Guard Terminal Use - Fluke 1550C Manual Del Usurario

1550C/1555
Users Manual
To charge the battery with the ac power supply:
1. Turn the Tester off.
2. Disconnect the test leads from the Tester.
3. Move the safety shutter to access the power supply connection.
4. Connect the ac power cord to the IEC ac power socket on the Tester.
5. Connect the other end of the power cord to an ac power supply. See
"General Specifications" for ac charger input specifications.
The LCD displays CHARGING. Downloading is possible when the
Tester is in Charging mode.

Guard Terminal Use

Insulation resistance is measured between the (
connections. The Guard terminal (G) is at the same potential as the
negative (−) terminal but is not in the measurement path.
For most tests, only two test leads are used. Connect the positive (+) and
negative (−) test leads to the corresponding inputs on the Tester. Connect the
test lead probes to the circuit under test. The Guard (G) terminal is left
unconnected.
For the best accuracy when you measure very high resistances, use three-wire
measurements and the Guard terminal. The Guard terminal is at the same
potential as the negative (−) terminal, and can be used to prevent surface
leakage or other unwanted leakage currents from degrading the accuracy of the
insulation resistance measurement.
Figure 6 shows how to measure the resistance from one of the conductors to
the outer shield. In this case, there is a leakage current along the surface of the
inner insulation near the cables end. This leakage adds to the current that the
negative terminal senses, and causes the Tester to read a lower resistance than
it should.
12
Note
+
) and (
−
) output