subsequent measurement. For differential measurements without input reversal, this offset
voltage measurement is performed as part of the routine background calibration of the data
logger (see About background calibration (p. 110)). Single-ended measurement instructions
VoltSE() and TCSe() include the MeasOff parameter determines whether the offset
voltage measured is done at the beginning of the measurement instruction, or as part of self-
calibration. This option provides you with the opportunity to weigh measurement speed against
measurement accuracy. When MeasOff = True, a measurement of the single-ended offset
voltage is made at the beginning of the VoltSE() or TCSe() instruction. When MeasOff =
False, measurements will be corrected for the offset voltage determined during self-calibration.
For installations experiencing fluctuating offset voltages, choosing MeasOff = True for the
VoltSE() or TCSe() instruction results in better offset voltage performance.
If RevDiff, RevEx, or MeasOff is disabled ( = False), offset voltage compensation is
automatically performed, albeit less effectively, by using measurements from the background
calibration. Disabling RevDiff, RevEx, or MeasOff speeds up measurement time; however,
the increase in speed comes at the cost of accuracy because of the following:
l RevDiff, RevEx, and MeasOff are more effective.
l Background calibrations are performed only periodically, so more time skew occurs
between the background calibration offsets and the measurements to which they are
applied.
NOTE:
When measurement duration must be minimal to maximize measurement frequency,
consider disabling RevDiff, RevEx, and MeasOff when data logger temperatures and
return currents are slow to change.
9.11 Field calibration
Calibration increases accuracy of a measurement device by adjusting its output, or the
measurement of its output, to match independently verified quantities. Adjusting sensor output
directly is preferred, but not always possible or practical. By adding the FieldCal() or
FieldCalStrain() instruction to a CRBasic program, measurements of a linear sensor can
be adjusted by modifying the programmed multiplier and offset applied to the measurement,
without modifying or recompiling the CRBasic program. See the CRBasic Editor help for detailed
instruction information and program examples: https://help.campbellsci.com/crbasic/cr6/.
9. Tips and troubleshooting 160
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