Determining Calibration Frequency - Emerson Rosemount 2051 Reference Manual

Operation and Maintenance
July 2017
5.4.2

Determining calibration frequency

Calibration frequency can vary greatly depending on the application, performance requirements, and
process conditions. Use the following procedure to determine calibration frequency that meets the
needs of your application:
1. Determine the performance required for your application.
2. Determine the operating conditions.
3. Calculate the Total Probable Error (TPE).
4. Calculate the stability per month.
5. Calculate the calibration frequency.
Sample calculation for Rosemount 2051
Step 1: Determine the performance required for your application.
Required Performance:
Step 2: Determine the operating conditions.
Transmitter:
Calibrated span:
Ambient temperature change:
Line pressure:
Step 3: Calculate TPE.
TPE =
Where:
Reference accuracy =
Ambient temperature effect =
Span static pressure effect
1. Zero static pressure effect removed by zero trimming at line pressure.
Step 4: Calculate the stability per month.
Stability
Step 5: Calculate calibration frequency.
Cal. Freq.
Sample calculation for Rosemount 2051C with P8 option
(0.05% accuracy and 5-year stability)
Step 1: Determine the performance required for your application.
Required performance:
64
2
(Reference accuracy) + (Temperature effect)


(1)
=
  
0.100 URL
 ------------------------------------- - % of span for 2 years
=
Span
 Req. Performance TPE 
–
= -------------------------------------------------------------------- =
Stability per Month
0.30% of span
Rosemount 2051CD, range 2 (URL=250 inH
150 inH O (374 mbar)
2
± 50 °F (28 °C)
500 psig (34,5 bar)
2 2
+
(Static pressure effect)
± 0.065% of span
  
0.025 URL
 % per 50 °F
------------------------------------- - + 0.125

Span
0.1% reading per 1000 psi (69 bar)

= 0.0069% of URL for 1 month
 0.3% 0.189% 
–
------------------------------------------- - = 16xmonths
0.0069%
0.30% of span
Reference Manual
00809-0100-4107, Rev CA
O[623 mbar])
2
= 0.189% of span

= 0.167% of span
=  0.05% of span at maximum span
Operation and Maintenance