720A Operation and Maintenance Manual – Rev S – January 25, 2019
Page 18
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While not mandatory, it is also recommended that one perform a quick visual inspection
of the test leads/probes being used to locate any obvious damage. Damaged cables,
banana jacks, or probe/lead ends can negatively impact the validity and accuracy of
measurements.
Once the unit’s warm up period has elapsed, you may then connect your supplied
AMPTEC test leads/probes to the appropriate corresponding jacks on the unit’s front
panel. On any AMPTEC test lead/probe set, the red cable should connect to the unit’s
HI terminals while the black cable should connect to the unit’s LO terminals.
Next, select the desired range of measurement for the test you are completing. If the
resistance value of the part you are testing is unknown, select the 200 KΩ range.
If your
unit has autorange and you would like to enable this feature, select the “AUTO” button
on the unit’s front panel.
To complete bond testing measurements (see
Figure 8
), find a clean area on both the
part you need to test (meaning an area with no paint or coating) and the metal chassis
of your unit under test (UUT). Pointed probes (such as the AMPTEC OP-403) work best
on aluminum parts, as this material often has a thin coating that is a non-conductor.
Press and hold each probe with a steady hand – one on the part under test and one on
the metal chassis – and do not move the probes for 3 to 5 seconds. If using the
autorange function, the meter needs a little settling time to automatically determine
which range is best before displaying a resistance value. If your 720A meter does not
have an autorange function and the resistance value is unknown,
start on the 200 KΩ
range. Once a resistance reading is displayed on the screen, you can then select/move
to a lower range to decrease the resolution value until the desired range is met.
Resistance testing of singular parts/units can be completed much the same way, but
instead of using one probe/lead on the chassis and one on the part under test, both
probes/leads would be placed on the part under test. Depending on the circumstance,
the supplied AMPTEC OP-300 Kelvin clip leads may be more appropriate for use than
the supplied AMPTEC OP-403 mini spear probe set.
The 720A Digital Micro-Ohmmeter consumes little power and generates minimal heat. It
may be used in any area where the environment does not exceed the unit’s
specifications (see section B). When possible, avoid exposing the meter to extremes of
temperature, which will affect accuracy and warm up time. If using your unit in areas
with an extreme temperature, please see section B to determine the temperature
coefficient that will need to be applied to your measurements.
If you have any further questions on how to use your 720A meter, please contact
AMPTEC.
