Hioki DSM-8104, Instruction Manual

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9
3 Operating Principles
3.1 Operating Principles
Equipped with a stable measuring voltage source and high-sensitivity current measuring
unit, this meter calculates an insulation resistance value based on measuring voltage
impressed to the work and measured current value. The meter also outputs a current
value and can be used also as a high-sensitivity ammeter embedded with a voltage
source.
The control unit of the meter has a 32bit CPU for calculations of resistance values and
for other functions.
Current-voltage conversion of the current measuring unit is based on current-voltage
conversion of a charge measuring type that integrates input current. This system
features measurement of feeble current with a high accuracy by lengthening the integral
time.
The output of the current-voltage converter is converted into digital data by an A/D
converter and is fed to the memory in the control unit after being isolated by a
photoisolator.
The control unit computes measured data input to the memory and outputs it to the
display screen and interfaces.
The measuring voltage source is a variable voltage source capable of outputting
1000V/10mA and 250V/50mA maximum, supplying stable measuring voltage. The
measuring voltage source of this meter can set a large maximum output current so that
measuring time can be shortened in measuring a sample with a large electrostatic
capacity such as a capacitor by shortening the charging time.
This meter has a dedicated voltage output for charging (charging terminal), which can be
used to precharge the meter before taking measurement to enhance the measuring
throughput.
The measuring voltage output and charge output are separated by a current limiter,
enabling continual measurement without affecting measurement even if a sample on the
charge terminal side is short-circuited.
An isolated handler interface that can be connected directly to a contact signal, a GP-IB
interface conforming to the IEEE-488 standard and an RS-232 interface are available as
external interfaces that are supplied as standard provisions.
The measuring terminals can be changed to guard grounding or to measuring power
grounding by connecting a short bar on the panel.
The meter can be used as an independent ammeter by measuring a current between the
“INPUT” and “GUARD” terminals. In this case, however, measuring voltage is output on
start of measurement and a minimum value needs be set as measuring voltage.