Emerson 3051S Specifikace stáhnout pdf (Strana 97)

Reference Manual

00809-0200-4801, Rev CA

July 2010

6-19

Rosemount 3051S

The case of the Differential Pressure measurement in a flow application with a

single line plugged is more complicated, and the behavior of the transmitter

may vary depending on a number of factors. First the basics: a differential

pressure transmitter in a flow application is equipped with two impulse lines,

one on the high pressure side (HP) and one on the low pressure side (LP) of

the primary element. Understanding the results of a single plugged line

requires understanding of what happens to the individual pressure signals on

the HP and LP sides of the primary element. Common mode noise is

generated by the primary element and the pumping system as depicted in

Figure 6-17. When both lines are open, the differential pressure sensor

subtracts the LP from the HP. When one of the lines are plugged (either LP or

HP), the common mode cancellation no longer occurs. Therefore there is an

increase in the noise of the DP signal. See Figure 6-18.

Figure 6-17. Differential

Pressure Signals under Different

Plugging Conditions

Figure 6-18. Differential

Pressure (DP) Signals under

Different Plugged Conditions

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Emerson 3051S Specifikace Strana 97