Current Measurement - Fluke 8062A Instruction Manual

The ac input voltages are divided with the same divider arrangement as the
dc input voltages, with the exception that the 2V ac voltage range is divided
by 10. The divider output signals for ac voltages are ac-coupled to the input
of a true rms ac converter which produces a current output. A negative dc
representation of the ac input signal is filtered and applied to the input of the
a/d converter.
Function
DC Voltage
AC Voltage
*Integrator gain in a/d converter reduced by factor of 10.
3-7.

Current Measurement

Current measurements are made using a double-fuse-protected, switchable,
five-terminal current shunt (0.1 ohm, 1 ohm, 10 ohm, 100 ohm or 1 kilohm)
to perform the current-to-voltage conversion required by the a/d converter. A
block diagram of current measurements is shown in Figure 3-5. When the dc
current function is selected, the dc voltage drop across the shunt is filtered
and applied to the input of the a/d converter. When the ac current function is
selected the ac voltage drop across the shunt is ac-coupled to the input of the
true rms ac converter. The dc representation of the ac voltage is filtered and
applied to the input of the a/d converter. All current ranges use the 200 mV
a/d converter input range.
Table 3-1. Voltage Input Divider
Input
Range
Divider
200 mV 1/1
2V* 1/1
20V 1/100
200V 1/1000
1000V* 1/1000
200 mV 1/1
2V 1/10
20V 1/100
200V 1/1000
750V* 1/1000
Theory of Operation
Functional Description
Range of A/D Converter Input
-200 mV to +200 mV
-2V to +2V
-200 mV to +200 mV
-200 mV to +200 mV
-2V to + 2V (1V max. input)
0 to -200 mV
0 to -200 mV
0 to -200 mV
0 to -200 mV
0 to -2V (-0.75V max. input)
3
3-9