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Reference Manual
00809-0100-4808, Rev CA
June 2008
Rosemount 3051N
2-20
NOTE
Use a precision resistor for optimum accuracy. If you add a resistor to the
loop, ensure that the power supply is sufficient to power the transmitter to a
20 mA output with the additional loop resistance.
Compensating
Rosemount 3051N Range
4 and 5 Differential
Transmitters for
Line Pressure
Rosemount 3051N Range 4 and Range 5 pressure transmitters require a
special calibration procedure when used in differential pressure applications.
The purpose of this procedure is to optimize transmitter performance by
reducing the effect of static line pressure (P
s
) in these applications.
Rosemount 3051N differential pressure transmitter ranges 0, 1, 2, and 3 do
not require this procedure because the optimization occurs in the sensor. See
“Static Pressure Effect” on page 5-3 for additional details.
Applying high static pressure to Rosemount 3051N Range 4 and Range 5
pressure transmitters causes a systematic shift in the output. This shift is
linear with static pressure; correct it by performing the “Full Trim” on
page 2-18, after determining the corrected input values as noted below.
The following specifications show the static pressure effect for Rosemount
3051N Range 4 and Range 5 transmitters used in differential pressure
applications:
Zero Effect:
±0.1% of the upper range limit per 1000 psi (6,9 MPa) for line pressures
(P
s
) from 0 to 2000 psi (0 to 13,8 MPa)
±[0.2 + 0.2 (P
s
-2000) / 1000]% of the upper range limit per 1000 psi
(6,9 MPa) for line pressures above 2000 psi (13,8 MPa) and ≤ 3626 psi
(25 MPa)
Span Effect:
Correctable to ±0.2% of reading per 1000 psi for line pressures from 0 to
3626 psi.
The systematic span shift caused by the application of static line pressure is
–1.00% of input reading per 1000 psi for 3051N Range 4 transmitters, and
–1.25% of reading per 1000 psi for Range 5 transmitters.
Use the following example to compute corrected input values.
Example
A Rosemount 3051ND4 transmitter will be used in a differential pressure
application where the static line pressure is 1200 psi. The transmitter is
ranged so that the output is 4 mA at 500 inH
2
O and 20 mA at 1500 inH
2
O.
To correct for systematic error caused by high static line pressure, first use
the following formulas to determine corrected values for the low trim and
high trim.
LT
c
= LRV + S (LRV) P
s
Where: LT
c
= Corrected Low Trim Value
LRV = Lower Range Value
S = –(Systematic Span shift per specification)
P
s
= Static Line Pressure