Flow Sensor
4-8 Rev 2/01
4.6.3 Zero Shift
If desired, the Zero Shift procedure can be used after calibrating the differential pressure input. The
reason for performing Zero Shift is due to the fact that the Differential Pressure is calibrated without
line pressure being applied to the sensor. When the sensor is connected back to the process after
calibration, a shift in the differential pressure can occur due to the influence of the line pressure. This
effect can be canceled out with a Zero Shift adjustment.
To check or adjust for Zero Shift, leave the sensor by-pass valve open (to simulate a no-flow
condition), with either line pressure or a normal operating static pressure from the calibrator applied to
the sensor. This applies the same pressure to both sides of the differential pressure diaphragm to give
a zero differential pressure reading.
Perform the following steps:
1.
Ensure the ROCLINK Configuration Software is connected to the flow computer and running
the calibration procedure, with the meter inputs “frozen.”
2.
In the Meter Calibration window, under the Diff Press input, select the Zero Shift pushbutton
to open the Set Zero Shift dialog box.
3.
Check the Live Reading to determine if a Zero Shift correction needs to be performed.
4.
If the reading is not zero, use the Set Zero Shift pushbutton to adjust the Zero Shift. If
adjustment is not needed, use the Done pushbutton. Either way, you are returned to the Meter
Calibration window, where you can select OK (or Done) to close the calibration window,
cancel the freeze values, and cause the flow computer to use live readings for the flow
calculations.
4.7 SPECIFICATIONS
Flow Sensor Specifications
DIFFERENTIAL PRESSURE INPUT
Range
: 0 - 250 in H
2
O (0 - 62.2 kPa)
Reference Accuracy:
±0.075% of span (includes
linearity, hysteresis, and repeatability effects) for
spans up to 10:1 turndown.
Stability:
±0.1% of upper range limit for 12 months.
STATIC PRESSURE INPUT
Range:
Absolute pressure measurement:
! 0 - 800 psia (0 -5516 kPa)
! 0 - 3626 psia (0 - 25,000 kPa)
Reference Accuracy:
±0.075% of span (includes
linearity, hysteresis, and repeatability effects) for
spans up to 6:1 turndown.
Stability:
±0.1% of upper range limit for 12 months.
PROCESS CONNECTIONS
1/4-18 NPT on 2-1/8 inch centers, located on
bottom of Sensor.
CONSTRUCTION
316 SST. Wetted O-rings are glass-filled TFE.
Coupler is stainless steel (CF8M).
ENVIRONMENTAL AND OTHER SPECS
Meets specifications described in the Main
Electronics Specifications table in Section 2.
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