Film pressure transmitter module

Abstract

A film pressure transmitter module adopts an operational amplifier and a plurality of peripheral components to form a signal acquisition circuit, and adopts a current loop transmitter and a plurality of peripheral components to form a current loop transmitting circuit; the signal acquisition circuit converts a resistance signal output by the pressure sensor into a voltage signal, and the voltage signal is transmitted to the current loop transmitter circuit and converted into a 4-20mA current signal; the thin film pressure transmitter module has the characteristics of simple circuit structure and few components, the cost and the size of the thin film pressure transmitter module are greatly reduced, and the low-cost application of the thin film pressure transmitter module in more fields is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of sensor signal acquisition and conversion, in particular to a thin film pressure transmitter module. Background Art

[0002] Thin film pressure sensors have been applied in many fields, such as industrial automation, medical health, environmental monitoring, smart home, etc. When thin film pressure sensors are used, they need to be used with standard signal transmitters, but the existing standard signal transmitters are expensive and large in size, which limits the large-scale application of thin film pressure sensors in certain fields. For example, electronic insoles used for gait monitoring of the elderly or rehabilitation patients are civilian wearable electronic devices that are very sensitive to price and size. If standard signal transmitters are still used, the price and size will inevitably affect the promotion and application of electronic insoles. Therefore, it is necessary to develop a low-cost and compact thin film pressure transmitter module to support the low-cost promotion and application of thin film pressure sensors in certain fields, but there are currently no low-cost and small-volume thin film pressure transmitter products on the market. Utility Model Content

[0003] In order to overcome the deficiencies in the background technology, the utility model discloses a thin film pressure transmitter module circuit design technical solution, which is used to reduce the price and volume of the standard signal transmitter used in conjunction with the existing thin film pressure sensor.

[0004] In order to achieve the purpose of the utility model, the utility model adopts the following technical solutions: a thin film pressure transmitter module, used to convert the pressure signal of the thin film pressure sensor into a 4-20mA current signal; including a signal acquisition circuit and a current loop transmission circuit; the signal acquisition circuit is connected to the thin film pressure sensor, the current loop transmission circuit is connected to an external power supply and a current signal measuring device, and the signal acquisition circuit and the current loop transmission circuit are electrically connected;

[0005] The signal acquisition circuit converts the resistance signal output by the pressure sensor into a voltage signal, which is then transmitted to the current loop transmission circuit and converted into a 4-20mA current signal. The current signal measuring device obtains the pressure value of the thin film pressure sensor by calculation based on the size of the measured current signal.

[0006] Furthermore, the current loop transmitter circuit includes a current loop transmitter U1; the current loop transmitter U1 is connected to an external power supply, and outputs a 5V power supply and a reference voltage VREF (4.096V), and the 5V power supply and the reference voltage VREF provide working power and working reference voltage for the signal acquisition circuit.

[0007] Furthermore, the signal acquisition circuit includes a reference base circuit and a signal amplification circuit; the reference base circuit includes a universal operational amplifier U2.1, and the signal amplification circuit includes a universal operational amplifier U2.2, and the universal operational amplifiers U2.1 and U2.2 are two channels of the same universal operational amplifier; the reference base circuit divides the reference voltage VREF, and outputs it through a voltage follower formed by the universal operational amplifier U2.1, and the voltage follower provides a reference base voltage for the signal amplification circuit; the signal amplification circuit compares the reference base voltage with the voltage signal of the pressure sensor, and then amplifies it through the universal operational amplifier U2.2 and outputs it to the current loop transmission circuit.

[0008] Preferably, the signal acquisition circuit includes a signal isolation circuit and a signal amplification circuit; the voltage output by the pressure sensor is isolated by a voltage follower formed by a general operational amplifier U2.1 and then input into the signal amplification circuit; the reference reference circuit uses the voltage after the reference voltage VREF is divided as the reference reference voltage of the signal amplification circuit, and after comparing it with the voltage signal output by the signal isolation circuit, it is amplified by the general operational amplifier U2.2 and output to the current loop transmission circuit.

