Among various types of instruments, transmitters are the most widely used and most common, and transmitters are roughly divided into pressure transmitters and differential pressure transmitters. Transmitters are often used to measure pressure, differential pressure, vacuum, liquid level, etc. Transmitters are divided into two-wire system (current signal) and three-wire system (voltage signal). Two-wire (current signal) transmitters are especially common; there are intelligent and non-intelligent ones, and more and more intelligent transmitters; yes There are mostly electric transmitters for pneumatic and electric transmitters. In addition, there are intrinsically safe and flameproof types according to the application. When selecting models, make corresponding choices according to your needs.
1. Compatibility of the tested medium
When selecting the type, consider its medium-to-pressure interface and sensitive components, and must consider the pressure interface and the material of the sensitive components, otherwise the outer diaphragm will be corroded in a short time after use, which will cause equipment and personal accidents. Material selection is very important.
2. The influence of medium temperature and ambient temperature on the product
The temperature of the measured medium and the ambient temperature should be considered when selecting the model. If the temperature is higher than the temperature compensation of the product itself, it will easily cause the product measurement data to drift. The actual working environment of the transmitter must be considered when selecting to avoid temperature sensitivity to pressure. The core causes inaccurate measurement.
3. Selection of pressure range
The working pressure level of the equipment should be considered when selecting the model. The pressure level of the transmitter must be consistent with the application.
Fourth, the selection of pressure interface
In the selection process, strictly implement the pressure interface size used by the user, select the appropriate and correct thread connection form, and confirm the product outline drawing, or the manufacturer can provide samples;
5. Selection of electrical interface
When selecting the model, it is necessary to confirm the user signal collection method and the on-site wiring condition again and again, and the sensor signal should be connected to the user collection interface; select the appropriate and correct electrical interface and signal method.
Six, pressure type selection
An instrument that measures absolute pressure is called an absolute pressure gauge. For ordinary industrial pressure gauges, the gauge pressure is measured, that is, the pressure difference between absolute pressure and atmospheric pressure. When the absolute pressure is greater than the atmospheric pressure, the measured gauge pressure is positive, called positive gauge pressure; when the absolute pressure is less than the atmospheric pressure, the measured gauge pressure is negative, called negative gauge pressure, or vacuum. The instrument that measures the degree of vacuum is called a vacuum gauge.