Wide-range resistance signal acquisition circuit

Abstract

The utility model discloses a large-range resistance signal acquisition circuit, which comprises a resistor to be detected and an MCU (Microprogrammed Control Unit) for detecting voltage, the resistor to be detected is connected with a normal resistor R5, the normal resistor R5 is connected with a switching resistor R4 in parallel, the switching resistor R4 is connected with a switching circuit, the signal input end of the switching circuit is connected with the MCU, and the switching circuit is used for controlling the switching resistor R4 to be switched on and off. Sampling points are arranged at two ends of the parallel circuit of the normal resistor R5 and the switching resistor R4, the sampling points are connected to the MCU, and a power supply end is arranged at one end of the parallel circuit of the normal resistor R5 and the switching resistor R4 far away from the resistor to be tested. According to the utility model, the on-off state of the switching resistor R4 is changed through the MCU and the switching circuit, and the resistance values of the switching resistor R4 and the normal resistor R5 are changed, so that the purpose of switching the measuring range is achieved, and the sampling range of the resistance value of the temperature sensor resistor is increased.

Description

Technical Field

[0001] The utility model belongs to the technical field of sampling circuits and relates to a large-range resistance signal acquisition circuit. Background Art

[0002] When a temperature sensor is used, temperature affects the sensor's resistance. The corresponding temperature value is determined by detecting the changed resistance. Current sampling circuits for temperature sensor resistors have a narrow range of resistance variations, making them inconvenient for sampling in locations with large temperature variations. Utility Model Content

[0003] In view of the above problems, the present invention proposes a large-range resistance signal acquisition circuit, which effectively solves the problems in the prior art.

[0004] In order to achieve the above purpose, the technical solution adopted by the present utility model is as follows:

[0005] A wide-range resistance signal acquisition circuit includes a resistor to be measured and an MCU for detecting voltage. The resistor to be measured is connected to a normal resistor R5, which is connected in parallel with a switching resistor R4. The switching resistor R4 is connected to a switching circuit. A signal input end of the switching circuit is connected to the MCU. The switching circuit is used to control the on and off of the switching resistor R4. Sampling points are provided at both ends of the parallel circuit of the normal resistor R5 and the switching resistor R4. The sampling points are connected to the MCU. A power supply end is provided at the end of the parallel circuit of the normal resistor R5 and the switching resistor R4 away from the resistor to be measured.

[0006] Optionally, the switching circuit includes a resistor R10 connected in series to the MCU, the resistor R10 is connected in series with a resistor R11, a capacitor C5 and the base and emitter of the switching transistor Q2 connected in parallel, the collector of the switching transistor Q2 is connected in series with a resistor R9, the resistor R9 is connected in series with a resistor R2 and the base and emitter of the switching transistor Q1 connected in parallel, the collector of the switching transistor Q1 is connected to the switching resistor R4, and the emitter is connected to the normal resistor R5.

[0007] Optionally, the power supply end is connected in series with two diodes D1 connected in parallel.

[0008] Optionally, a clamping circuit is provided at the sampling point.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. By changing the on / off state of the switching resistor R4 through the MCU and the switching circuit, the resistance value of the switching resistor R4 and the normal resistor R5 is changed, thereby achieving the purpose of switching the range and increasing the sampling range of the temperature sensor resistance value;

[0011] 2. By setting two diodes D1 connected in parallel, when the sensor voltage is misinterpreted as a high voltage, the power supply network is protected by the diode D1;

[0012] 3. By setting up a clamping circuit, the possibility of damaging the MCU when accidentally connecting to high voltage is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a circuit diagram of an embodiment of the present utility model. DETAILED DESCRIPTION

[0014] 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 embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0015] See also Figure 1 , a large-range resistance signal acquisition circuit disclosed in an embodiment of the present utility model includes a resistor to be measured and an MCU for detecting voltage, the resistor to be measured is connected to a normal resistor R5, the normal resistor R5 is connected in parallel with a switching resistor R4, the switching resistor R4 is connected to a switching circuit, the signal input end of the switching circuit is connected to the MCU, the switching circuit is used to control the on and off of the switching resistor R4, sampling points are set at both ends of the parallel circuit of the normal resistor R5 and the switching resistor R4, the sampling points are connected to the MCU, and a power supply end is set at the end of the parallel circuit of the normal resistor R5 and the switching resistor R4 away from the resistor to be measured.

[0016] Specifically, the switching resistor R4 is connected in parallel to the normal resistor R5, and voltage sampling points are set at both ends. The on-off state of the switching resistor R4 is changed through the MCU and the switching circuit, thereby changing the resistance value of the switching resistor R4 and the normal resistor R5.

