Negative temperature coefficient (NTC) thermistor resistance value detection circuit

Abstract

The utility model discloses an NTC (Negative Temperature Coefficient) thermistor resistance value detection circuit, which belongs to the technical field of data acquisition and comprises a fixed value resistor I, a fixed value resistor II, an NTC thermistor, a switch module, a power supply module and a control module. The first fixed-value resistor and the NTC thermistor are connected in series to form a first test circuit, and the second fixed-value resistor and the NTC thermistor are connected in series to form a second test circuit. The power supply module and the control module are electrically connected with the switch module, the switch module executes on-off actions under the control action of the control module, and the output voltage of the power supply module is loaded to the test circuit I or the test circuit II. And one end of the NTC thermistor connected with the fixed-value resistor I and the fixed-value resistor II is electrically connected with the signal acquisition end of the control module, and the other end of the NTC thermistor is grounded. According to the utility model, the resistance value of the NTC thermistor can be measured without measuring the total voltage v of the measuring circuit, so that the problem of large detection error caused by the fact that the NTC resistance value is calculated by adopting the total voltage v of the circuit in the conventional NTC resistance value detection circuit is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of data acquisition, and particularly relates to an NTC thermistor resistance detection circuit. Background Art

[0002] An NTC thermistor is an oxide semiconductor ceramic composed of manganese (Mn), nickel (Ni), and cobalt (Co). Due to the characteristic that the resistance value of the NTC thermistor decreases as the temperature increases, it is often used as a thermometer and a temperature sensing device.

[0003] As Figure 1 shown, the current resistance detection circuit for the NTC thermistor is usually: a 10KΩ resistor is connected in series, and then the ADC is used to collect the voltage across the NTC thermistor, and then the current resistance value of the thermistor is calculated. Among them, v is the voltage loaded on the entire circuit, r is the current resistance value of the NTC thermistor, v1 is the voltage across the NTC thermistor, and according to the formula U = IR and v = ((v - v1) / 10000)*r, it is deduced that: r = 10000*v / (v - v1).

[0004] It can be seen that calculating r requires knowing the values of v and v1. v1 can be collected by the ADC, and v is obtained through the peripheral circuit (DC-DC step-down device). Due to the problem of device consistency in the peripheral circuit (such as the error of the resistance value of the resistor), there will be a certain deviation in the voltage v obtained by each device through the hardware circuit. However, when writing software, v usually takes a fixed value, resulting in a large error between the finally calculated r and the actual resistance value of the NTC thermistor. Content of the Utility Model

[0005] The utility model provides an NTC thermistor resistance detection circuit, which does not need to measure the total voltage v of the measurement circuit and can also measure the resistance value of the NTC thermistor, so as to solve the problem of large detection error caused by calculating the NTC resistance value using the total voltage v of the circuit in the existing NTC resistance detection circuit.

[0006] To achieve the above object, the technical solution adopted by the utility model is:

[0007] An NTC thermistor resistance detection circuit includes a first fixed resistor, a second fixed resistor, an NTC thermistor, a switch module, a power supply module, and a control module; the first fixed resistor and the NTC thermistor are connected in series to form a first test circuit, and the second fixed resistor and the NTC thermistor are connected in series to form a second test circuit;

[0008] Both the power supply module and the control module are electrically connected to the switch module. Under the control of the control module, the switch module performs a switching action to load the output voltage of the power supply module onto the first test circuit or the second test circuit;

[0009] One end of the NTC thermistor, the fixed resistor one and the fixed resistor two is electrically connected to the signal acquisition end of the control module, and the other end is grounded.

[0010] Further, the resistance value of the fixed resistor one is 10 kΩ.

[0011] Further, the resistance value of the fixed resistor two is 1 kΩ.

[0012] Further, a bypass capacitor is provided between the switch module and the power supply module.

[0013] Further, the capacitance value of the bypass capacitor is 100 NF.

[0014] Further, the switch module is an analog switch, and its model is TS5A3160DBVR.

[0015] Further, the control module is a single-chip microcomputer.

[0016] Due to the adoption of the above technical solution, the utility model has the following beneficial effects:

[0017] 1. The utility model does not need to measure the total voltage v of the measurement circuit, and can also measure the resistance value of the NTC thermistor, avoiding the problem of large detection errors caused by calculating the NTC resistance value by measuring the total voltage v of the measurement circuit in the prior art, and effectively improving the accuracy of the NTC resistance value measurement.

[0018] 2. The detection circuit proposed by the utility model also has the advantages of simple structure, low cost, strong stability, etc., can be applied to various application scenarios under various conditions, and has good practicability. Description of the Drawings

[0019] Figure 1 It is the circuit schematic diagram for detecting the resistance value of the NTC thermistor in the prior art;

[0020] Figure 2 It is the schematic diagram of the NTC thermistor resistance value detection circuit proposed by the utility model; Detailed Embodiments

[0021] Next, the technical solutions in the embodiments of the utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only a part of the embodiments of the utility model, rather than all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the utility model.

[0022] Embodiment 1

[0023] As Figure 2 shown, an NTC thermistor resistance detection circuit includes a first fixed resistor, a second fixed resistor, an NTC thermistor, a switch module, a power supply module, and a control module. The first fixed resistor and the NTC thermistor are connected in series to form a first test circuit, and the second fixed resistor and the NTC thermistor are connected in series to form a second test circuit. Among them, the resistance value of the first fixed resistor is 10 kΩ, marked as R15 in the figure. The resistance value of the second fixed resistor is 1 kΩ, marked as R16 in the figure.

