High-Energy Circuit Safety Precautions; Power Circuit Test Procedure; Performance Considerations; Warmup Time - Keithley 3700A Series Reference Manual

Section 4: Basic DMM operation

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.
Dangerous arcs of an explosive nature in a high-energy circuit can cause severe personal
injury or death. If the Series 3700A 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 Series 3700A is set to a voltage range if the minimum voltage spacing is
reduced in the external connections.
As described in International Electrotechnical Commission (IEC) Standard IEC 60664, the
Series 3700A 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 (for example, alligator clips and spade
lugs) for hands-off measurements.
•
Do not use test leads that decrease voltage spacing. These diminish arc protection and create a
hazardous condition.

Power circuit test procedure

When testing power circuits:
1. Turn off power to the circuit using the regular installed connect-disconnect device. For example,
remove the device's power cord or turn 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 42 V, use double-insulated test leads or add an additional insulation barrier for
the operator.
3. Set the Series 3700A to the proper function and range.
4. Power the circuit using the installed connect-disconnect device and make measurements without
disconnecting the multimeter.
5. Remove power from the circuit using the installed connect-disconnect device.
6. Disconnect the test leads from the circuit under test.

Performance considerations

There are several settings and conditions that apply to all DMM measurements, as described in the
following sections.

Warmup time

After the Series 3700A is turned on, it must be allowed to warm up for at least two hours to allow the
internal temperature to stabilize. If the instrument has been exposed to extreme temperatures, allow
extra stabilization time.
4-2
Series 3700A System Switch/Multimeter Reference Manual
3700AS-901-01 Rev. D/June 2018