A circuit system and its application

Abstract

The present invention relates to a circuit system and a test device using the circuit system. The circuit system includes a circuit and an electrochemical sensor connected to the circuit, wherein the circuit includes a reference voltage circuit, a constant potential circuit and a micro-signal measurement circuit, and an on-off switch is arranged on the corresponding circuit. The circuit system and the test device of the present invention can significantly reduce the detection noise, improve the detection limit capability, and promote the application of electrochemical sensors in clinical sample detection.

Description

Technical Field

[0001] The present invention relates to the field of electricity, and in particular to a circuit system for detecting an analyte in a sample and an application thereof. Background Art

[0002] Electrochemical sensors have many advantages such as high efficiency, simplicity, sensitivity, speed, easy miniaturization, integration, and low energy consumption. In recent years, with the rapid development of related disciplines such as electrochemistry, materials science, and biology, electrochemical sensors have been widely used in the automotive industry, environmental monitoring, food safety, clinical diagnosis and other fields.

[0003] The working principle of electrochemical sensors is to place the substance to be tested in an electrochemical reaction cell in an appropriate form, measure the changes in its electrochemical parameters (such as potential, current, and conductivity), and determine the content of the substance to be tested. Electrochemical sensors can be divided into potentiometric sensors, amperometric sensors, and conductivity sensors according to their output signals.

[0004] Current-type electrochemical sensors are widely used, including some gas sensors such as carbon monoxide sensors, nitric oxide sensors, oxygen sensors, etc., and biosensors such as blood glucose test strips, blood ketone test strips, uric acid test strips, etc., which are all based on the principle of current-type sensors. The simplest form of this type of sensor is a two-electrode system, consisting of a working electrode (sensitive electrode) and a counter electrode, separated by a thin layer of electrolyte. When the sample to be tested enters the sensor, an oxidation or reduction reaction occurs on the surface of the working electrode, generating a current that flows through the two electrodes through an external circuit. The magnitude of the current generated is proportional to the concentration of the substance to be tested, and the external circuit infers the concentration of the substance to be tested by measuring the magnitude of the current.

[0005] In order for the reaction to occur, the potential of the working electrode needs to be kept within a specific range, so some electrochemical sensors need to maintain a bias voltage between the working electrode and the counter electrode. When the concentration of the reactant increases, the reaction current increases, and the potential of the counter electrode changes due to polarization, causing the potential of the working electrode to change accordingly. If the concentration of the reactant continues to increase, the potential of the working electrode may eventually exceed its allowable range, and the sensor signal will not be linear. Therefore, in response to the above problems, technicians introduced a reference electrode and applied a reference potential to the reference electrode using a constant potential circuit; during the detection process, there is basically no current flowing through the reference electrode, so a constant potential is maintained between the working electrode and the reference electrode; at this time, the counter electrode can still be polarized and form a reaction loop with the working electrode, but it will not limit the upper detection limit of the sensor.

[0006] Some electrochemical sensors, such as nitric oxide gas sensors (such as Alphasense's NO B4 nitric oxide sensor), will produce a relatively large, rapidly decreasing baseline signal after a new bias voltage is applied, and it takes a relatively long time to stabilize. Therefore, for such electrochemical sensors, manufacturers usually configure the bias voltage circuit on the sensor before the product leaves the factory, and power it with a battery to ensure that the sensor is "ready to work".

[0007] At present, electrochemical sensors are often used in the detection of trace substances, such as the detection of nitric oxide in exhaled breath. Because the content of the substance being measured is very low, the response signal of the electrochemical sensor is very small, so some weak interference (such as interference with the balance current of the electrode loop) will also cause significant noise interference to the detection signal of the working electrode. However, the existing technology has not yet effectively solved the problem of background noise (such as the background noise generated by the balance current of the electrode loop), and the accuracy, reliability and other performance of the electrochemical sensor detection results are subject to certain limitations, and even affect the application of its detection results. Summary of the invention

[0008] In order to overcome the above-mentioned problems and defects existing in the prior art, the present invention proposes a circuit system associated with an electrochemical sensor and a corresponding detection method, so as to eliminate the interference of factors such as the electrode loop balance current on the working electrode detection signal, reduce the background noise of the detection signal, and improve the precision of the detection result.

[0009] To achieve the purpose of the present invention, the present invention provides the following technical solutions.

