7 kHz (kilohertz) or 17.7 kHz.

[0057] In a possible implementation manner, the frequency of the second excitation signal is 1.7 kHz or 17.7 kHz.

[0058] See also Figure 2 , Figure 2 This is a structural diagram of another measurement circuit provided in an embodiment of the present application. Figure 2 As shown, the first phase-sensitive detector includes a first multiplier and a first filter. The second phase-sensitive detector includes a second multiplier and a second filter.

[0059] The first multiplier is used for multiplying the first amplified voltage and the first reference voltage to obtain a first product voltage.

[0060] The first filter is used to filter the first product voltage to obtain the first output voltage.

[0061] The second multiplier is used for multiplying the second amplified voltage and the second reference voltage to obtain a second product voltage.

[0062] The first filter is used to filter the second product voltage to obtain the second output voltage.

[0063] See also Figure 3 , Figure 3 This is a structural diagram of another measurement circuit provided in an embodiment of the present application. Figure 3 As shown, the main measurement circuit further includes: a first converter, the first converter is connected to the first excitation signal source and the positive port of the temperature sensor respectively. The redundant measurement circuit further includes: a second converter, the second converter is connected to the second excitation signal source and the positive port of the temperature sensor respectively.

[0064] The first converter is used to convert the first reference voltage output by the first excitation signal source into a first reference current to provide an operating current for the temperature sensor.

[0065] The second converter is used to convert the second reference voltage output by the second excitation signal source into a second reference current to provide an operating current for the temperature sensor.

[0066] In a possible implementation, the temperature sensor may be, but is not limited to, a PT100 temperature sensor. The present application does not impose any specific restrictions on the selection of the temperature sensor. When the temperature sensor is modified to another type of temperature sensor, it can also be detected by the measurement circuit disclosed in the present application. The subsequent description is illustrated by using a PT100 temperature sensor.

[0067] See also Figure 4 , Figure 4 A schematic diagram of the internal circuit of a PT100 temperature sensor provided in an embodiment of the present application. Figure 4 The PT100 temperature sensor is a three-wire PT100 temperature sensor, r is the lead resistance of the temperature sensor, R z is the zero point resistance of the temperature sensor, R ρ is the self-resistance of the temperature sensor, U A and U BIs the output voltage of the temperature sensor, GND is ground, and Is is a constant current power supply of 1mA (milliampere).

[0068] In one possible implementation, the operational amplifier predicts the output amplified voltage to be:

[0069] U S ( t ) = ( 2×U B -U A ) ×k=(R ρ -R Z )×I S (t);

[0070] Among them, the impedance in the line is small, α≈0. Considering the power frequency interference and other noise in the line, the actual amplified voltage u S( t ) For: s( t ) =U s cos(ωt+α)+U 50Hz cos(100πt+β)+u n , U s cos(ωt+α) is the amplified voltage predicted by the operational amplifier output, U 50Hz cos(100πt+β) is the interference signal, u n The interference signal refers to the interference generated by the power frequency signal. Usually, the power frequency signal is 50 Hz (Hertz). This application takes 50 Hz as an example for explanation. In practice, the expression of the interference signal can be adjusted according to the frequency of the power frequency signal.

[0071] Therefore, the multiplier multiplies the amplified voltage and the reference voltage of the excitation signal source to obtain the product voltage: U s ( t ) ×U r ( t ) =(U s cos(ωt+α)+U 50Hz cos(100πt+β)+u n )×

[0072] U r cos(ωt).

[0073] The product voltage is transformed into:

[0074]

[0075] in, It is related to the interference signal. In this expression, ω=2×π×17.7K, which turns the 50Hz power frequency interference into a high-frequency interference close to 17.7kHz. Converting the low-frequency power frequency interference into high-frequency interference makes it easier to remove the power frequency interference signal, so it can be filtered out by using a low-pass filter with a higher cut-off frequency. When the power frequency is other than 50Hz, it is similar. The same voltage is converted into the fifth voltage after passing through the multiplier, and the power frequency interference signal is converted into high-frequency interference.

[0076] After filtering by the filter in the phase-sensitive detector, the output voltage of the phase-sensitive detector is: The phase-sensitive detector mainly works on the principle of phase-locked amplification. Phase-locked amplification is a method of phase-sensitive detection of alternating signals. It uses a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, and only responds to the measured signal itself and those noise components with the same frequency (or multiple frequency) and phase as the reference signal. Therefore, it can greatly suppress useless noise and interference and improve the detection signal-to-noise ratio. The excitation signal in this embodiment is used as a reference signal. That is, the final output signal is only related to the signal output by the measured sensor and the excitation signal through the phase-sensitive detector.

