Important Characteristics Of A Differential Pressure Transmitter
This article discusses some of the important characteristics of a differential pressure transmitter that is designed to be capable of measuring the pressure caused by vapors, liquids, and gases. One example of this kind of device is the Rosemont transmitter that has an excellent stability for at least five years of installation. These products are ready to install once they arrive from the manufacturer, having been pressure tested and calibrated in the factory. It should be noted that the pressure transmitter is slightly different than the pressure sensor because it has electronic circuits that provide it with the capability to transmit the output signal to a control panel. This may make it suitable for use as wireless industrial pressure sensors. It should be pointed out that previously, the transmitter could easily be distinguished because it was larger than the pressure sensor. However, because of the shrinking of the size of the differential pressure transmitter, it has become difficult to differentiate it from the pressure sensor just by looks.
The differences between the differential pressure transmitter and the transducer have been blurred further with the emergence of amplified voltage output pressure transducers. The latter devices have sufficient signal strength to transmit output signals over longer distances compared to the strain gauge output pressure transducer. However, they have less power compared to the output signals of the transmitters. As a general guideline, if the differential pressure sensor is provided with a current loop output then it is a pressure transmitter.
Another important characteristic that has to be considered when choosing a differential pressure transmitter sensor is the minimum voltage that must be applied across its two ends. Any load resistance that is added in series to the device will cause a drop in the voltage that is applied across the ends of the sensor. To calculate the actual voltage that is left to powering the transmitter, the voltage drop across the resistance must be subtracted from the voltage available from the main circuit. Of course, a more complex electrical analysis may be required if the circuit is not a simple series arrangement.
Aside from being careful not to have a voltage that is lower than the rated voltage of the differential pressure transmitter, it is also vital to make sure that the actual voltage does not exceed the maximum voltage rating. Even a slight overvoltage may cause internal heating that may substantially affect the performance characteristics of the pressure transmitter. It is advisable to be careful when reading the technical data sheet that is provided by the manufacturer. Some with specify the voltage across the two ends of the transmitter while others will indicate the voltage of the power supply. Some data sheets may also provide a load diagram that will indicate the permitted region of operation for a particular supply voltage and load. Meanwhile, another important factor to consider is the pressure reference. Oftentimes, this is a gauge reference or a vented gauge and this means that the opposite side of the sensing diaphragm is open and subjected to atmospheric pressure.
