Millipore System Documentation Set
182 Operating and Maintenance Manual Publication XITXSP121 P Rev.A
PRESSURE TRANSDUCER CALIBRATION—EXTERNAL CALIBRATION
The pressure transducers and regulator are calibrated against an external referee pressure
gauge* across the full operating span of the transducers (0–98 psig). The referee gauge
should be traceable to the NIST (National Institute of Standards Testing) or equivalent. The
calibration is conducted with an automated procedure that prompts the user through the
calibration process.
Note: Millipore recommends the use of a Setra™ Model #370 referee transducer or the
equivalent thereof. See the subsection in this chapter titled “Recommended Reference Pressure
Gauge” for details.
Calibration Criteria
Table 17: Transducer Specifications
Transducer Accuracy Specification Maximum Variance
Primary Transducer +/- 0.10 psi (0.69kPa) +/- 0.10 psi (0.69kPa)
Secondary Transducer +/- 0.33 psi (2.28kPa) +/- 0.33 psi (2.28kPa)
Pressure Regulator +/- 0.45 psi (3.10kPa) +/- 0.45 psi (3.10kPa)
Conversion Factor - 1psi = 6.89kPa 1kPa =0.145psi
Calibration curve fits:
Each of the transducers has a linear relationship vs. a referee pressure gauge. The calibration
procedure compares the referee value against the transducer readings at 6 points across the
full scale of the transducers (readings are taken at 0%, 20%, 40%, 60%, 80% and 100% of
full scale). A regression analysis is performed to determine a line of best fit and a measure of
the quality of the regression (R
2
) are calculated.
Calibration Adjustment Decisions:
• The units are only adjusted, against the manufacturer’s specifications, when
necessary (adjustments are made by changing the calibration coefficients).
• The secondary transducer and pressure regulator are matched to the primary
transducer each time an external calibration is conducted.
Calibration adjustment decisions are determined by R
2
value in Table 18.
Table 18: Calibration Adjustment Decisions (a)
R
2
Value Decision Action
< 1.82 x variance The transducer is
considered good.
No adjustments are made
to the calibration
coefficients
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