[0077] The present application provides a measurement circuit, which adopts a combination of a main measurement circuit and a redundant measurement circuit to ensure that when the main measurement circuit fails, the redundant circuit can take over the work and ensure the stability and reliability of the measurement system. The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector, and the redundant measurement circuit uses a second operational amplifier, a second excitation signal source and a second phase-sensitive detector. The excitation signal frequencies of the main circuit and the redundant circuit are different, which helps to avoid interference and makes the two circuits easy to distinguish. When the main measurement circuit works normally, the signal of the temperature sensor is amplified by the first operational amplifier, and the reference voltage is provided by the first excitation signal source, and the output voltage is output after being processed by the first phase-sensitive detector. When the main circuit fails, the redundant circuit automatically switches to take over, and can still output the voltage through the second operational amplifier, the second excitation signal source and the second phase-sensitive detector. The measurement circuit of the present application includes a main measurement circuit and a redundant measurement circuit. When the main measurement circuit fails, the system can automatically switch to the redundant circuit to continue temperature measurement, thereby avoiding the system from shutting down or abnormal operation due to failure, and significantly improving the reliability of the overall system. The complementary effect of the main measurement circuit and the redundant measurement circuit ensures timely switching to the redundant circuit for measurement when the main circuit fails, greatly reducing the risk of interruption or inaccurate measurement data due to circuit failure.

[0078] The above is a detailed introduction to a measurement circuit provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0079] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0080] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A measuring circuit, characterized in that: The measuring circuit comprises: a main measuring circuit and a redundant measuring circuit; The main measurement circuit includes a first operational amplifier, a first excitation signal source and a first phase-sensitive detector; the redundant measurement circuit includes a second operational amplifier, a second excitation signal source and a second phase-sensitive detector; the first excitation signal and the second excitation signal have different frequencies; The first operational amplifier is respectively connected to the positive port and the negative port of the temperature sensor; the first phase-sensitive detector is respectively connected to the first operational amplifier and the first excitation signal source; the second operational amplifier is respectively connected to the positive port and the negative port of the temperature sensor; the second phase-sensitive detector is respectively connected to the second operational amplifier and the second excitation signal source; when the main measurement circuit is not faulty, the temperature sensor is measured by the main measurement circuit to obtain the output voltage; when the main measurement circuit is faulty, the temperature sensor is measured by the redundant measurement circuit to obtain the output voltage; The first operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a first amplified voltage; The first excitation signal source is used to output a first reference voltage; The first phase-sensitive detector is used to perform signal processing on the first amplified voltage and the first reference voltage to obtain a first output voltage; The second operational amplifier is used to adjust the output voltage of the temperature sensor to obtain a second amplified voltage; The second excitation signal source is used to output a second reference voltage; The second phase-sensitive detector is used to perform signal processing on the second amplified voltage and the second reference voltage to obtain a second output voltage.

2. The circuit according to claim 1, characterized in that The first phase-sensitive detector includes a first multiplier and a first filter; The first multiplier is used for multiplying the first amplified voltage and the first reference voltage to obtain a first product voltage; The first filter is used to filter the first product voltage to obtain the first output voltage.

3. The circuit according to claim 1, characterized in that The second phase-sensitive detector includes a second multiplier and a second filter; The second multiplier is used for multiplying the second amplified voltage and the second reference voltage to obtain a second product voltage; The first filter is used to filter the second product voltage to obtain the second output voltage.

4. The circuit according to claim 1, characterized in that The main measurement circuit further includes: a first converter; the first converter is connected to the first excitation signal source and the positive port of the temperature sensor respectively; The first converter is used to convert the first reference voltage output by the first excitation signal source into a first reference current to provide an operating current for the temperature sensor.

5. The circuit according to claim 1, characterized in that The redundant measurement circuit further includes: a second converter; the second converter is connected to the second excitation signal source and the positive port of the temperature sensor respectively; The second converter is used to convert the second reference voltage output by the second excitation signal source into a second reference current to provide an operating current for the temperature sensor.

6. The circuit according to claim 1, characterized in that The frequency of the first excitation signal is 1.7 kHz or 17.7 kHz.

7. The circuit according to claim 1, characterized in that The frequency of the second excitation signal is 1.7 kHz or 17.7 kHz.

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