Operation Manual

Model 2750 Multimeter/Switch System User’s Manual Basic DMM Operation 3-3
High energy circuit safety precautions
To optimize safety when measuring voltage in high energy distribution circuits, read and
use the directions in the following warning.
WARNING Dangerous arcs of an explosive nature in a high energy circuit can
cause severe personal injury or death. If the multimeter is connected to
a high energy circuit when set to a current range or low resistance
range the circuit is virtually shorted. Dangerous arcing can result even
when the multimeter is set to a voltage range if the minimum voltage
spacing is reduced in the external connections.
As described in the International Electrotechnical Commission (IEC)
Standard IEC 664, the Model 2750 is Installation Category I and signal
lines must not be directly connected to AC mains.
When making measurements in high energy circuits, use test leads that meet the following
requirements:
• Test leads should be fully insulated.
• Only use test leads that can be connected to the circuit (e.g., alligator clips, spade
lugs, etc.) for hands-off measurements.
• Do not use test leads that decrease voltage spacing. These diminish arc protection
and create a hazardous condition.
Use the following sequence when testing power circuits:
1. De-energize the circuit using the regular installed connect-disconnect device, for
example, by removing the device's power cord or by turning off the power switch.
2. Attach the test leads to the circuit under test. Use appropriate safety rated test leads
for this application. If over 42V, use double insulated test leads or add an additional
insulation barrier for the operator.
3. Set the multimeter to the proper function and range.
4. Energize the circuit using the installed connect-disconnect device and make mea-
surements without disconnecting the multimeter.
5. De-energize the circuit using the installed connect-disconnect device.
6. Disconnect the test leads from the circuit under test.
WARNING For the front panel inputs, the maximum common-mode voltage (volt-
age between INPUT LO and the chassis ground) is 500V peak. For a
switching module, the maximum common mode voltage is 300V.
Exceeding these values may cause a breakdown in insulation, creating
a shock hazard.
2750-900-01.book Page 3 Wednesday, August 3, 2011 7:56 AM