NF ZM2371 - Page 114

4.7 Setting the Contact Check
4-27 ZM2371/ZM2372
 Operational outline of 4-terimnal contact check
For ZM2372, before normal measurement, it is possible to check the contact status of each
terminal by monitoring the resistance value between both terminals after applying the small
test signal onto between H
CUR
-H
POT
and also between L
CUR
-L
POT
while the contact check is
enabled. Once the contact failure is detected, ZM2372 allows the measured value “NC” to
appear without performing normal measurement.
The additional time necessary for 4-terminal contact check is approx 4ms.
The test signal of contact check becomes OFF during normal impedance measurement.
(a) Contact check operation timing (b) Contact check circuit
Figure 4–6 4-terminal contact check
If the contact is normal, unnecessary signal can not be applied in the DUT during contact
check. In contact failure, it is possible that up to 3V and 50μA signal can be applied in the
DUT. For the polarity of test signal to be applied in the DUT during contact failure, H
CUR
and H
POT
side becomes plus against L
CUR
and L
POT
side.
 Criterion for contact failure
For ZM2372, in 4-terminal contact check, if the resistance value between H
CUR
-H
POT
terminals or between L
CUR
-L
POT
terminals exceeds 200Ω, it should be judged as contact
failure.
A
R
R
DUT
A
R
R
TRIG
Measurement signal
output
Signal acquisition
time
Parameter
calculation
Measured value
/INDEX
/EOM
Trigger delay time
Contact check