NF DM2571, User Manual

Page: 357 / 369

APPENDIX
353
Measuring Characteristics
Speed Digits
Reading Rate
(Readings/sec) RTD/TCO/
Thermistor
5/s 6 ½
20/s 5 ½
60(50)/s 4 ½
[1]. The actual measurement range and test lead error will be constrained
by the adopted test lead. The test lead accuracy adder covers all errors of
measurements and ITS-90 temerature change.
Capacitance
[1]
Range
1 Year
TCAL ± 5 ˚C Temperature
Coefficient/
˚
C
1.000 nF
[2]
2.00 + 2.00 0.05 + 0.01
10.00 nF
2.00 + 1.00 0.05 + 0.01
100.0 nF 2.00 + 0.40 0.05 + 0.01
1.000 μF 2.00 + 0.40 0.05 + 0.01
10.00 μF 2.00 + 0.40 0.05 + 0.01
100.0 μF
2.00 + 0.40 0.05 + 0.01
Accuracy Specifications: ± ( % of r % of range )
[1]. Specifications are for film capacitor inputs that are greater than 10% range.
[2]. Accuracy at 1nF range is supplementary value.
Measuring Characteristics
Measurement method: DC recharge & discharge.
Input protection: 500 Vpeak on all ranges.
The capacitor under test (Cx) is charged using a constant current source. The
time to charge Cx is recorded. The capacitor is then discharged using a known
resistance and the discharge time is recorded. The value of the resistance depends
on the capacitance range that is selected. The charge and discharge time is used
to calculate the capacitance of Cx if the selected capacitance range is equal to or
less than 10 nF. Only the charge time is used to calculate the capacitance of Cx if
the selected capacitance range is equal to or greater than 100 nF.
As measuring capacitance with the DMM is effectively a DC measurement, the
measured capacitance tends to be higher than what is measured by LCR meters.
For best measurement results, first perform a zeroing of the test leads when the
cables are “open” to compensate for the test lead capacitance.