Crystal nVision Reference Recorder - Measurement Uncertainties for Two Pressure (PM) Modules Using Tare Function; Measurement Uncertainties for Two Pressure (PM) Modules Without Tare

nVision Operation Manual • Page 27
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Measurement.Uncertainties.for.two.Pressure.(PM).Modules.using.Tare.
Function
The Tare function can improve measurement uncertainties on two modules with the same full
scale pressure range installed into one nVision Reference Recorder.
The following specications apply to the measurement system:
The greater of
Full Scale Range
of Both Sensors
PSI PSI mbar inH2O % of DP Reading
30 0.0015 0.10 0.042 or 0.025%
100 0.0040 0.28 0.11 or 0.025%
300 0.015 1.0 0.42 or 0.025%
1 000 0.04 2.8 1.1 or 0.05%
3 000 0.15 10.3 4.2 or 0.05%
10 000 0.4 27.6 11.1 or 0.1%
Due the additional digit of resolution in dierential mode some units may be inappropriate due
to the noise oor of the reading.
The following chart indicates the expected resolution on the appropriate units:
PSI bar kPa/MPa kg/cm
2
PSI kg/cm
2
inHg inH
2
O mmHg mmH
2
O kPa bar mbar MPa
30 3 300 3 0.0001 0.00001 0.0001 0.001 0.001 0.00001 0.01
100 10 1 10 0.0001 0.00001 0.001 0.01 0.001 0.00001 0.01
300 30 3 30 0.001 0.0001 0.001 0.01 0.01 0.0001 0.1 0.00001
1 000 100 10 100 0.01 0.0001 0.01 0.01 0.01 0.0001 0.1 0.00001
3 000 300 30 300 0.01 0.001 0.01 0.1 0.001 0.0001
10 000 700 70 700 0.1 0.001 0.1 0.001 0.0001
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Measurement.Uncertainties.for.two.Pressure.(PM).Modules.without.Tare
The total nVision Reference Calibrator measurement uncertainty in the ∆P mode conguration
will need to consider the uncertainties of both pressure modules. Crystal Engineering recom-
mends the module uncertainties to be combined with the preferred square root of the sum of
the squares (or “root sum squares”) method.
The following table lists the possible combinations of combining Pressure Modules (PM) with
dierent accuracy statements. The uncertainties reported below are without using the Tare
feature which will greatly improve your measurement uncertainty.
Upper Pressure Module Uncertainties
(of Static Line Pressure) (of Reading)
0.025% 0.05% 0.10%
Lower Pressure
Module Uncertainties
(of Static Line Pressure)
(of Reading)
0.025% 0.035% 0.056% 0.103%
0.05% 0.056% 0.071% 0.112%
0.10% 0.103% 0.112% 0.141%