[0010] The present invention provides a circuit system, comprising a circuit and an electrochemical sensor connected to the circuit, wherein a counter electrode on the electrochemical sensor is connected to the circuit via an on-off element, and the on-off element controls the connection or disconnection between the counter electrode and the circuit.

[0011] In one embodiment, the electrochemical sensor includes a working electrode, a counter electrode, a reference electrode, and an auxiliary electrode.

[0012] Furthermore, the circuit includes a reference voltage generating circuit, a constant potential circuit and a micro-signal measuring circuit. The reference voltage generating circuit is connected to the electrochemical sensor through the constant potential circuit. The working electrode and the auxiliary electrode of the electrochemical sensor are respectively connected to the micro-signal testing circuit.

[0013] Furthermore, the counter electrode and the reference electrode on the electrochemical sensor are connected to the constant potential circuit respectively. Furthermore, the on-off element is arranged between the counter electrode and the constant potential circuit.

[0014] In one embodiment, the circuit system further includes a differential circuit, and the working electrode and the auxiliary electrode are connected to the differential circuit via a micro-signal measurement circuit.

[0015] Furthermore, the on-off element is selected from an on-off switch, a relay, a field effect transistor, an analog switch or a triode.

[0016] The present invention provides a circuit system, including an electrochemical sensor and a circuit. The electrochemical sensor includes a working electrode, a counter electrode, a reference electrode and an auxiliary electrode. An on-off switch is provided on the circuit connected to the counter electrode, and the on-off switch controls the on-off between the counter electrode and the circuit.

[0017] Furthermore, the circuit includes a reference voltage generating circuit, a constant potential circuit and a micro-signal measuring circuit.

[0018] Furthermore, the on-off switch is arranged between the constant potential circuit and the counter electrode. The counter electrode is connected to the constant potential circuit through the on-off switch; the reference voltage generating circuit is connected to the reference electrode of the electrochemical sensor through the constant potential circuit, and the constant potential circuit is also connected to the counter electrode of the electrochemical sensor; the working electrode and the auxiliary electrode of the electrochemical sensor are respectively connected to the micro-signal test circuit to detect the signal generated by the reaction; the micro-signal measurement circuit and the constant potential circuit (and the reference voltage generating circuit) are all connected to the external circuit.

[0019] Furthermore, in addition to the aforementioned on-off switch, the element for controlling the on-off between the electrode and the circuit may also be a relay, a field effect transistor, an analog switch or a triode, as well as other on-off elements that can realize the on-off function.

[0020] The circuit of the circuit system may be an integrated reference voltage generating circuit, a constant potential circuit and a micro-signal measuring circuit, as well as an integrated circuit or chip having a switching function on the connection electrode.

[0021] The micro-signal measurement circuit is an I / V conversion amplifier circuit, through which the reaction current signals on the working electrode and the auxiliary electrode can be detected.

[0022] Furthermore, the circuit system may be provided with a differential circuit after the micro-signal measurement circuits of the working electrode and the auxiliary electrode, so as to directly detect the differential signal during detection.

[0023] The present invention provides a testing device for detecting an analyte in a sample, wherein the testing device comprises the circuit system of the present invention.

[0024] Furthermore, the sample is a gas sample.

[0025] Furthermore, the analyte is a trace substance with a very small content. For example, the trace substance is selected from nitric oxide in a gas sample. Furthermore, the gas sample is a breath sample.

[0026] Furthermore, the testing device also includes an air inlet, an air outlet and an air chamber, and the electrochemical sensor is installed in the air chamber.

[0027] The present invention provides a testing device for detecting nitric oxide, wherein the testing device comprises the circuit system of the present invention.

[0028] The present invention provides a detection method for reducing signal noise, the method comprising providing a testing device, the testing device comprising the circuit system of the present invention; during detection, the connection between the electrode and the circuit is disconnected.

[0029] Furthermore, before detection, the electrodes and the circuit are kept connected.

[0030] Furthermore, after the detection is completed, the connection between the electrode and the circuit is restored.

[0031] Specifically, the detection method includes the following steps: before detection, applying a bias voltage to the electrochemical sensor, at which time the electrode and the circuit remain connected; during detection, disconnecting the on-off element so that the electrode and the circuit are not connected; after the detection, reconnecting the on-off element so that the electrode and the circuit are connected.

[0032] Furthermore, before detection, a bias voltage is applied between the working electrode, the auxiliary electrode and the reference electrode of the electrochemical sensor to stabilize the baseline signal of the electrochemical sensor.

