PRODUCT SAFETY SOLUTIONS
© 2017 Educated Design & Development, Inc. All rights reserved. Rev C
Page 11 of 19
OPERATING INSTRUCTIONS:
This chapter explains the proper use of the LT-952HC. This includes instructions on how to perform
leakage measurements through the product under test’s power cord grounding conductor and measuring
leakage current from surface to ground or neutral and between surfaces. All of these tests generally need
to be run to test compliance with IEC60950. As such, they assume the product is completely isolated from
ground. Finally, this chapter will show how to measure leakage current in field-testing situations where the
product cannot be isolated from ground.
For these examples, assume that the product under test is a 120 Volt cord-connected piece of equipment
that is being tested for compliance. Please refer to
IEC60950
for complete testing specifics.
Measuring Through the D.U.T. Power Cord Ground
1. Isolate the product under test from ground. This can be accomplished by placing the product on a rubber
pad or other suitable insulator. This may also include disconnecting any accessory cables connected to the
product under test (i.e. a shielded monitor or printer cable).
2. To verify that there are no other grounds to the equipment under test, connect an ohmmeter between the
ground pin on the product under test and the power system ground. Readings of close to 0 Ohms indicate
the presence of an extraneous ground that needs to be removed. This step can probably be omitted for
simple test setups. The only penalty for an extraneous ground may be a blown meter fuse in the LT-
952HC.
3. Secure the work area so that you or another person cannot accidentally come into contact with the
product during the test. Since the product ground is disconnected while the Ground switch is toggled
OPEN, the product under test poses a potential shock hazard.
4. Set the controls on the LT-952HC as follows:
Voltage selector
115
Power
OFF
Neutral
CLOSED
Line
FORWARD
Meter Connection
D.U.T. GROUND
Range
20mA
5. Connect the product under test to the front panel receptacle. Make sure that the product under test’s
power switch is ON.
6. Turn the Power switch of the LT-952HC to ON. Observe that the leakage indicated on the LT-952HC is
ZERO. This is normal as the leakage current is flowing through the still connected product ground.
7. To measure leakage, depress and hold the Ground switch to the OPEN position. Within a few seconds,
the display on the LT-952HC should settle to the final leakage current value. If the displayed result is less
than 20mA, change the Range switch to the 2mA position.