[0017] In this way, the on-off state of the switching resistor R4 is changed through the MCU and the switching circuit, and the resistance value of the switching resistor R4 and the normal resistor R5 is changed, thereby achieving the purpose of switching the range and increasing the sampling range of the temperature sensor resistance value.

[0018] For ease of understanding, the following Figure 1 Further introduction to usage scenarios.

[0019] Take the standard resistor as R0 and the measured resistor as Rx. For the convenience of introduction, set four position marks T1, T2, T3 and T4 in the circuit. The following relationship exists in the circuit:

[0020] V T1 =VT3 =V AD1 ,V T2 =V T4 =V AD0

[0021] According to the circuit principle, the following relationship can be obtained:

[0022]

[0023] Right now

[0024]

[0025] In the default state, the MCU controls the switching circuit pin to "0", and R4 is not involved in the calculation. At this time, R0 = R5. Substitute the voltages of AD0 and AD1 sampled by the MCU into formula 1 to calculate the measured resistance Rx;

[0026] When the calculated Rx is less than 0.1 times of R0, the MCU controls the switching circuit pin to "1", switches the range, and R4 participates in the calculation.

[0027]

[0028] Substitute the voltages of AD0 and AD1 sampled by the MCU into Formula 1 to calculate the measured resistance Rx.

[0029] In some feasible embodiments, the MCU uses an MCU with 12-bit AD conversion.

[0030] As a specific implementation of a large-range resistance signal acquisition circuit provided in the application, the switching circuit includes a resistor R10 connected in series to the MCU, the resistor R10 is connected in series with a resistor R11, a capacitor C5 and the base and emitter of the switching transistor Q2 connected in parallel, the collector of the switching transistor Q2 is connected in series with a resistor R9, the resistor R9 is connected in series with a resistor R2 and the base and emitter of the switching transistor Q1 connected in parallel, the collector of the switching transistor Q1 is connected to the switching resistor R4, and the emitter is connected to the normal resistor R5.

[0031] It should be understood that by providing a circuit with a switching transistor, the state of the switching transistor is controlled by the MCU, thereby controlling the switching resistor R4.

[0032] As a specific implementation of a wide-range resistance signal acquisition circuit provided in the application, two diodes D1 connected in parallel are connected in series at the power supply end.

[0033] In general, by providing two diodes D1 connected in parallel, the power supply network is protected by the diodes D1 when the sensor voltage is mistakenly high voltage.

[0034] It should be understood that the diode voltage drop varies within a certain range with the current and temperature passing through it. The voltage drop of diode D1 is V D1 , the standard input voltage of the power supply end is V0. According to the circuit principle, the following relationship can be obtained:

[0035] V T1 =V0-V D1 =V AD1

[0036] As can be seen from Formula 1, the voltage drop of diode D1 is affected by current and temperature changes and will not affect the calculation of Rx.

[0037] As a specific implementation of a wide-range resistance signal acquisition circuit provided in the application, a clamping circuit is provided at the sampling point.

[0038] It should be understood that by providing a clamping circuit, the possibility of damaging the MCU when a high voltage is mistakenly connected is reduced.

[0039] In some feasible embodiments, the clamping circuit includes a diode D2 and a diode D3 connected to the sampling terminals AD1 and AD0 respectively.

[0040] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wide range resistance signal acquisition circuit, comprising a resistor to be measured and an MCU for detecting voltage, characterized in that: The resistor to be measured is connected to a normal resistor R5, and the normal resistor R5 is connected in parallel with a switching resistor R4. The switching resistor R4 is connected to a switching circuit, and the signal input end of the switching circuit is connected to the MCU. The switching circuit is used to control the on and off of the switching resistor R4. Sampling points are provided at both ends of the parallel circuit of the normal resistor R5 and the switching resistor R4, and the sampling points are connected to the MCU. A power supply end is provided at one end of the parallel circuit of the normal resistor R5 and the switching resistor R4 away from the resistor to be measured.

2. The wide-range resistance signal acquisition circuit according to claim 1, characterized in that: The switching circuit includes a resistor R10 connected in series to the MCU, the resistor R10 is connected in series with a resistor R11, a capacitor C5 and the base and emitter of the switching transistor Q2 connected in parallel, the collector of the switching transistor Q2 is connected in series with a resistor R9, the resistor R9 is connected in series with a resistor R2 and the base and emitter of the switching transistor Q1 connected in parallel, the collector of the switching transistor Q1 is connected to the switching resistor R4, and the emitter is connected to the normal resistor R5.

3. The wide-range resistance signal acquisition circuit according to claim 1, characterized in that: The power supply end is connected in series with two diodes D1 connected in parallel.

4. The wide-range resistance signal acquisition circuit according to claim 1, characterized in that: The sampling point is provided with a clamping circuit.

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