- Metal pressure transducer transmitter accuracy is poor, but the temperature effect is small, applicable to a wide range of temperature, precision requirements of low fields.
- Ceramic pressure transducer accuracy is a little better, but by the temperature effect is relatively large, ceramic also has the advantage of impact resistance, corrosion resistance, can be used in the field of response.
- Diffuse silicon pressure transmitter precision is very high, temperature drift is also very large, so generally have to be temperature compensation, can be used. And even after temperature compensation, or can not measure the pressure over 125 ℃ above. However, at room temperature, the sensitivity coefficient of diffusion silicon is 5 times that of ceramic, so it is generally used in the field of high-precision measurement.
- Monocrystalline silicon pressure transmitter is the highest precision sensors in industrial practice, is the upgraded version of diffusion silicon, of course, the price is also upgraded. At present, in the field of monocrystalline silicon pressure transmitter is represented by Yokogawa of Japan.
Principle of different types of pressure transducer transmitter
Principle of capacitive pressure transmitter
When the pressure acts directly on the surface of the measuring diaphragm, the diaphragm produces a small deformation, and the high-precision circuit on the measuring diaphragm transforms this small deformation into a highly linear voltage signal that is proportional to the pressure and proportional to the excitation voltage, and then a special chip is used to convert this voltage signal into an industry-standard 4-20mA current signal or 1-5V voltage signal.
Principle of diffusion silicon pressure transmitter
The pressure of the measured medium acts directly on the diaphragm of the sensor (generally 316L material diaphragm), so that the diaphragm produces a micro-displacement proportional to the medium pressure, so that the sensor’s resistance changes, and the Wheatstone circuit detects this change and converts the output of a standardized measurement signal corresponding to this pressure.
Principle of Monocrystalline Silicon Pressure Transmitter
Piezoresistive pressure sensor utilizes the piezoresistive effect of monocrystalline silicon and constitutes. The use of monocrystalline silicon chip as an elastic element, when the pressure changes, the monocrystalline silicon produces strain, so that the direct diffusion of the strain resistance on the top of the strain resistance to produce a proportional change with the measured pressure, and then by the bridge circuit to obtain the corresponding voltage output signal.
Principle of ceramic pressure transmitter
Pressure directly on the front surface of the ceramic diaphragm, so that the diaphragm produces a small deformation, thick film resistor printed on the back of the ceramic diaphragm, connected to a Wheatstone bridge (closed bridge), due to the piezoresistive effect of piezoresistive resistors, so that the bridge produces a high degree of proportionality to the pressure of the highly linear, and the excitation voltage is also proportional to the voltage signal. Generally used for air compressor pressure measurement, the use of ceramic more.
Pressure transducer transmitter selection considerations
- Transmitter pressure range value selection:
First determine the system to confirm the maximum value of the measured pressure, in general, you need to choose a transmitter with a pressure range than the maximum value is also about 1.5 times the pressure range, or so that the normal pressure range, falling in the normal range of the pressure transducer transmitter 1 / 3 ~ 2 / 3, is also a common method.
2. What kind of pressure medium:
Viscous liquid, mud will plug the pressure interface, solvents or corrosive substances will not destroy the transmitter with these media in direct contact with the material.
General pressure transducer transmitter contact media part of the material used is 316 stainless steel, if the medium of 316 stainless steel has no corrosive, then basically all the pressure transmitter is suitable for the measurement of media pressure;.
If the medium is corrosive to 316 stainless steel, then we must use chemical sealing, using indirect measurement form. Such as the selection of capillary pressure guide with filled with silicone oil, play a role in preventing corrosion of the pressure transducer transmitter, extend the life of the pressure transmitter.
3. How much precision the transmitter needs:
Decide the accuracy of: non-linearity, hysteresis, non-repeatability, temperature, zero bias scale, the effect of temperature, the higher the accuracy, the higher the price. Generally choose diffuse silicon pressure transducer transmitter accuracy 0.5 level, 0.25 level, choose capacitive or monocrystalline silicon pressure transmitter, accuracy in 0.1 level, or even 0.075 level.
4. Transmitter process connection:
Usually pressure transducer transmitter, are installed into the pipeline or tank, of course, there are also a small number of matching with the flow meter installed for use. Pressure transmitter installation form usually has three: threaded, flange, clamp, so before the selection of pressure transmitter, also need to take into account the process connection, if it is threaded, more need to determine is the thread specification, is the flange should be taken into account is what kind of flange specifications of the nominal diameter and so on.
