Sensors and transmitters are originally concepts of thermal instruments. Sensors convert non electrical physical quantities such as temperature, pressure, liquid level, material, gas characteristics, etc. into electrical signals or directly send physical quantities such as pressure and liquid level to transmitters. A pressure transmitter amplifies the weak electrical signal collected by the pressure sensor for transmission or activation of control components.

How do we choose a good pressure transmitter? Here are six correct methods for selecting pressure transmitters:

The first thing to pay attention to is the material of the liquid: people generally consider the medium measured by the pressure transmitter. The material of the contact medium part of the pressure transmitter is generally 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then basically all pressure transmitters are suitable for measuring medium pressure.

The second factor is to look at the accuracy level: the accuracy of national standards such as China and the United States is the best part of the sensor's linearity, which is usually referred to as the accuracy between 10% and 90% of the measurement range; Because every electronic measuring instrument will have accuracy errors, but the accuracy levels marked by different countries are different. The accuracy of the European standard is the worst part of linearity, which is commonly referred to as the measurement accuracy between 0 and 10% and 90% to 100%. If the accuracy of the European standard is 1%, then the accuracy of the Chinese standard is 0.5%.

The third point is to pay attention to the range range: Generally, the maximum range measured by a sensor is 70% of the sensor's full range, which is the best. Currently, when measuring a pressure of 70 bar, the range of a pressure transmitter should be selected as 100 bar.

The fourth is to observe the temperature of the medium: As the signal of the pressure transmitter is partially converted through electronic circuits, the measured medium temperature of the pressure transmitter is generally between -30 to+100 degrees. If the temperature is too high, we usually use a condensation bend to cool the medium, which will significantly reduce the cost for manufacturers to produce a high-temperature resistant pressure transmitter specifically for you.

The fifth point is to pay attention to the measurement medium: Generally, we measure relatively clean fluids, so we can directly use standard pressure transmitters. If the medium you measure is easy to crystallize or viscous, we usually use an external diaphragm or use it together with a chemical seal to effectively prevent the medium from blocking the pressure measurement hole.

If your medium is corrosive to 316 stainless steel, then we need to use chemical sealing, which not only measures the pressure of the medium.

The sixth is the output signal: Currently, due to various acquisition needs, there are many types of output signals for pressure transmitters on the market, mainly 4-20mA, 0-20mA, 0-10V, 0-5V, and so on. However, the more commonly used are 4-20mA and 0-10V. Among the output signals I mentioned above, only 4-20mA is a two wire system (the output we mentioned is a few wire system without grounding or shielding wire), while the others are all three wire systems.