[0033] A detection method based on the circuit system of the present invention comprises the following steps: before detection, applying a bias voltage between electrodes, at which time the on-off switch remains connected to connect the electrodes to the circuit; during detection, disconnecting the on-off switch to disconnect the electrodes from the circuit; after the detection, reconnecting the on-off switch on the electrode circuit to prepare for the next detection.

[0034] Furthermore, before detection, the circuit applies bias voltage to the working electrode, auxiliary electrode and reference electrode of the electrochemical sensor in advance through the reference voltage generating circuit and constant potential circuit therein, and makes them reach balance and stability. At this time, the on-off switch on the circuit connected to the counter electrode remains connected. During detection, the on-off switch is turned off to disconnect the counter electrode from the constant potential circuit. At this time, due to the capacitance of the electrochemical sensor, the counter electrode and the reference electrode still maintain a potential close to that before disconnection, ensuring that the electrochemical sensor correctly completes the detection. After the detection is completed, the on-off switch is reconnected to connect the counter electrode to the constant potential circuit, and the constant potential circuit and the electrochemical sensor are rebalanced and stabilized to prepare for the next detection.

[0035] Based on the circuit system and detection method of the present invention, the present invention also provides the application of the circuit system and detection method in nitric oxide detection, including applying the circuit system to a nitric oxide electrochemical sensor, and completing the detection of nitric oxide by the detection method of the present invention. Furthermore, the circuit system is installed on a nitric oxide measuring device.

[0036] A detection method for detecting an analyte in a sample includes providing a test device, wherein the test device includes the circuit system described in the present invention, and the detection steps include: before detection, connecting the electrode and the circuit; during detection, disconnecting the connection between the electrode and the circuit, and the test device detects the analyte in the sample; after the detection, connecting the connection between the electrode and the circuit.

[0037] Furthermore, the sample is a gas sample. Furthermore, the analyte is a trace substance with a very small amount, for example, the trace substance is selected from nitric oxide in the gas sample.

[0038] Furthermore, the method includes the following steps: before detection, applying a bias voltage to the electrochemical sensor to keep the electrode and the circuit connected; during detection, disconnecting the on-off element to disconnect the electrode and the circuit; after the detection, reconnecting the on-off element to connect the electrode to the circuit.

[0039] Furthermore, during detection, a gas sample is input into the test device, the input gas contacts the electrochemical sensor, and the test device detects the content of nitric oxide in the gas sample.

[0040] By using the circuit system of the present invention, and the test device and detection method using the circuit system, an on-off element is set between the counter electrode and the circuit on the electrochemical sensor, and the on-off switch is switched between the connected and disconnected states, which can effectively eliminate the interference of factors such as the counter electrode loop balance current on the working electrode detection signal, reduce the background noise of the detection signal, improve the precision of the detection result, and significantly improve the detection performance of the electrochemical sensor. The circuit system of the present invention can be widely used in sample analysis, and can significantly improve the accuracy of detection, especially in the analysis of trace substances, such as the analysis of the content of nitric oxide in exhaled breath. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a circuit structure block diagram of an embodiment of the present invention, and the dotted frame is the circuit system described in the present invention in this embodiment.

[0042] Figure 2 The figure is a circuit diagram of an embodiment of the present invention.

[0043] Figure 3 This is an example of a circuit for generating a reference voltage and a bias voltage.

[0044] Figure 4 This is a curve chart of the comparative test results based on NO sensor - 0ppb (high purity nitrogen).

[0045] Figure 5 This is a curve diagram of the comparative test results based on the NO sensor - 20ppb NO standard gas.

[0046] Figure 6 This is a curve diagram of the comparative test results based on the NO sensor - 65ppb NO standard gas. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0048] like Figure 1 In one design scheme of the present invention shown, the electrochemical sensor includes a working electrode (WE), a counter electrode (CE), a reference electrode (RE) and an auxiliary electrode (AE); the counter electrode and the reference electrode are respectively connected to a constant potential circuit, and an on-off switch is provided between the counter electrode and the constant potential circuit; the reference voltage generating circuit is connected to the reference electrode of the electrochemical sensor through the constant potential circuit; the working electrode and the auxiliary electrode of the electrochemical sensor are respectively connected to a micro-signal test circuit to detect the signal generated by the reaction; the micro-signal measurement circuit and the constant potential circuit (as well as the reference voltage generating circuit) are both connected to an external circuit.

