Emerson 00809-0100-4102 manual Calculate calibration frequency

Section 5: Operation and Maintenance	Reference Manual
May 2013	00809-0100-4102, Rev AA

Sample calculation for 2051 (0.04% accuracy & 5-year stability)

Step 1: Determine the performance required for your application.

Required Performance:	0.20% of span
Step 2: Determine the operating conditions.
Transmitter:	2051CD, Range 2 [URL=250 inH2O(623 mbar)]
Calibrated Span:	150 inH2O (374 mbar)
Ambient Temperature Change:	± 50 °F (28 °C)
Line Pressure:	500 psig (34,5 bar)

Step 3: Calculate total probable error (TPE).

TPE = (ReferenceAccuracy)2 + (TemperatureEffect)2 + (StaticPressureEffect)2 = 0.105% of span

Where:
Reference Accuracy =	± 0.04% of span
Ambient Temperature Effect =⎛	(-----------------------------------------0.0125× URL) + 0.0625⎞ % per 50 °F = ±0.0833% of span
⎝	Span	⎠

Span Static Pressure Effect(1) =

0.1% reading per 1000 psi (69 bar) = ±0.05% of span at maximum span

(1)Zero static pressure effect removed by zero trimming at line pressure.

Step 4: Calculate the stability per month.

Stability = ±

(0.125 × URL)

--------------------------------------

Span

% of span for 5 years = ±0.0021% of URL for 1 month

Step 5: Calculate calibration frequency.

Cal. Freq. =	(----------------------------------------------------------------------Req. Performance – TPE)	=	(---------------------------------------------0.2%– 0.105%)	= 45xmonths
	Stability per Month		0.0021%

5.3.3Compensating for Span line pressure effects (range 4 and range 5)

Rosemount 2051 Range 4 and 5 pressure transmitters require a special calibration procedure when used in differential pressure applications. The purpose of this procedure is to optimize transmitter performance by reducing the effect of static line pressure in these applications. The 2051 differential pressure transmitters (ranges 0 through 3) do not require this procedure because optimization occurs at the sensor.

The systematic span shift caused by the application of static line pressure is -0.95% of reading per 1000psi (69 bar) for Range 4 transmitters, and -1% of reading per 1000psi (69 bar) for Range 5 transmitters. Using the following procedure, the span effect can be corrected to ±0.2% of reading per 1000 psi (69 bar) for line pressures from 0 to 3626 psi (0 to 250 bar).

Use the following example to compute correct input values.

66 Operation and maintenance