Working principle and structure of digital pressure gauge

The digital pressure gauge is a new intelligent and multifunctional measuring instrument integrating sensor technology, electronic technology and microcomputer technology. It can not only meet the pressure measurement in the industrial field, but also can be used as a standard meter in the laboratory. The digital pressure gauge can be divided into integral type and separate type according to the structure. Most of the on-site uses are integrated, that is, sensing, conversion, and display are integrated, and they are installed in a watch case: the separated type is mostly used as a standard meter in the laboratory, and the sensor is connected to the host through a cable, and the rest The components are all installed in the main box.
Digital pressure gauge
The working principle of the digital pressure gauge is shown in the figure. The pressure of the measured medium acts on the pressure-sensitive diaphragm of the sensor. The sensor will amplify and A/D convert the sensed electrical signal and send it to the CPU for processing, and then output it in analog or digital to realize pressure display, control, and transmission. Purpose: The microprocessor can automatically compensate for the zero drift, temperature drift, non-linearity, etc. of the meter to ensure high accuracy within the use conditions of the meter.
Working principle of digital pressure gauge
There are many types of pressure sensors used in digital pressure gauges, and the commonly used ones are: piezoresistive, resistance strain, ceramic, diffused silicon, sapphire and other pressure sensors. Most of these sensors use the measuring principle of an electric bridge to convert the pressure signal into a voltage signal for processing. Now take the resistance strain sensor as an example to introduce the bridge measurement circuit. The resistance strain sensor adopts an elliptical section of a copper alloy or steel alloy tube, and its cavity is filled with the pressure medium to be measured, and 4-8 strain gauges are evenly pasted along the circumference of the tube or the cross section to form a bridge, as shown in the figure As shown in the figure, R1-R4 are strain gauges. The temperature compensation potentiometer RT and the zero adjustment potentiometer R0 are added to the bridge. When there is no pressure, the output voltage of the bridge is zero. When the cavity is under pressure, the elliptical cross section changes, which changes the resistance of the resistance strain gauge, and the bridge has an unbalanced voltage output. A voltage signal proportional to the pressure.
The schematic diagram of the bridge measurement circuit of the resistance strain type digital pressure gauge
Digital pressure gauges can be divided into two structural forms: built-in pressure module and external pressure module. The measurement accuracy of the built-in pressure module can reach 0.05% FS, but the measured pressure range usually does not exceed 600 kPa. The measurement accuracy of the external pressure module can reach 0.1% FS, and the measured pressure range can reach 60 MPa. Some also use special circuits to realize the communication between the instrument and the pressure module, and the instrument and the computer.
When the precision digital pressure gauge is equipped with a high-precision pressure sensor, it uses a microprocessor to automatically compensate for the zero drift, temperature drift, and non-linearity of the meter to ensure high accuracy within the use conditions of the meter; the precision digital pressure meter can be used as a standard The meter is used to calibrate and verify ordinary pressure gauges and pressure transmitters. For AC and DC portable precision digital meters, while measuring pressure, it can also measure current and display it on the LCD. It also has a 24VDC output to meet the needs of on-site testing and calibration.