Answer / carl_ellis

Something is wrong with the stated situation. The stated range is in -0.5 to 2.0 bara, where bar is bar absolute.

An absolute pressure references absolute zero (a hard vacuum).

No measurement can be made below zero bar absolute because it violates the laws of physics.

While a DP transmitter can not make a negative absolute measurement, it can make a negative differential measurement where the low side pressure is higher than the high side pressure.

The method of changing the differential range depends on the brand/model of the transmitter.
- zero and span adjusting pots
- zero and span push buttons
- local indicator/push buttons
- HART communicator/modem-software

The first two require an applied reference pressure for zero and span.

The 3rd and 4th options might have a choice of applied pressure or entering values for zero and span.

Some DP transmitters do not have the same accuracy in the negative range as they do in the positive range.

Carl Ellis
Measure First

Answer / manikandan

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