Rosemount 1151GP - Static Pressure Span Correction Factor

Reference Manual
00809-0100-4360, Rev BA
August 2008
4-18
Rosemount 1151
NOTE
The adjustment screw has positive stops at both ends. Forcing it beyond the
stops may cause permanent damage.
Static Pressure Span
Correction Factor
High static pressure causes a systematic span shift in the transmitter. It is
linear and easily correctable during calibration. Table 4-3 shows the amount of
span shift for range codes 3 through 8.
Table 4-3. Rosemount 1151
Analog DP/HP Span Shift.
:
The following examples illustrate a compensation method of accounting for
the span shift. For more complicated calibration conditions, contact your local
Emerson Process Management representative.
Example 1 - Refer to Table 4-3: One method is to adjust the input and allow
the transmitter output to remain at 20 mA. Use the following formula:
Corrected Input
= Desired URV + [(S  URV)  (P/1000)],
Where S = Value from Table 4-3, divided by 100.
To calibrate a Range 4 transmitter 0 to 150 inH
2
O (0 to 37.2 kPa) and correct
for 1,500 psi static line pressure, use the following correction:
Corrected Input
= 150 + [(–0.0087  150)  (1500/1000)]
= 148.04 inches
With 148.04 inches applied as input at atmospheric pressure, set the
transmitter to 20 mA. When the transmitter is exposed to 1,500 psi static line
pressure, output will be 20 mA at 150 inches input.
Where computers or microprocessor receivers are used, the mathematical
definitions used in the preceding tables can be used to automatically and
continuously make the correction.
All transmitters should be rezeroed under line pressure to remove zero error.
Example 2 - Refer to Table 4-4: A Rosemount 1151 Analog DP Range 4 with
a 4–20 mA output operating at 1,200 psi static pressure requires the output at
100% to be corrected to 20.168 mA. Therefore, the transmitter should be
adjusted from 4–20.168 mA during calibration. After installation, and with both
process inputs pressurized to 1,200 psi, readjust the zero to 4.000 mA to
remove the small zero error.
Range Code
Span Shift % Input Per 1,000 psi
316L SST Alloy C-276
3 –1.75% –1.00%
4 –0.87% –0.60%
5 –0.81% –0.70%
6 –1.45% –1.45%
7 –1.05% –1.05%
8 –0.55% –0.55%