Fluke 1520 User Manual page 20

Using the LOCK Function to Measure Insulation Resistance
The LOCK function holds the test voltage on the probes. Use LOCK to make long duration
measurements without having to push and hold the TEST button.
To use the LOCK function:
1. Press the TEST button, then press the LOCK button, and then release both
simultaneously.
In this mode a potentially dangerous voltage is continuously applied to the
probes.
In this mode, if the probes are disconnected from the circuit, the Meter
cannot discharge any potentially dangerous capacitive voltages left on the
circuit.
In this mode the Meter cannot indicate if the circuit is live.
Ensure that the circuit is de-energized before connecting the test probes in
this mode.
2. Press LOCK or TEST to disengage the lock function.
W
Warning
Caution
MegOhmMeter
Using the Meter
15