[0049] by Figure 2The figure is shown as an example to illustrate the circuit system designed for the electrochemical sensor with four electrodes according to the present invention.

[0050] like Figure 2 As shown, the electrochemical sensor includes four electrodes, namely, a counter electrode (C), a reference electrode (R), a working electrode (W), and an auxiliary electrode (A). The auxiliary electrode (A) is used to eliminate the influence of the working environment (such as temperature) on the baseline current. The operational amplifier (U2A) keeps the potential of the reference electrode (R) equal to the input reference potential Vref, and outputs a suitable potential to the counter electrode (C). An on-off switch (K1) is connected to the counter electrode to control the on-off between the counter electrode and the circuit; the operational amplifier (U3A) applies a potential Vbias to the working electrode (W) of the electrochemical sensor through the input terminal 3 to maintain the bias voltage between the working electrode (W) and the reference electrode (R). At the same time, the operational amplifier (U3A), the resistor R9, and the capacitor C3 form a micro-signal measurement circuit for I / V conversion. At the input of the operational amplifier (U3A), the resistor R9 and the capacitor C3 form a micro-signal measurement circuit for I / V conversion. The output terminal 1 outputs a signal to detect the micro-signal generated on the working electrode (W) during the reaction; the working mode of the auxiliary electrode (A) is consistent with that of the working electrode (W), and the operational amplifier (U4A) applies a potential Vbias to the auxiliary electrode (A) of the electrochemical sensor through the input terminal 3 to maintain the bias voltage between the auxiliary electrode (A) and the reference electrode (R). At the same time, the operational amplifier (U4A), the resistor R11, and the capacitor C4 form an I / V conversion micro-signal measurement circuit, and the output terminal 1 of the operational amplifier (U4A) outputs a signal to detect the micro-signal generated on the auxiliary electrode (A) during the reaction. In this example, a differential circuit (circuit in the dotted box) is provided after the micro-signal measurement circuit of the working electrode and the auxiliary electrode, and the differential signal is directly detected during detection, that is, the signal generated during the detection of the working electrode (W) and the auxiliary electrode (A) is processed by the differential amplifier U5, and the final signal Vout is output to eliminate the influence of the working environment (such as temperature) on the reaction baseline current.

[0051] Figure 3 is an example of a circuit for generating a reference voltage and a bias voltage, and the circuit for generating a reference voltage and a bias voltage may also adopt other suitable methods. Figure 3 In the example shown, U1 is a reference voltage source, and outputs Vref and Vbias, which are connected to input terminals 3 of the corresponding operational amplifier (U2A) and input terminals 3 of the operational amplifiers (U3A, U4A), respectively.

[0052] Test Example 1 Test comparison of two circuit systems

[0053] based on Figure 2 The circuit system adopts a four-electrode nitric oxide (NO) electrochemical gas sensor (referred to as NO sensor) to carry out the detection effect test of the present invention.

[0054] The measurement method is as follows: a nitric oxide (NO) electrochemical gas sensor and a circuit are installed in a measuring device, which is provided with an air inlet and an air outlet, and then the gas to be measured is pumped into the air inlet through an air pump for measurement.

[0055] For the embodiments of the present invention, the test process of the detection method is as follows:

[0056] 1) Before detection, apply a bias voltage to the electrochemical sensor in advance (for example, the bias voltage is set to 0.35V: specifically, 0.90V for the reference electrode, 1.25V for the working electrode and the auxiliary electrode, for at least 24 hours to stabilize the baseline signal of the electrochemical sensor;

[0057] 2) At the beginning of the test, disconnect the on-off switch K1 on the counter electrode, test the baseline signal for 8 seconds, and collect 1 data every 0.1 seconds.

[0058] 3) Then, a nitric oxide sample gas (balanced with nitrogen) is passed through the gas chamber of the electrochemical sensor at a constant flow rate (1 mL / s), and the detection signal is tested for 22 seconds, with one data point collected every 0.1 seconds;

[0059] 4) After the test is completed, stop ventilation and data sampling, and immediately connect the on-off switch K1 on the electrode to restore the electrochemical sensor to balance in preparation for the next test.

