Hioki RM3542-50, Instruction Manual

Page: 71 / 234

4.13 Maintaining Measurement Precision (Self-Calibration Function)
65
4
To maintain measurement precision, the instrument self-calibrates every ten minutes to compen-
sate for internal circuit offset voltage and gain drift. This function cannot be disabled.
During self-calibration, the subsequent measurement is delayed for about 6 PLC + 10 ms (PLC =
Power Line Cycles) for internal circuit compensation.
Self-Calibration Timing
Supplied power 50 Hz: 130 ms, 60 Hz: 110 ms
• When the timing of self-calibration overlaps with a measurement, self-calibration is postponed until the end
of measurement.
• When a trigger signal (measurement start signal) is applied during self-calibration, the start of the triggered
measurement is postponed until self-calibration is finished.
• Self-calibration executes automatically after changing comparator or measurement speed settings.
• During self-calibration, measurement current and the Contact Improver current are inhibited.
This function automatically compensates for offset voltage resulting from thermal emf or internal
instrument bias. (OVC: Offset Voltage Compensation)
See: "Appendix 2 Effect of Thermal emf" (p. A2)
The following value is known to be a true resistance value from R
P
(>0), the value measured with
current flowing in the positive direction, and R
N
(<0), the value measured with current flowing in the
negative direction.
Offset voltage compensation is automatically enabled in the following conditions, and cannot be modified or
disabled:
• When a range from 100 m
Ω
to 10
Ω
is selected.
• Low Power Resistance Measurement (LOW POWER ON)
When the test object is inductive, some delay [DELAY2] is required (p. 44) to allow adequate current flow
before starting measurement.
4.13 Maintaining Measurement Precision
(Self-Calibration Function)
4.14 Compensating for Thermal EMF Offset
(Offset Voltage Compensation - OVC)
R
P
R
N
–
2
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