AMMETERS
Test Instruments & Measuring Devices
Find: 1.
accuracy
2.
%loading error
3.
true current
4.
measured current
1.
KA
R
Ro
Rm
KA
2000
2000
400
KA
0.833 or 83.3%
2.
% loading error
(1
KA)(100%)
% loading error
(1
0.833)(100%)
% loading error
16.7%
3.
Io
V
Ro
20
2000
Io
0.01A or 10mA
4.
Iw
V
Ro
Rm
20
2000
400
Iw
8.33x103A or 8.33mA
An ammeter with a full scale Im can be shunted with a resistor RSH in order to measure currents
in excess of Im (Figure 8). The reason for shunting an ammeter is to extend the range of the
ammeter and, thereby, measure currents higher than the original full scale value.
ES-14
Page 12
Rev. 0