[0024] Both the power supply module and the control module are electrically connected to the switch module. Under the control of the control module, the switch module performs on-off actions to load the output voltage of the power supply module onto the first test circuit or the second test circuit. Among them, the control module can be a single-chip microcomputer, and the switch module is an analog switch, with its model being TS5A3160DBVR, marked as U5 in the figure.

[0025] One end of the NTC thermistor connecting the first fixed resistor and the second fixed resistor is electrically connected to the signal acquisition end of the control module, and the other end is grounded. The control module collects the voltage across the NTC thermistor through an ADC.

[0026] In addition, a bypass capacitor is provided between the switch module and the power supply module, marked as C4 in the figure. The capacitance value of the bypass capacitor is 100 NF. When high-frequency noise appears in the circuit, due to the bypass capacitor presenting a low impedance to high-frequency signals, the noise current will flow to the ground through the bypass capacitor instead of entering U5, thereby ensuring that the power supply received by U5 is relatively stable and clean.

[0027] The working principle of the present utility model is as follows:

[0028] First, the control module controls the switch module to act, loading the output voltage of the power supply module onto the first test circuit. At the same time, the control module collects the voltage across the NTC thermistor through an ADC. Since the resistance value of the first fixed resistor is 10 kΩ = 10000 Ω, the formula (1) is obtained:

[0029] v / (10000 + r) = v1 / r, which is deduced to: vr = v1(10000 + r) (1)

[0030] Among them, v is the voltage value loaded on the entire circuit, r is the resistance value of the NTC thermistor, and v1 is the voltage value across the resistance value of the NTC thermistor measured when a 10KΩ resistor is in series.

[0031] Then, the control module controls the switch module to act, loading the output voltage of the power supply module onto the second test circuit. At the same time, the control module collects the voltage across the NTC thermistor through an ADC. Since the resistance value of the second fixed resistor is 1 kΩ = 1000 Ω, the formula (2) is obtained:

[0032] v / (1000 + r) = v2 / r, which is derived as: vr = v2(1000 + r) (2)

[0033] Where v2 is the voltage value across the NTC thermistor resistance measured when a 1KΩ resistor is connected in series.

[0034] Finally, from formula (1) and formula (2), formulas (3), (4), (5), and (6) can be derived:

[0035] v1(10000 + r) = v2(1000 + r) (3)

[0036] 10000*v1 + v1*r = 1000*v2 + v2*r (4)

[0037] 10000*v1 - 1000*v2 = (v2 - v1)r (5)

[0038] Finally, it is obtained that: r = (10000*v1 - 1000*v2) / (v2 - v1) (6)

[0039] It can be seen from formula (6) that in the calculation process of r, v does not need to be introduced, and the variables are only v1 and v2, and both v1 and v2 are obtained by ADC sampling through the same control module, avoiding the problem of device consistency.

[0040] The present utility model does not need to measure the total voltage v of the measurement circuit, and can also measure the resistance value of the NTC thermistor, avoiding the problem of large detection errors caused by calculating the NTC resistance value by measuring the total voltage v of the measurement circuit in the prior art, and effectively improving the accuracy of the NTC resistance value measurement. In addition, the detection circuit proposed by the present utility model also has the advantages of simple structure, low cost, strong stability, etc., and can be applied to various application scenarios under various conditions, having good practicability.

[0041] The above description is a detailed description of the preferred feasible embodiment of the present utility model, but the embodiment is not used to limit the patent application scope of the present utility model. Any equivalent changes or modifications completed under the technical spirit prompted by the present utility model shall fall within the patent scope covered by the present utility model.

Claims

1. An NTC thermistor resistance detection circuit, characterized in that: It includes a fixed value resistor 1, a fixed value resistor 2, an NTC thermistor, a switch module, a power module and a control module; the fixed value resistor 1 and the NTC thermistor are connected in series to form a test circuit 1, and the fixed value resistor 2 and the NTC thermistor are connected in series to form a test circuit 2; The power module and the control module are both electrically connected to the switch module. Under the control of the control module, the switch module performs an on-off action to load the output voltage of the power module to the test circuit 1 or the test circuit 2; One end of the NTC thermistor connected to the fixed value resistor 1 and the fixed value resistor 2 is electrically connected to the signal collection end of the control module, and the other end is grounded.

2. The NTC thermistor resistance detection circuit according to claim 1, characterized in that: The resistance of the fixed resistor 1 is 10 kΩ.

3. The NTC thermistor resistance detection circuit according to claim 2, characterized in that: The resistance of the fixed resistor 2 is 1 kΩ.

4. The NTC thermistor resistance detection circuit according to claim 1, characterized in that: A bypass capacitor is arranged between the switch module and the power module.

5. The NTC thermistor resistance detection circuit according to claim 4, characterized in that: The capacitance value of the bypass capacitor is 100NF.

6. The NTC thermistor resistance detection circuit according to claim 1, characterized in that: The switch module is an analog switch, and its model is TS5A3160DBVR.

7. The NTC thermistor resistance detection circuit according to claim 1, characterized in that: The control module is a single chip microcomputer.

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