Monocrystalline silicon pressure transmitter

The Monocrystalline Silicon Pressure Transmitter measures liquid, gas, or vapor level, density, pressure, and then converts it to a 4-20mA HART current signal output. It can also communicate with HART375 or BST Modem. Through them, parameter setting and process control. The difference from traditional pressure transmitters is that it uses nanocrystalline silicon as the sensor material.

With the development of the domestic economy, the development of the pressure transmitter market faces enormous opportunities and challenges. In the market competition, the number of pressure transmitter companies is increasing, the market is facing asymmetry in supply and demand, pressure transmitter industry has a strong demand for further reshuffle, but in some pressure transmitter market segments still There is great room for development, and information technology will become the core competitiveness.

According to the research report, by 2020, the global pressure transmitter market revenue is expected to reach 3.77 billion US dollars (about 24.8 billion yuan), a compound growth rate of 5.0%. With the ever-increasing automation of industrial production processes, the need to optimize resources, reduce costs, and improve safety has driven this market. Pressure transmitters will increase applications in the power, chemical, water supply, drainage, and pharmaceutical industries. [2]

The sensor module uses all-welding technology and has an integral overload diaphragm, a pressure sensor and a temperature sensor inside. The temperature sensor serves as a reference for temperature compensation. The positive pressure side of the pressure sensor is connected to the high pressure chamber of the sensor capsule, the negative pressure side of the sensor is connected to the low pressure chamber of the sensor capsule, and the pressure is transmitted to the silicon chip inside the sensor through the isolation diaphragm and the filling fluid, so that the pressure sensor The resistance of the chip changes, causing the output voltage of the detection system to change. The output voltage is proportional to the pressure change and then converted by the adapter unit and the amplifier into a standardized signal output. [3]

Piezoresistive pressure sensors use the piezoresistive effect of single crystal silicon. Single-crystal silicon wafer is used as an elastic element, and a single crystal silicon film is used on an integrated circuit to diffuse a set of equivalent resistances in a specific direction of the single-crystal silicon, and the resistance is connected into a bridge, and the single-crystal silicon wafer is placed thereon. Sensor cavity.

When the pressure changes, the single-crystal silicon produces strain, so that the strain resistance directly diffusing above produces a change proportional to the measured pressure, and then the corresponding voltage output signal is obtained by the bridge circuit.

Remove the flange and inspect the isolation diaphragm of sensitive parts for deformation, breakage and oil leakage.

Remove the compensation plate, do not take out sensitive parts, check the insulation resistance of the plug-in case, the insulation resistance should not be less than 100MΩ under the condition that the voltage does not exceed 100V.

Turn on the circuit and gas circuit. When the pressure signal is the upper limit of the range, turn off the gas source, and the output voltage and reading value should be stable. If the output voltage drops, the transmitter is leaking and you can use soapy water to check for leaks. [4]

1. Turn on the power and check the status of the voltage signal at the output of the transmitter. If there is no output voltage, first check whether the power supply voltage is normal; whether it meets the power supply requirements; whether there is any wiring error between the power supply and the transmitter and the load device. No voltage or reversed polarity on the transmitter terminals can cause the transmitter to output no voltage signal. Exclude the above reasons, you should further check the amplifier board circuit components for damage problems; circuit board connectors have no contact with the phenomenon of bad, can be measured against the normal instrument measurement voltage and fault meter corresponding to the measured voltage compared to the method to determine the failure Point, if necessary, replace the faulty amplifier board. When checking flow-type transmitters, special attention should be paid to J-type amplifier boards to prevent static electricity.

2. After the power is turned on, if the transmitter output is too high (greater than 10VDC) or the output is too low (less than 2.0VDC) after the input pressure signal is given, the output will be changed when the input pressure signal is changed and the zero point and span screw are changed. No reaction. For this kind of fault, in addition to checking whether there are any abnormalities in the sensitive parts of the transmitter's measurement part, check whether the “oscillation control circuit part” on the transmitter's amplifier board is working properly or not. The normal peak voltage between high-frequency transformer T1-12 should be 25~35VP-P; the frequency is about 32kHz. Secondly, check the operational status of each operational amplifier on the amplifier board; whether the components of each part are damaged or not. This type of fault requires the replacement of the amplifier board.

3, the transmitter in the line design and process assembly quality requirements are very strict, in the actual use of the line fault, after inspection and confirmation, it is best to contact the manufacturer to replace the faulty circuit board to ensure that the instrument long-term work Stability and reliability.

The clogging or installation of the primary component is not correct and the pressure point is unreasonable.

Leakage or plugging of the pressure tube, residual gas in the filling tube or residual liquid in the aeration tube, deposits in the process flange of the transmitter, forming a measurement dead zone.

The transmitter is wired incorrectly, the power supply voltage is too high or too low, indicating poor contact between the meter header and the meter terminal block connections.

The installation was not strictly in accordance with the technical requirements, and the installation method and the on-site environment did not meet the technical requirements.