[0009] Furthermore, an adjustable resistor VR1 is provided in the signal amplification circuit for adjusting the working range of the thin film pressure transmitter module.

[0010] Furthermore, a protection diode D1 is connected in series between the power supply V+ terminal of the current loop transmitter U1 and the external power supply.

[0011] Furthermore, a light emitting diode D2 is connected in series between the current output terminal IO of the current loop transmitter U1 and the external power supply.

[0012] Due to the adoption of the technical solution as described above, the utility model has the following beneficial effects: a thin film pressure transmitter module disclosed by the utility model is composed of only one operational amplifier, one current loop transmitter and several peripheral components, and has the characteristics of simple circuit structure and few components, which greatly reduces the cost and volume of the thin film pressure transmitter module, and enables low-cost application of thin film pressure sensors in more fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a circuit schematic diagram of a thin film pressure transmitter module of Embodiment 1;

[0014] Figure 2 This is a circuit schematic diagram of a thin film pressure transmitter module of Example 2.

[0015] In the figure: 1. Signal acquisition circuit; 2. Current loop transmission circuit; 3. External power supply; 4. Current signal measuring device; 5. Thin film pressure sensor. DETAILED DESCRIPTION

[0016] The present invention can be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. Embodiment 1:

[0017] See the instruction manual Figure 1 : A thin film pressure transmitter module, used for converting the pressure signal of a thin film pressure sensor into a 4-20mA current signal; comprising a signal acquisition circuit 1 and a current loop transmission circuit 2;

[0018] The current loop transmitter circuit 2 includes a current loop transmitter U1, a transistor Q1, and a capacitor C1. The current loop transmitter U1 is XTR116U, which has the characteristics of a wide supply voltage range (7.5V-36V), a small error (0.05%), a low nonlinear error (0.003%), a large operating temperature range (-40℃-+85℃), and a low static current (200μA). The 6th pin (pin B) of the current loop transmitter U1 is connected to the base of the transistor Q1 and the external The positive electrode of power supply 3, pin 7 (pin V+) is connected to the collector of transistor Q1, pin 5 (pin E) is connected to the emitter of transistor Q1, pin 4 (pin IO) is connected to the negative electrode of external power supply 3, pin 2 (pin IIN) is the signal current output, pin 3 (pin IRET) is the common ground terminal GND of the thin film pressure transmitter module, pin 1 (pin VREF) is the reference voltage VREF output, and pin 8 (pin VREG) is the 5V power output, which is the working power supply of signal acquisition circuit 1;

[0019] The signal acquisition circuit 1 includes a general operational amplifier, four precision resistors (R1, R2, R3, R4), and an adjustable resistor VR1; the general operational amplifier model is MCP6002T-I / SN, which has the characteristics of low static current (100μA) and a wide operating temperature range (-40℃-+85℃); the general operational amplifier includes two channels, and its working power supply is provided by the 5V power supply of the current loop transmitter U1, and its ground terminal is connected to the 3rd pin of the current loop transmitter U1;

[0020] The first channel of the general operational amplifier and the precision resistors R3 and R4 form a reference circuit to provide a precision reference voltage for the signal amplification circuit; the precision resistors R3 and R4 form a series voltage divider circuit connected between the reference voltage VREF and the ground GND, wherein the middle connection point (the reference voltage after the reference voltage VREF is divided) is connected to the positive input terminal of the first channel of the general operational amplifier, and the output terminal of the first channel is directly connected to the reverse input terminal of the first channel to form a voltage follower, so that the output voltage of the first channel of the general operational amplifier is equal to the input voltage (reference voltage) of the positive input terminal;

