720A Operation and Maintenance Manual – Rev S – January 25, 2019
Page 15
13231 Rooster Springs Rd.,
Austin, TX 78737
T:
(512) 858-4045
E:
amptec.com
adapter to connect your 720A meter to your computer. Connection to this port from your
computer allows you to send commands directly to your 720A meter. For more
information on how to use the RS-232C function, see section D-7.
D-3.5 Fan, Fan Guard, and Air Intake
The fan guard (refer to item 5 within
Figure 4
on page 13) protects the unit’s internal fan
and prevents obstructions from the vent. It is important that you assist the fan by not
unnecessarily obstructing or covering the vent while your unit is on. Additionally, the unit
has seven (7) holes on the bottom plate that draw in outside air. These intake holes
work with the fan to cool the unit, and it is important that they are also not obstructed or
covered while operating your 720A. A unit that cannot properly intake air through the
bottom holes or expel heat through the vent may overheat, which can lead to less
accurate measurements.
D-3.6 DC Power Jack
This feature (refer to item 6 within
Figure 4
on page 13) is only present in the 720-BAT
battery powered version of the 720A meter. This DC power jack acts as a receiver for
the battery charger (P/N 720-DC) that comes with the unit. It is through this jack that the
unit receives power that charges its batteries. This DC power jack has a current rating
of 5A and a voltage rating of 12V. We do not recommend attempting to charge the unit’s
batteries with any charger not supplied by AMPTEC. If operating this unit from outside
of the U.S., please contact AMPTEC for assistance in purchasing a different variation of
charger or an outlet adaptor.
D-4 Battery Holder Design and Description
The battery powered version of the 720A Digital Micro-Ohmmeter has two battery
holders inside which are affixed to the bottom plate of the unit. Each battery holder is
made of a durable black plastic and houses 4 D cell NiMH batteries for a total of 8
batteries per unit (for more information on battery specifications see section B-3).
One safety feature the unit has is a temperature fuse that is installed on each battery
holder. This fuse ensures the batteries do not overheat and cause damage to the unit.
Another safety feature is the addition of a flame-retardant laminate cover plate to protect
the batteries from coming in contact with any leads on the PC board, which would in
turn short out the unit and prevent it from functioning properly.
Lastly, both battery holders are then sealed with a layer of durable fiberglass tape to
prevent any battery shifting, as well as to provide a final level of protection.
D-5 Test Lead Connections
The AMPTEC 720A meter test lead connection uses 4 banana jack terminals on its front
panel. These inputs are gold-plated and accept a variety of connections. Most
commonly, cables with a banana jack on one end may easily plug into the front of these
terminals. If you would like to use a different cable set that does not have banana jacks,
this is achievable by unscrewing the plastic that covers these jacks. This exposes a
horizontal hole through the gold-plated post which you can insert a bare wire into. Once
