The pressure range is perhaps the most fundamental of all considerations when selecting a pressure transducer and pressure transmitter. Typically, the highest pressure a sensor is likely to experience is considered the pressure range required for the application—the full-scale pressure range of the sensor.

There are two schools of thought:

First, you could use a sensor with a range that matches the application. In such a case, the application pressure equals the sensor pressure range. This approach is the most intuitive and fairly common.

For applications where the sensor is being used for process control purposes, such as tank level measurement, the closer the sensor range is to the application range, the better. Such applications do not see huge pressure spikes and usually operate through a wide area of the pressure spectrum—not always at maximum pressure.

Second, you could down range the sensor by going with a sensor pressure range that is higher than what is required by the application. If frequent bursts or spikes in pressure can occur beyond the application pressure range, then it could be advantageous to down range the sensor. It may also be a good idea if the pressure is at or near maximum most of the time.

Down ranging means that a sensor is selected with a higher pressure range and the manufacturer calibrates the output to match the desired application pressure range.

This results in reducing the sensor resolution, and if too low, it will affect the performance accuracy of the sensor. How far to down range a sensor is completely subjective. However, the application pressure range is typically 75 percent of the full-scale range of the sensor. Following this rule-of-thumb will generally keep you out of trouble.

While neither approach is inherently right or wrong, it is important to understand the pressure characteristics of the application before selecting the pressure sensor range.