65
5.7 Offset Voltage Compensation (OVC)
Function
Description
This function automatically compensates for the effects of
thermoelectromotive force (Appendix 4 Effect of Thermoelectromotive
Force (Page 173)) and internal offset voltage of the instrument.
• With the 2 Ω or higher range
Displays the true measurement value as follows by measuring R
ON
with measurement current on, then R
OFF
with measurement current
off.
• With the 20 mΩ and 200 mΩ ranges
Displays the true measurement value as follows depending on
measurement R
P
with current flow in the positive direction and
measurement R
N
with current flow in the negative direction.
5.7 Offset Voltage Compensation (OVC)
R
ON
- R
OFF
2
NP
RR +
Enabling/Disabling Offset Voltage Compensation
(SHIFT Lamp lit)
OVC lit ........ Offset Voltage Compensation enabled
OVC off ....... Offset Voltage Compensation disabled
• When the thermal capacity of the test object is small, the Offset
Voltage Compensation function may be ineffective.
• When the test object is inductive, some delay is necessary after
switching current on or off before starting measurement.
To ensure that inductance does not affect the measurement, the
delay setting should aim for about 10 times the value calculated
according to the following formula (see also 5.11.2 Trigger Delay
(Page 69)). However, auto delay sets about 100 ms delay
presuming that R and L have similar values.
L.......... Inductance of test object
R ......... Resistance of test object + test leads + contacts
I........... Measurement current (refer to 9.2 Accuracy (Page 164))
V
O
....... Open-terminal voltage (refer to 9.2 Accuracy (Page 164))
• The setting is ignored in the 100 kΩ range and higher.
• Even when a test object is purely resistive, a delay of about 1 to 10
ms is required. To adjust the delay, begin with a longer delay than
necessary, then gradually shorten it while watching the measured
value.
• If using the Zero-Adjust function, execute it after making any
changes to Offset Voltage Compensation.
• When Offset Voltage Compensation is enabled (OVC lit)
measurement time is increased.
❖ 6.3 Timing Chart; Measurement Time (Page 84)
−−=
O
V
IR
R
L
t 1ln
To Next Page
Loading...