[0060] The circuit system used as a control (control example) is basically the same Figure 2 The same, except that the on-off switch K1 is not connected to the counter electrode, but the counter electrode is directly connected to the constant potential circuit, and the counter electrode remains connected. The test process of the detection method as a control example is as follows:

[0061] 1) Before detection, apply a bias voltage to the electrochemical sensor (for example, the bias voltage is set to 0.35V: specifically, 0.90V for the reference electrode, and 1.25V for the working electrode and the auxiliary electrode) for at least 24 hours to stabilize the baseline signal of the electrochemical sensor;

[0062] 2) At the beginning of the test, the test baseline is 8 seconds, and 1 data is collected every 0.1 seconds;

[0063] 3) Then, nitric oxide gas (balanced with nitrogen) was passed through the gas chamber of the electrochemical sensor at a constant flow rate (1 mL / s), and the detection signal was tested for 22 seconds, with one data point collected every 0.1 seconds;

[0064] 4) After the test is completed, stop ventilation and data sampling.

[0065] The test tested three concentrations of nitric oxide gas, namely 0 ppb (high purity nitrogen), 20 ppb, and 65 ppb. For each concentration of gas, the embodiment of the present invention and the prior art were tested three times respectively. The test result curve of the comparison test is shown in FIG. Figures 4 to 6 As can be seen from the figure, the curve of the test result of the control example fluctuates significantly and has a large amount of visible noise, while the curve of the test result of the present invention is very smooth and has very little noise.

[0066] The test results of the reaction plateau period from 25.1 seconds to 30.0 seconds (starting from the baseline measurement) were used to calculate the mean, standard deviation and coefficient of variation of the results within each test; then the total mean, standard deviation and coefficient of variation between the three measurements of each concentration of gas for each technology were calculated. The results of the technology of the present invention and the prior art were compared, and the data are shown in Tables 1 to 3.

[0067] Table 1. Comparison of test results – 0ppb (high purity nitrogen)

[0068]

[0069] Table 2. Comparison of test results – 20ppb

[0070]

[0071] Table 3. Comparison of test results – 65ppb

[0072]

[0073] As shown in Table 1, the standard deviation SD within the prior art test is 4.17-6.13 ppb, and the standard deviation SD between tests is 0.53 ppb; while the standard deviation SD within the test of the present invention is only 0.07-0.10 ppb, and the standard deviation SD between tests is only 0.17 ppb. It can be seen that compared with the prior art, the present invention reduces the signal noise by dozens of times, greatly improves the signal-to-noise ratio, and greatly improves the ability to detect the lower limit of nitric oxide; at the same time, the present invention also significantly improves the repeatability performance between tests.

[0074] As shown in Table 2, the coefficient of variation CV within the prior art test is 27.9% to 33.8%, and the coefficient of variation CV between tests is 18.1%; while the coefficient of variation CV within the test of the present invention is only 0.5% to 0.9%, and the coefficient of variation CV between tests is only 1.2%. As shown in Table 3, the coefficient of variation CV within the prior art test is 4.8% to 8.2%, and the coefficient of variation CV between tests is 2.5%; while the coefficient of variation CV within the test of the present invention is only 0.3%, and the coefficient of variation CV between tests is only 0.2%. It can be seen that compared with the prior art, the signal noise of the present invention is significantly reduced, the signal-to-noise ratio is greatly improved, and the repeatability performance between tests is also significantly improved.

[0075] Test Example 2

[0076] This embodiment uses a multimeter to monitor the potential before the test (before the test, the on-off switch of the electrode remains connected), during the test (the electrode is disconnected by the on-off switch during the test), and after the test (after the test, the on-off switch of the electrode is immediately restored to connection) of the test technology of the present invention, and records the potential values ​​before the test, at the end of the test, and after the test. Three concentrations of nitric oxide standard gas, 35ppb, 210ppb, and 3330ppb, were tested respectively, and each concentration was tested twice, and the results are shown in Table 4.

[0077] Monitoring found that: before the test, the potential of the electrode was basically stable (fluctuation of about 0.1mV); after the test started, the on-off switch of the electrode was disconnected, and the potential of the electrode gradually rose slightly, with a small increase at low concentrations and a slightly larger increase at high concentrations, but the increase was not large; after the test, the on-off switch of the electrode was immediately connected, and the potential of the electrode immediately returned to the level before the test, with an interval of no more than 1 second. It can be seen that due to the high capacitance of the electrochemical sensor, after the electrode was disconnected during the test, within the measurement range of nitric oxide as high as 3330ppb (the upper limit of the test of FeNO detection products on the market), its potential change was very small and would not affect the test; after the test, the connection of the electrode was restored, and the potential of the electrode recovered rapidly (within 1 second), which did not affect the actual use of the product.

