GW Instek GDM-9060 - Page 77

DUAL MEASUREMENT
77
Example
Vs = Voltage source
RLoad = Load under test
Rint = Current terminal total impedance containing
Rshunt + Fuse + Rline
Rline
+ Rline
Rline
When different current range for measurement is
selected, Rshunt will vary accordingly.
For example,
Vs = 10V, Rload = 10 Ω, Rint = total impedance
flowing through current terminal 0.5Ω
The theoretical value for current reading should be
= 1A in that the DMM internal resistor
Rint, which contains Shunt, Rline
Rline
, Rline
Rline
and Fuse,
will cause impact on the measuring reading.
The measured value is I =
= 0.952381 A.
Error (%) = * 100
This error is applicable to not only DC but AC
measurement, and the burden voltage, per varied
current measuring range, is generally within the range
of several hundreds mV.
DC Current
Range
Shunt
Burden Voltage
100 μA
100 Ω
<0.011 V
1 mA
100 Ω
<0.11 V
10 mA
1 Ω
<0.04 V
100 mA
1 Ω
<0.4 V
1 A
0.1 Ω
<0.7 V
3 A
0.1 Ω
<2 V
10 A
10m Ω
<0.5 V
The above table indicates the maximum burden voltage caused
by the maximum current within the applicable range.
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