[0021] The second channel of the general operational amplifier, the precision resistors R1, R2 and the adjustable resistor VR1 form a signal amplification circuit; the output of the reference reference circuit (the output of the first channel of the general operational amplifier) ​​is connected to the positive input end of the second channel, the reverse input end of the second channel is connected to one end of the thin film pressure sensor 5 (without polarity distinction), the output end of the second channel is connected to the 2nd pin of the current loop transmitter U1 through the load resistor R1, the precision resistor R2 and the adjustable resistor VR1 are connected in parallel as feedback resistors between the output end and the reverse input end of the second channel, wherein the adjustable resistor VR1 is used to adjust the working range of the thin film pressure transmitter module; the other end of the thin film pressure sensor 5 is grounded GND;

[0022] A light-emitting diode D2 is also provided between the 4th pin of the current loop transmitter U1 and the negative pole of the external power supply, and the brightness change of the light-emitting diode D2 intuitively displays the pressure on the thin film pressure sensor; a capacitor C1 is also connected in parallel between the 7th pin and the 4th pin of the current loop transmitter U1 to filter out the high-frequency harmonics of the external power supply 3; a diode D1 is also provided between the 7th pin of the current loop transmitter U1 and the positive pole of the external power supply 3 to prevent the current loop transmitter U1 from being damaged when the positive and negative poles of the external power supply 3 are connected in reverse;

[0023] The diaphragm pressure transmitter module is also provided with two two-pin external sockets P1 and P2, which are used to connect to the diaphragm pressure sensor 5 and the external power supply; wherein pin 1 of the external socket P1 is connected to the ground GND, and pin 2 is connected to the reverse input terminal of the first channel of the general operational amplifier; wherein pin 1 of the external socket P2 is connected to the positive electrode of the diode D1, and pin 2 is connected to the negative electrode of the light-emitting diode D2.

[0024] The working principle of the film pressure transmitter module is as follows: when the film pressure sensor 5 is subjected to pressure, its resistance changes (the greater the pressure, the smaller the resistance), so the pressure difference on the film pressure sensor 5 (i.e., the voltage at pin 2 of the external socket P1) will change with the pressure applied to the film pressure sensor 5; the voltage at pin 2 of the external socket P1 is input into the signal amplifier circuit, compared with the reference voltage (the value of the deviation from the reference voltage is calculated, which is positively correlated with the pressure applied to the film pressure sensor 5 and is linearly related), then amplified by the signal amplifier circuit, and then converted into a current signal through a load resistor. The current signal is input into pin 2 of the current loop transmitter U1, and pin 4 of the current loop transmitter U1 is controlled to output a 4mA-20mA current signal.

[0025] Before using the film pressure transmitter module, the range calibration should be carried out. The specific calibration method is as follows: the two pins of the film pressure sensor 5 are respectively connected to the 1st and 2nd pins of the external socket P1 (without distinguishing polarity), the 1st pin of the external socket P2 is connected to the positive pole of the external power supply 3, and the calibration instrument (such as a multimeter, a PLC current signal acquisition interface) is connected in series between the 2nd pin of the external socket P2 and the negative pole of the external power supply 3; when there is no pressure on the film pressure sensor 5, the measurement value of the calibration instrument is 4mA; apply the upper limit value of the pressure measurement range (such as 10KG) to the film pressure sensor 5, and then adjust the variable resistor VR1 so that the measuring instrument displays 20mA, and the range calibration of the film pressure transmitter module is completed.

[0026] When the thin film pressure transmitter module is in use, the signal acquisition device is connected in series between pin 2 of the external socket P2 and the negative pole of the external power supply. By measuring the current value flowing through the signal acquisition device, the pressure value applied to the thin film pressure sensor 5 can be calculated; if the current value measured by the signal acquisition device is 10mA, the pressure value applied to the thin film pressure sensor 5 is 5KG, and when the current value measured by the signal acquisition device is 20mA, the pressure value applied to the thin film pressure sensor 5 is 10KG. Embodiment 2:

[0027] See the instruction manual Figure 2 : The signal acquisition circuit 1 includes a signal isolation circuit and a signal amplification circuit; the reverse input terminal and the output terminal of the first channel of the general operational amplifier are connected to form a voltage follower, and one end (without polarity distinction) of the thin film pressure sensor 5 is connected to the positive input terminal of the first channel, and is output through the output terminal of the first channel of the general operational amplifier, so that the output voltage signal of the thin film pressure sensor 5 is isolated from the signal amplification circuit;

