Hioki DM7275-01 - Response Time

Appx.4
Measuring the Enclosure Potential of Laminated Lithium-ion Batteries
Response time
The 63% response time can be calculated using the following formula, where
R
P
indicates the
resistance between the HIGH and LOW terminals and
C
P
the capacitance between the lithium-ion
battery’s positive electrode and its enclosure aluminum:
63%responsetime=
C
P
R
P
As an example, a
C
P
value of 10 nF and an
R
P
value of 100 M
Ω
would result in a 63% response
time of 1 sec. Allow a stabilization time of (3 ×
C
P
R
P
) to (5 ×
C
P
R
P
) before measuring the voltage
after connecting the probes to the measurement target.
V
10 MΩ to1GΩ
Instrument
Setsothatinputresistance>10G
Ω
.
Contactcheck
When performing enclosure potential measurement, a voltage reading close to 0 V generally
indicates a non-defective target. However, the instrument will indicate a voltage close to 0 V even
when the probes are not connected to the measurement target due to the resistance
R
P
connecting
the HIGH and LOW terminals. Poor contact is a particular issue with the enclosure aluminum due
to the fact that it is coated with an insulating lm. Be sure to enable the instrument’s contact check
function so that you do not make judgments based on measured values obtained due to poor
contact.
Charge state
The observed voltage depends on the battery’s charge state (SOC: State of charge). To increase
the reproducibility of measurement, use as consistent a charge state as possible.
Noise countermeasures
Since the output resistance for the observed voltage is extremely high, it is necessary to implement
adequate noise countermeasures.
(1) Useshieldedwireformeasurementcablesandconnecttheshieldingtotheinstrument’sLOW
terminal.
Choose shielded wire that uses Teon or polyethylene as an insulating material (between the
shielding and the internal conductor). Shielding wire that uses polyvinyl chloride (PVC) as an
insulating material will generate an error component due to its low insulation resistance.
(2) Synchronizetheinstrument’sintegrationtimetothepowersupplycycle(PLCsetting).
(3) Besuretogroundtheinstrument’spowersupply.
R
P
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