Determining Calibration Frequency - Emerson Rosemount 3051S Series Reference Manual

Reference Manual
00809-0100-4801, Rev HA
Calibrate the 4–20 mA output
4–20 mA Output Trim

4–20 mA Output Trim Using Other Scale

Data flow can be summarized in four major steps:
1. A change in pressure is measured by a change in the sensor output (sensor signal).
2. The sensor signal is converted to a digital format that is understood by the microprocessor
(Analog-to-Digital signal conversion).
3. Corrections are performed in the microprocessor to obtain a digital representation of the process
input (Digital PV).
4. The Digital PV is converted to an analog value (Digital-to-Analog signal conversion).
Not all calibration procedures should be performed for each transmitter. Some procedures are
appropriate for bench calibration, but should not be performed during field calibration.
identifies the recommended calibration procedures for each type of transmitter for bench or field
calibration.
4.2.2

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
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:
Operation and Maintenance
(page 79); or
(1)
2
( ) (
ReferenceAccuracy + TemperatureEffect
(page 80)
0.30% of span
Rosemount 3051S_CD, range 2A
[URL= 250 inH O(623 mbar)], classic performance
2
150 inH O (374 mbar)
2
± 50 °F (28 °C)
500 psig (34.5 bar)
2 2
) ( )
+ StaticPressureEffect
Operation and Maintenance
= 0.112% of span
October 2018
Table 4-1
75