Determining Calibration Frequency; Trim The Pressure Signal; Sensor Trim Overview - Emerson Rosemount 3051P Reference Manual

Operation and Maintenance
May 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
Step 1: Determine the performance required for your application.
Required Performance:
Step 2: Determine the operating conditions.
Transmitter:
Calibrated Span:
Ambient Temperature Change:
Step 3: Calculate total probable error (TPE).
TPE =
Where:
Reference Accuracy =
Ambient Temperature Effect =
Static Pressure Effect =
Step 4: Calculate the stability per month.
Step 5: Calculate calibration frequency.
5.5

Trim the pressure signal

5.5.1

Sensor trim overview

A sensor trim corrects the pressure offset and pressure range to match a pressure standard. The upper
sensor trim corrects the pressure range and the lower Sensor trim (zero trim) corrects the pressure
offset. An accurate pressure standard is required for full calibration. A zero trim can be performed if the
process is vented.
48
2
( ) (
ReferenceAccuracy + TemperatureEffect
( ×
0.200 URL
±
Stability = --------------------------------------- - % of span for 10 years
Span
(
Req. Performance TPE
Cal. Freq. = --------------------------------------------------------------------
Stability per Month
0.50% of span
Rosemount 3051P, Range 1 [URL = 30 psi (2,1 bar)]
30 psi (2,1 bar)
± 50 °F (28 °C)
2
) (
+ StaticPressureEffect
± 0.040% of span
± (0.05% URL + 0.25% of span) per 50 °F = ± 0.3% of span
0% (does not apply to in-line products)
)
±
= 0.0017% of URL for 1 month
) (
– –
0.5% 0.303%
= ------------------------------------------- -
0.0017%
00809-0700-4001, Rev AA
2
) = 0.303% of span
)
=
118xmonths
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