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Function characteristics and selection attention of compact pressure transmitter

Release time:2023-02-14Click:83

Function characteristics of compact pressure transmitter products, manufacturer's fault maintenance methods and points for attention in selection.


The compact pressure transmitter uses an imported diffused silicon or ceramic piezoresistive sensor as the pressure detection element. It adopts the micro-melting technology, which uses high-temperature glass to melt the micro-machined silicon varistor onto a stainless steel film. The glass bonding process avoids the effects of temperature, humidity, mechanical fatigue and media on the glue and material, thus improving the long-term stability of the sensor in the industrial environment. This series of oil pressure transmitter also belongs to a class of 316 pressure transmitters. Because of its small size, it is called compact pressure transmitter


Principle:

The pressure sensitive element of the compact pressure sensor is a diffused silicon core. The principle is that when the pressure core in the transmitter is under pressure, the diaphragm produces A small deformation, the Wheatstone bridge composed of four semiconductor resistors on the diaphragm, the piezoresistion effect is converted into an electrical signal, and finally converted into a 4-20mA standard current signal output by V/A voltage and current, which corresponds linearly to the pressure of the measured medium (liquid).


1, small size, light weight, can be installed in a narrow position.


2, integrated special chip, less discrete components, good temperature characteristics.


3, easy to operate, maintenance and repair.


4. With reverse polarity and current limiting protection;


5. Laser resistance temperature compensation;


6. Zero and measuring range can be adjusted on site (with watch head);


7. Wide range of corrosion resistance, suitable for a variety of media;


8. Strong overload and anti-interference ability, stable performance;


9. Small size, light weight, can be installed in a narrow position;


In order to select a good compact pressure transmitter, several parameters need to be clear:


1. Pressure range; 2, the use of temperature range; 3, the measured medium; 4, measurement accuracy; 5, output signal; 6, interface size, etc

Pressure range, that is, to measure the minimum pressure and maximum pressure difference. General pressure transmitter has 1.5 times overload capacity.

Operating temperature range, minimum operating temperature and maximum operating temperature. Generally, it is -20 ~ 80℃. If the temperature is high, other cooling measures should be added.




Select compact pressure transmitter should pay attention to 6 points:


1, pressure range: that is, to measure the minimum pressure and maximum pressure difference. General pressure transmitter has 1.5 times overload capacity.


2, the use of temperature range: the lowest use temperature and the highest use temperature. Generally, it is -20 ~ 80℃. If the temperature is high, other cooling measures should be added.


3, the measured medium: with the different measured medium, the pressure transmitter requirements are different. For example, acid and alkali resistance, ceramic sensor is better. The shell is resistant to acid and alkali.


4, measurement accuracy: in general use, the accuracy of 0.5% is more. If you want a more accurate measurement, you can ask for a measurement accuracy of 0.2%, or 0.1%.


5, output signal: is the relevant use of secondary instrument can accept what signal. Most use 4 ~ 20mA, but there are other 0-5V, 0-10V or 0 ~ 20mA output signals.


6, interface size: according to the customer site use conditions, processing the corresponding installation size


Compact pressure transmitter in the process of use will inevitably appear a variety of failures, its influence factors are numerous, such as the compact pressure transmitter between the diaphragm and the sensor element of the filling fluid leakage, zero and range offset, output instability will lead to the compact pressure transmitter precision decline and even damage; Weather factors will also affect the transmitter, such as lightning will damage the circuit of the transmitter membrane box, resulting in no communication; Wet conditions can damage wiring; The range selection of the transmitter will cause irreversible deformation of the transducer. The following describes common fault types:


(1) The line is faulty. When there is a line fault, the computer display value is abnormal, open the terminal box of the transmitter, check whether there is virtual connection, short connection or broken connection of the line, and troubleshoot the fault by measuring the power supply, shaking insulation and measuring resistance.


(2) frequency conversion interference. When wiring, a variety of signal lines interfere with each other, especially in the power line and signal line string in the same pipeline, the interference effect is more serious, in this case will lead to transmitter communication or even error. This error can be avoided by increasing the distance between the instrument cable and the power cable bracket.


(3) The pressure lead pipe is faulty. Pressure tube failure usually has three fault types: blockage of pressure tube, leakage of pressure tube and liquid accumulation of pressure tube. Blockage of pressure tube is generally caused by untimely discharge or dirty and sticky media. The leakage of the pressure tube is caused by the electrical connection of the transmitter, the cut-off valve and other accessories, which increases the leakage point; The fluid accumulation in the pressure primer is usually caused by unreasonable gas pressure taking method or incorrect installation of the pressure primer. The fluid accumulation in the pressure primer will affect the measurement accuracy.


(4) Electrical signal transmission failure. Small pressure transmitter if the use or maintenance of improper easily lead to electrical signal transmission fault, such as in order to save time on the transmitter near the equipment under test, resulting in signal transmission distance is too far, the signal will appear interference or attenuation phenomenon, at this time to increase the cross-sectional area of the cable line according to the need.


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