Rosemount 1154
Reference Manual
Equalize pressure to both process connections, and turn the zero adjustment until the ideal output at zero differential input is observed. Do not readjust the span potentiometer.
If the transmitter does not include zero differential pressure within its calibrated span, the zero effect or zero correction can be determined before the unit is suppressed or elevated to eliminate the zero effect after correcting for the span effect.
The following procedure illustrates how to eliminate the zero effect for a
1.Using standard calibration procedures, calibrate the unit to the required span, with the 4 mA or zero point corresponding to zero differential pressure:
4 mA at 0 inH2O and 20 mA at 400 inH2O
2.Apply static pressure to both high and low process connections with zero differential pressure across the transmitter, and note the zero correction (zero shift). For example, if the output reads 4.006 mA, the zero correction is calculated as:
4.00 mA – 4.006 mA =
Note the sign associated with this correction, as this result is added when determining the final, ideal transmitter output.
3.Remove static pressure and correct for the span effect as outlined in the span correction procedure. Calibrate the unit to the calculated output values. If, for example, the span correction procedure yielded
4.029 mA and 20.144 mA, calibrate the unit for:
4.029 mA at 100 inH2O
20.144 mA at 500 inH2O
4.Add the zero correction
4.029 mA +
5.To eliminate the zero effect, readjust the zero potentiometer so the output reads the ideal zero point calculated in step 4 (do not readjust the span potentiometer). Note that all the calibration points will shift the same amount toward the correct reading. The example output is now 4.023 mA at 100 inH2O.
The transmitter output is now
