Hioki RM3542-50, Instruction Manual

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Appendix 9 Zero Adjustment
A
16
Zero adjustment is a function which adjusts the zero point by deducting the residual value
obtained during 0
Ω measurement. For this reason, zero adjustment must be performed when
the connection is made to 0
Ω
. However, connecting a sample with no resistance is difficult
and therefore is not practical.
When performing the actual zero adjustment, create a pseudo connection to 0
Ω
and then
adjust the zero point.
To create the 0
Ω
connection state
If an ideal 0 Ω connection is made, according to Ohm's Law,
E
=
I
×
R
, the voltage between
H
POT
and L
POT
becomes 0 V. In other words, if you set the voltage between H
POT
and L
POT
to 0 V, this gives you the same state of 0 Ω connection.
To perform zero adjustment using the instrument
The instrument uses a measurement fault detection function to monitor the state of
connection between the four measurement terminals.
For this reason, when performing zero adjustment, you need to make connections between
the terminals appropriately in advance (Figure 1).
First, in order to set the voltage between H
POT
and L
POT
to 0 V, short between H
POT
and L
POT
. If
the probe lead resistances
R
SEH
+
R
SEL
are less
than a few
Ω
, there will be no problem. This is
because the POT terminal is a voltage
measurement terminal in which the current
I
0
rarely flows and is in the relational expression,
E
=
I
0
×
(
R
SEH
+
R
SEL
),
I
0
= 0. Therefore, voltage
between H
POT
and L
POT
becomes almost
0
if the
lead resistance of
R
SEH
and
R
SEL
is a few Ω .
Next, connect H
CUR
and L
CUR
. This is to avoid
display of error when no measurement current
flows through. The lead resistance of the probes
in use (
R
SOH
+
R
SOL
) must be less than or equal
to the resistance at which the measurement
current will flow.
Furthermore, when monitoring the connection
status between POT and CUR, POT and CUR must be connected. It will not be problematic
for the wiring resistance of the probes in use (
R
Short
) to be on the order of several ohms.
When wired as described above, the measurement current I flowing from H
CUR
will flow to
L
CUR
and not to the H
POT
or L
POT
wires. This enables the voltage between H
POT
and L
POT
to
be kept accurately at 0 V, and the appropriate zero adjustment becomes possible.
Appendix 9 Zero Adjustment
E = ( I
0
×
R
SEL
) + ( I
0
×
R
SEH
)
= (0
×
R
SEL
) + (0
×
R
SEH
)
= 0 [V]
Figure 1. Pseudo connection to 0 Ω