[0028] The positive input terminal of the second channel of the general operational amplifier is connected to the middle connection point of the voltage divider circuit of the precision resistors R3 and R4 in series (the reference base voltage after the reference voltage VREF is divided); the precision resistor R2 and the adjustable resistor VR1 are connected in parallel as a feedback resistor and connected between the output terminal and the reverse input terminal of the second channel; the output terminal of the second channel is connected to the 2nd pin of the current loop transmitter U1 through the load resistor R1.

[0029] The working principle and range calibration method of the second embodiment are the same as those of the first embodiment and will not be described in detail.

[0030] The parts not described in detail in this utility model are prior art.

Claims

1. A thin film pressure transmitter module, used to convert the pressure signal of a thin film pressure sensor into a 4-20mA current signal; its characteristics are: It comprises a signal acquisition circuit (1) and a current loop transmission circuit (2); the signal acquisition circuit (1) is connected to a thin film pressure sensor (5), the current loop transmission circuit (2) is connected to an external power supply (3) and a current signal measuring device (4), and the signal acquisition circuit (1) and the current loop transmission circuit (2) are electrically connected; The signal acquisition circuit (1) converts the resistance signal output by the pressure sensor (5) into a voltage signal, and the voltage signal is transmitted to the current loop transmission circuit (2) and converted into a 4-20 mA current signal; the current signal measuring device (4) calculates the pressure value of the thin film pressure sensor according to the magnitude of the measured current signal.

2. A thin film pressure transmitter module according to claim 1, characterized in that: The current loop transmitter circuit (2) comprises a current loop transmitter U1; the current loop transmitter U1 is connected to an external power supply and outputs a 5V power supply and a reference voltage VREF; the 5V power supply and the reference voltage VREF provide a working power supply and a working reference voltage for the signal acquisition circuit (1).

3. A thin film pressure transmitter module according to claim 2, characterized in that: The signal acquisition circuit (1) includes a reference base circuit and a signal amplification circuit; the reference base circuit includes a universal operational amplifier U2.1, and the signal amplification circuit includes a universal operational amplifier U2.2, wherein the universal operational amplifiers U2.1 and U2.2 are two channels of the same universal operational amplifier; the reference base circuit divides the reference voltage VREF and outputs the voltage through a voltage follower formed by the universal operational amplifier U2.1, and the voltage follower provides a reference base voltage for the signal amplification circuit; the signal amplification circuit compares the reference base voltage with the voltage signal of the pressure sensor and amplifies the voltage through the universal operational amplifier U2.2 and outputs the voltage to the current loop transmission circuit (2).

4. A thin film pressure transmitter module according to claim 2, characterized in that: The signal acquisition circuit (1) includes a signal isolation circuit and a signal amplification circuit; the voltage output by the pressure sensor (5) is isolated by a voltage follower formed by a general operational amplifier U2.1 and then input to the signal amplification circuit; the reference reference circuit uses the voltage value after the reference voltage VREF is divided as the reference reference voltage of the signal amplification circuit, compares it with the voltage signal output by the signal isolation circuit, and then amplifies it through the general operational amplifier U2.2 and outputs it to the current loop transmission circuit (2).

5. A thin film pressure transmitter module according to claim 3 or 4, characterized in that: An adjustable resistor VR1 is provided in the signal amplification circuit for adjusting the working range of the film pressure transmitter module.

6. A thin film pressure transmitter module according to claim 2, characterized in that: A protection diode D1 is connected in series between the power supply V+ terminal of the current loop transmitter U1 and the external power supply (3).

7. A thin film pressure transmitter module according to claim 2, characterized in that: A light emitting diode D2 is connected in series between the current output terminal IO of the current loop transmitter U1 and the external power supply (3).

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