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MODEL 8120-100A/110A STRAIN GAGE CONDITIONER OPERATION MANUAL
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1.0
Description
Model 8120-100A/110A Signal Conditioner/Amplifiers
are designed for use with strain gage transducers that
can operate with a dc excitation-amplification source.
They supply either a 5 volt or a 10 volt transducer
excitation, which can be selected through proper wiring
at the I/O connector on the rear panel. Remote sensing
techniques are used to regulate the excitation voltage at
the transducer. The excitation voltage is protected
against overloads and accidental short circuits.
The 8120 uses a CMOS chopper-stabilized differential
signal amplifier, which has over 100-megohms input
impedance per input line. The circuit guarantees
negligible drift with temperature variations or
component aging.
The 8120-100A/110A contains all necessary balancing,
gain, and calibration controls and conditions/amplifies
the applied input to a standard +/-5 volt dc analog
output level. Two analog outputs, both having a low-
pass cutoff frequency, one of 2 Hz and the other of 200
Hz are provided. The filtered outputs allow for
averaging of signals containing noise, or other
unwanted dynamic components, which are periodic in
nature.
The 8120-110A is similar to the 8120-100A except it
also contains a dedicated 4.5 digit LED display with a 3
Hz update rate. The resolution of the digital display is
1:5000 (0.02% F.S.). The display also has a selectable
decimal point, trick count multiplier, and a trailing inert
zero.
Calibration of the instrument, to the transducer, is made
through conventional shunt technique, using an
internally installed calibration resistor. Front panel
push button provides for calibration in the positive
direction. Positive direction calibration can be checked
by means of
Remote Cal
terminals on the instrument
I/O connector.
2.0
Installation and Cabling
Mounting
The 8120 Series Instruments can be operated as bench-
top units or they can be rack or panel mounted.
Dimensions for all three types of installations are
shown in Figure 4 of the manual. Panel cut-out
dimensions for mounting the 8120 are also shown in
Figure 4. Up to four 8120 Instruments can be mounted
in a 19 inch rack by using the 1 3/4 inch high Rack
Adaptor, (See B on Figure 1, page 7).
To panel mount a 8120, in a panel cut-out, please see
Item C on Figure 4, page 7, and Figure 5, on page 8,
for details. It is important, when panel mounting the
unit to
remove
the two spacer washers that are on the
securing screws of the rear panel I/O connector. This is
so that the printed-circuit board may move forward
about 1/8" during step (f).
(a) Remove the front panel by removing the two 2-56
x 3/8 flat head screws.
(b) Remove the front bezel by removing the four 6-32
x 5/8 fillister-head screws.
(c) Make the panel cut-out and drill the screw
clearance holes indicated in Figure 4.
(d) The front bezel can be used as a template to define
the rectangular cut-out and locate the clearance
holes.
(e) Hold the instrument enclosure behind the panel
and re-attach the front bezel to the enclosure from
the front of the panel with the four remaining
screws.
(f) Reinstall the front panel.
(g) Tighten the two securing screws of the rear panel
I/O connector to insure that the connector is seated
and that the conditioner printed-circuit board is
pushed fully forward so that the front-panel
screwdriver
adjustments
and
buttons
are
accessible. These screws give approximately 1/8
inch adjustment; consequently, this is the
maximum panel thickness, which should be used.
CAUTION:
Do not over tighten the connector
securing screws or resultant damage may occur to
the printed circuit board.
AC Power Connection
To protect operating personnel, the 8120 Series
Instruments are equipped with a three conductor power
cord. When the cord is plugged into the proper power
receptacle, the instrument is grounded. The offset pin
on the power cord plug is ground. To maintain the
safety ground, when operating the unit from a two
contact outlet, use a three prong to a two prong adaptor
and connect the green pigtail on the adaptor to a good
water pipe ground.
To prepare the instrument for operation, connect the
power cable to a 105-135 volt ac, 50-400 Hz power
