General Tools and Instruments GT310 User Manual

Page 14

CHECKING THE INTEGRITY OF A DIODE
OR THE CONTINUITY OF A CIRCUIT

Before checking a diode or checking for continuity, be sure to remove
power from the circuit under test.

Turn the rotary dial to the

Ω

position. With the symbol M

Ω

at the right

of the display, briefly press the Select/0-9 button once to call up the
diode symbol

Connect the red test lead to the anode (positive terminal) of the diode
to be tested, and the black test lead to its cathode (negative terminal).
Read the forward bias voltage value on the display. A typical silicon
diode has a forward bias voltage between 0.7 and 0.99V. A typical
germanium diode has a forward bias voltage between 0.3 and 0.36V.

A 0V reading in both directions indicates a shorted diode. An OL
reading indicates an open diode. In either case, the diode is defective
and should be replaced. An OL reading also may indicate that the
polarity of the test leads is reversed. This test can be used to
distinguish the anode and cathode of a diode.

To enter Continuity Check mode, briefly press the Select/0-9 button
once with the diode symbol

showing on the display. This will

change the diode symbol to the

Ω

unit. If the

icon is not visible at

the right of the display, activate the beeper by pressing the Buzzer
button.

In Continuity Check mode, the initial reading will be OL. Touch the test
leads to any two points in the circuit. If the resistance between the
points is <30

Ω

, the meter will produce a long beep.

MEASURING DC OR AC CURRENT

The circuit to be tested may not carry a voltage in excess of

1000VDC or 750VAC. Applying a current of >500 mA will blow the fuse
in the red test lead. To remove the fuse, unscrew the top of the red
lead. Replace the blown fuse with a fast-acting ceramic fuse with a
rating of 500mA/500V.

Turn the rotary dial to the uA or mA position, depending on the
expected amplitude. The unit uA or mA will appear at the right of the
display. The word AUTO will appear at the top left, indicating that the
meter is in Auto ranging mode.