5
1. INTRODUCTION
The Simpson Model 229-2 is a special purpose AC milliammeter designed to
measure hazardous leakage current from electrical appliances and other
power line operated equipment. A three-wire grounding power cord prevents
shock hazard by grounding the metal parts of the appliance; the grounding
connection, however, is subject to abuse and not always reliable or, some-
times, nonexistent or even defeated by the user (a two-wire extension cord,
for example). Leakage current is therefore measured with the grounding
connection open-circuited and is required to be within a specified limit for
shock prevention.
Leakage current (as it relates to a shock hazard), is the result of resistance
and capacitance between internal supply circuits and external parts acces-
sible to an operator, which may flow through the operator’s body to an earth
ground and cause electric shock. Although the appliances are energized by
a 60 Hz power line circuit, some may have solid-state control circuits which
generate higher frequency currents and may contribute to the leakage cur-
rent. The human body, however, has a decreasing sensitivity to the sensation
of electric shock as the frequency increases. The current ranges of the 229-
2 are compensated to indicate a decreasing value of current with an increase
in frequency in accordance with the perceptibility of the human body to shock.
The meter will have a constant indication for leakage current of 60 Hz and 20
kHz for the same degree of shock.
The 229-2 is designed only for measuring leakage current of appliances oper-
ating from 120 or 240 power line circuits. The current ranges of the 229-2 have
an insertion impedance of 1500 ohms, resistive with a parallel capacitance of
0.15
F. The meter indicates 1.1 times the average of the full-wave rectified
composite waveform of voltage across the 1500 ohm resistor. The 1500 resis-
tance simulates the resistance of the human body and the capacitance com-
pensates the meter indication to correspond with the decreasing sensitivity of
the body to shock at increasing frequency. See Figure 1 on page 3.
OFF
BATT TEST
300 VAC
DESIGNED TO MEET USA STANDARD C101.1 FOR LEAKAGE CURRENT TESTERS
1
2
3
4
5
6
7
8
9
10
.5
1
1.5
2
2.5
3
mA
mA
50
25
1
00
5
0
150
7
5
20
0
100
250
125
300
150
VAC
VAC
mA
OK
m
A
R
E
P
L
A
C
E
B
A
T
T
E
R
Y
B
A
T
T
E
R
Y
150 VAC
GROUND
MODEL 229-2
.3mA
1mA
3mA
10mA
A.C. LEAKAGE CURRENT TESTER
SHORT TEST
S
H
O
R
T
0
0
0
0
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