Hioki RM3542, Instruction Manual, Page: 196 / 218

Appendix 3 Unstable Measurement Values
A
6
(6)
DUT Becomes Warm
The maximum applied power to a measurement object by this instrument is determined as follows. The resis-
tance of samples with small thermal capacity can change due to heating. In such cases, enable low-power
measurement.
(7) Ingress of External Noise
Measurement should be conducted as far as possible from
devices emitting electric or magnetic fields such as power
cords, fluorescent lights, solenoid valves and PC displays.
If external noise ingress is a problem, prepare the measure-
ment leads as shown in Fig. 9.
(8) Measuring Transformers and Motors
If noise enters an unconnected terminal of a transformer or if motor rotor moves, measurements may be
unstable due to induced voltage on the measured winding. Pay attention to the treatment of unconnected ter-
minals on transformers or to motor vibration.
(9) Measuring Large Transformers or Motors
When measuring high-inductance (high-Q) DUTs such as large transformers or motors, measured values may
be unstable.
The RM3542 depends on constant current flow through the DUT, but producing constant current becomes
impossible as inductance approaches infinity. To obtain stability in a constant-current source with a large
inductance, response time is sacrificed. If you find that resistance values are scattered when measuring large
transformers or motors, please consider the above or contact your local HIOKI distributor for further assis-
tance.
Range
Measurement
Current Maximum Applied Power
= (Measured Resistance)
x
(Measurement Current)
2
100 m

100 mA 1.2 mW
1000 m

100 mA 12 mW
10

10 mA 1.2 mW
100

10 mA 12 mW
1000

1 mA 1.2 mW
10 k

1 mA 12 mW
100 k

100

A 1.2 mW
1000 k

10

A 120

W
10 M

1

A 12

W
100 M

100 nA 1.2

W
LP1000 m

10 mA 120

W
LP10

1 mA 12

W
LP100

1 mA 120

W
LP1000

100

A 12

W
Figure 9. Wiring to Minimize Noise Ingress
Twisted
Metal
Cover