Why is the output of my pressure sensor quoted in mV/V?

The mV/V output allows you to eliminate much of the error due to power supply voltage change.

A mV/V output implies that different levels of excitation may be provided to the transducer. The full-scale output of the transducer varies directly with the excitation. A sensor with a calibration factor of 3 mV/V will exhibit 30 mV at full pressure if it is being supplied with 10 V power, but only 15 mV at full pressure if it is being supplied with 5 V.

Output varies with supply voltage. If we don’t know how much the change in supply voltage effected our output, then we cannot possibly know how much our change in output was due to an actual change in pressure.

Many users monitor transducer output AND power supply excitation. Changes in output are compared to the supply voltage to discount effects from voltage shifts. Using the mV/V relationship, users can tell how much of their output change was due to an actual change in pressure.

This approach is known as a ratio metric approach because it relies on the ratio of voltage output to the Calibration Factor (mV/V) to determine pressure.

For example, if we have a 3 mV/V, 100 lb load cell: