Determining Calibration Frequency - Emerson Rosemount 2051 Reference Manual

Reference Manual
00809-0300-4101, Rev BB
5.4

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 a standard Rosemount 2051C
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 total probable error (TPE).
TPE =
where:
Reference accuracy = ± 0.065% of span
Ambient temperature effect =
Span static pressure effect
1.
Step 4: Calculate the stability per month.
Stability =
Step 5: Calculate calibration frequency.
CaIibration frequency
Calibration
2
( )
ReferenceAccuracy
±
(1)
= 0.1% reading per 1000 psi (69 bar) = ±0.05% of span at maximum span
Zero static pressure effect removed by zero trimming at line pressure.
0.100% URL
 
±
% of span for 3 years = ±0.0046% span per month
---------------------------------- -
 
Span
(
Required 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
( )
TemperatureEffect
+ +
0.025% URL
 
0.125 per 50 °F
---------------------------------- - +
 
Span
)
–
=
Calibration
November 2016
O [623 mbar])
2
2
( )
StaticPressureEffect = 0.189% of span
±
0.1666% of span
=
( )
–
0.3% 0.189%
------------------------------------------- - = 25months
0.0069%
47