Seaward IRT 1557 - Manual (Page 15)

IRT1557
Operating Instructions
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5.6 Measuring voltage
5.5.1 Rotate the rotary switch until the voltage test is
selected.
5.5.2 Connect the test probes to the circuit to be
measured.
If the voltage measured contains both ac and dc
components, the value of the largest component
is displayed.
5.6 Test ‘Lock’ function
5.6.1 When continuous insulation or continuity
resistance measurement is required, the TEST
key can be locked in the ON position to avoid the
need to press and hold the key.
5.6.2 To operate the LOCK function, press the TEST
key, then press the LOCK key, then release both
keys simultaneously.
5.6.3 When the LOCK function is active the lock icon is
shown on the display.