3550 Battery HiTESTER Series
12
Q8. Why do the 3550 series use the
AC four-terminal method?
A8. There are basically two general methods for
checking battery deterioration: the
charging/discharging test method, and
measuring the internal resistance. Each
method has its own strengths and
weaknesses. The charging/discharging test
method is capable of accurately measuring
the discharge capacity of the battery. On the
other hand, this method requires a
considerable amount of time. Measuring the
internal resistance, however, evaluates the
deterioration of the battery on the basis of the
correlation between the measured internal
resistance and the discharge capacity of the
battery. While the accuracy of the measured
results suffers somewhat, the test can be
conducted very quickly and the test equipment
can be fairly small. In resistance
measurement, the four- terminal method is
used to measure items, such as batteries, that
have very low resistance. The AC four-
terminal method is illustrated below. The
input impedance of the voltmeter is large, so
practically no test current flows to the
voltmeter. As a result, it is possible to
measure the resistance of the subject only,
with the lead resistance and the contact
resistance excluded.
Q9. Why does the zero adjustment
board have to be removed at
least 10 cm from the unit when
performing zero adjustment?
A9. The electromagnetic field generated in the
loop formed by the zero adjustment board and
the measurement leads would otherwise
affect operation of the unit. Care must also
be taken not to have any other metal objects
in the vicinity of the zero adjustment board,
because magnetic influences can falsify the
measurement.
Q10. After performing zero
adjustment with the 9460 CLIP-
TYPE LEADS WITH
TEMPERATURE SENSOR, is it
possible to change leads and
take a measurement with the
9465 PIN- TYPE LEADS?
A10. Measurement precision is assured only with
the same lead that was used for zero
adjustment. However, in the 300 mΩ,3
Ω,and 30 Ω ranges, the measurement lead
influence can be largely disregarded.
Q11. Performing renewed zero
adjustment every time is a
bother. Is it possible to retain
adjustment data while the unit is
turned off?
A11 Zero adjustment data are written to volatile
memory and are therefore lost when power is
turned off. Zero adjustment must be
performed every time when the unit was
turned off.
Q12. Why is the display value
different from the calibration
value when performing
calibration? *See also Q 6 and
A 6.
A12. [Resistance measurement]
Is the AC 1 kHz resistance value being used
for calibration? The AC calibration value and
DC calibration value do not necessarily match.
The DC calibration value is a true resistance
value, whereas the AC 1 kHz calibration value
is an rms value. These will normally be
R1 to R4: Lead resistance and contact
resistance
C: Coupling Capacitor
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