Answer / carl_ellis

How does any DP cell make a measurement?
Ans: High side pressure minus low side pressure

What does a drum level DP cell measure?

A DP transmitter measures the difference in pressure
between
- the water level in the drum (and steam pressure) and
- the water in a static column (and steam pressure), also
called the “Reference Leg”.

The DP's low side is connected to the reference leg which
extends to the top and is filled with water.

The DP's high side is connected to a low point in the
boiler drum.

What happens (algebraically) when a large number is
subtracted from a small number? For instance, 5 - 10 = -5

What are the relative values that are being subtracted from
each other in the DP cell?

Carl Ellis
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