[0078] Table 4 Monitoring data of electrode potential during the test of the present invention (unit: mV)

[0079] NO concentration test Before testing End of test rise 1 second after detection 35ppb Test 1 887.7 888.5 0.8 887.7 35ppb Test 2 887.7 888.4 0.7 887.8 210ppb Test 1 887.9 888.9 1.0 887.9 210ppb Test 2 887.9 888.9 1.0 888.0 3330ppb Test 1 888.1 892.9 4.8 887.9 3330ppb Test 2 887.1* 891.5 4.4 887.2

[0080] *: The instrument was restarted during this test, and the previous 5 results were continuous tests.

[0081] Therefore, the results show that: compared with the prior art, the technology of the present invention significantly reduces the signal noise of the electrochemical sensor, greatly improves the signal-to-noise ratio, the signal curve within the test is more stable, and the signal curve between tests is more consistent. It can be seen that the technology of the present invention provides a technical basis for improving the detection limit capability of the electrochemical sensor and shortening the detection time; the technology of the present invention has great application value for the detection of some trace substances by electrochemical sensors. For example, in the detection of exhaled nitric oxide, the concentration of exhaled nitric oxide in human body is usually between a few ppb and tens of ppb. The clinical critical point of FeNO50 for normal people and patients is 25ppb, and the clinical critical point of CaNO is only 5ppb. Therefore, the test precision and accuracy of low-concentration NO are very important for the clinical application of the test results. The technology of the present invention significantly reduces the detection noise, improves the detection limit capability, improves the detection repeatability, and reduces the difference between tests (especially at low concentrations), which is of great significance for the application of electrochemical sensors in clinical detection.

[0082] The above embodiments are merely descriptions of some preferred implementations of the present invention. Any changes or substitutions that can be easily conceived by persons familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention.

Claims

1. A circuit system for measuring the reaction current of an electrochemical sensor, comprising a circuit and an electrochemical sensor connected to the circuit, characterized in that: The electrochemical sensor includes a working electrode, a counter electrode, a reference electrode and an auxiliary electrode, and the circuit includes a constant potential circuit and a micro-signal measurement circuit; the working electrode and the auxiliary electrode of the electrochemical sensor are respectively connected to the micro-signal test circuit to measure the current generated when the electrochemical sensor reacts; the counter electrode and the reference electrode on the electrochemical sensor are respectively connected to the constant potential circuit; the on-off element is arranged between the counter electrode and the constant potential circuit, and the on-off element controls the connection or disconnection between the counter electrode and the circuit. When not detecting, the counter electrode and the circuit remain connected, and when detecting, the connection between the counter electrode and the circuit is disconnected.

2. The circuit system according to claim 1, characterized in that: The circuit also includes a reference voltage generating circuit, which is connected to the reference electrode of the electrochemical sensor through a constant potential circuit.

3. The circuit system according to claim 1, characterized in that: A differential circuit is also provided, and the working electrode and the auxiliary electrode are connected to the differential circuit via a micro-signal measuring circuit.

4. The circuit system according to claim 1, characterized in that: The on-off element is selected from an on-off switch, a relay, a field effect transistor, an analog switch or a triode.

5. The circuit system according to claim 1, characterized in that: The micro-signal measurement circuit is an I / V conversion circuit, and the reaction current signal on the working electrode is detected by the micro-signal measurement circuit.

6. The circuit system according to claim 1, characterized in that: Before detection, the electrodes and the circuit remain connected and a bias voltage is applied to the electrochemical sensor.

7. The circuit system according to claim 6, characterized in that: Before detection, the electrode and the circuit remain connected. The circuit applies a bias voltage to the working electrode, auxiliary electrode and reference electrode of the electrochemical sensor through the reference voltage generating circuit and constant potential circuit therein, so that the baseline signal of the electrochemical sensor is stabilized.

8. The circuit system according to any one of claims 1 to 7, characterized in that The electrochemical sensor is an electrochemical sensor for detecting gas.

9. The circuit system according to claim 8, characterized in that: The electrochemical sensor is an electrochemical sensor for analyzing the content of nitric oxide in exhaled air.

10. A test device for detecting an analyte in a sample, characterized in that: The testing device comprises the circuit system according to any one of claims 1 to 9.

11. The testing device according to claim 10, characterized in that: The analyte is a gas.

12. The testing device according to claim 11, characterized in that: The analyte is nitric oxide in exhaled breath.

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