PCB Piezotronics 8120G-400A User manual

Model 8120G-400A
Strain Gage Sensor Signal Conditioner
Installation and Operating Manual
For assistance with the operation of this product,
contact PCB Piezotronics, Inc.
Toll-free: 800-828-8840
24-hour SensorLine: 716-684-0001
Fax: [phone]
E-mail: [email protected]
Web: www.pcb.com

The information contained in this document supersedes all similar information that
may be found elsewhere in this manual.
Total Customer Satisfaction – PCB
Piezotronics guarantees Total Customer
Satisfaction. If, at any time, for any
reason, you are not completely satisfied
with any PCB product, PCB will repair,
replace, or exchange it at no charge. You
may also choose to have your purchase
price refunded in lieu of the repair,
replacement, or exchange of the product.
Service – Due to the sophisticated nature
of the sensors and associated
instrumentation provided by PCB
Piezotronics, user servicing or repair is
not recommended and, if attempted, may
void the factory warranty. Routine
maintenance, such as the cleaning of
electrical connectors, housings, and
mounting surfaces with solutions and
techniques that will not harm the
physical material of construction, is
acceptable. Caution should be observed
to insure that liquids are not permitted to
migrate into devices that are not
hermetically sealed. Such devices should
only be wiped with a dampened cloth
and never submerged or have liquids
poured upon them.
Repair – In the event that equipment
becomes damaged or ceases to operate,
arrangements should be made to return
the equipment to PCB Piezotronics for
repair. User servicing or repair is not
recommended and, if attempted, may
void the factory warranty.
Calibration – Routine calibration of
sensors and associated instrumentation is
recommended as this helps build
confidence in measurement accuracy and
acquired data. Equipment calibration
cycles are typically established by the
users own quality regimen. When in
doubt about a calibration cycle, a good
“rule of thumb” is to recalibrate on an
annual basis. It is also good practice to
recalibrate after exposure to any severe
temperature extreme, shock, load, or
other environmental influence, or prior
to any critical test.
PCB Piezotronics maintains an ISO-
9001 certified metrology laboratory and
offers calibration services, which are
accredited by A2LA to ISO/IEC 17025,
with full traceablility to N.I.S.T. In
addition to the normally supplied
calibration, special testing is also
available, such as: sensitivity at elevated
or cryogenic temperatures, phase
response, extended high or low
frequency response, extended range, leak
testing, hydrostatic pressure testing, and
others. For information on standard
recalibration services or special testing,
contact your local PCB Piezotronics
distributor, sales representative, or
factory customer service representative.
Returning Equipment – Following
these procedures will insure that your
returned materials are handled in the
most expedient manner. Before returning
any equipment to PCB Piezotronics,
contact your local distributor, sales
representative, or factory customer
service representative to obtain a Return
Warranty, Service, Repair, and
Return Policies and Instructions

Materials Authorization (RMA)
Number. This RMA number should be
clearly marked on the outside of all
package(s) and on the packing list(s)
accompanying the shipment. A detailed
account of the nature of the problem(s)
being experienced with the equipment
should also be included inside the
package(s) containing any returned
materials.
A Purchase Order, included with the
returned materials, will expedite the
turn-around of serviced equipment. It is
recommended to include authorization
on the Purchase Order for PCB to
proceed with any repairs, as long as they
do not exceed 50% of the replacement
cost of the returned item(s). PCB will
provide a price quotation or replacement
recommendation for any item whose
repair costs would exceed 50% of
replacement cost, or any item that is not
economically feasible to repair. For
routine calibration services, the Purchase
Order should include authorization to
proceed and return at current pricing,
which can be obtained from a factory
customer service representative.
Warranty – All equipment and repair
services provided by PCB Piezotronics,
Inc. are covered by a limited warranty
against defective material and
workmanship for a period of one year
from date of original purchase. Contact
PCB for a complete statement of our
warranty. Expendable items, such as
batteries and mounting hardware, are not
covered by warranty. Mechanical
damage to equipment due to improper
use is not covered by warranty.
Electronic circuitry failure caused by the
introduction of unregulated or improper
excitation power or electrostatic
discharge is not covered by warranty.
Contact Information – International
customers should direct all inquiries to
their local distributor or sales office. A
complete list of distributors and offices
can be found at www.pcb.com.
Customers within the United States may
contact their local sales representative or
a factory customer service
representative. A complete list of sales
representatives can be found at
www.pcb.com. Toll-free telephone
numbers for a factory customer service
representative, in the division
responsible for this product, can be
found on the title page at the front of this
manual. Our ship to address and general
contact numbers are:
PCB Piezotronics, Inc.
3425 Walden Ave.
Depew, NY 14043 USA
Toll-free: [phone]
24-hour SensorLineSM: [phone]
Website: www.pcb.com
E-mail: [email protected]
DOCUMENT NUMBER: 21354
DOCUMENT REVISION: B
ECN: 17900

i
Table of Contents
Section 1.0 Description Page 1
Section 2.0 Installation and Cabling Page 1
Section 3.0 Calibration Page 7
Section 4.0 Calibration of PCB Rotary Transformer Torque Sensors Page 8
Section 5.0 Troubleshooting Page 9
Reference Figures
Figure 1 Bench Mounting Clearance Dimensions Page 2
Figure 2 Panel Mounting Cut-Out Dimensions Page 2
Figure 3 Panel Mount Assembly Page 3
Figure 4 Rack Mounting Dimensions Page 4
Figure 5 4200 Series Cabling Page 5
Figure 6 182-015A Connector Pin-Out Page 5
Figure 7 4-Conductor Cabling Page 5
Figure 8 4100 Series Cabling Page 5
Figure 9 8-Conductor Cabling Page 5
Figure 10 Remote Calibration Methods Page 6
Figure 11 Master / Slave Connections Page 6
Figure 12 Front Panel Descriptions Page 11
Figure 13 Rear Panel Descriptions Page 12
MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
MANUAL NUMBER: 18222
REVISION: B
ECO NUMBER: 37012

MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
1.0 DESCRIPTION
Model 8120-400A Transducer Signal
Conditioner/Amplifier is designed for use with
resistance strain gage transducers that require
an AC excitation-amplification source. It
supplies a 3.28 kHz frequency, precision
amplitude-regulated excitation, which is
remotely sensed to the transducer. The
instrument uses a phase-sensitive carrier
amplifier-demodulator design so that both
direction and magnitude of the applied force are
determined. The 8120-400A contains all
necessary balancing and calibration controls
and condition/amplify the applied input to a
standard ±5 volt DC analog output level. Two
analog outputs, both having low-pass cutoff
frequencies, one of 2 Hz and the other of 400
Hz, are provided. The filtered outputs provide
for averaging of signals containing noise or
other unwanted dynamic components that are
periodic in nature.
The 8120-400A is used in applications
involving transformer coupling of the strain
gage bridge (rotary transformer coupled torque
sensors for example), and in applications that
require a high sensitivity (amplification) with
optimum "signal to noise" characteristics.
Carrier amplifiers offer higher sensitivity than
comparable DC-excited bridge amplifiers, and
since they respond only to the modulated carrier
frequency, they reject certain extraneous
voltages that cause interference with DC-
excited bridge instruments.
Note: If you have a PCB rotary transformer
torque sensor, please refer to Section 3 of this
manual, or to either the 4100 Series Rotary
Transformer Torque Sensor Manual (PCB
Manual #18227), or the 4200 Series Rotary
Transformer Torque Sensor Manual (PCB
Manual #18228), for calibration procedures.
Calibration of the instrument is made through
conventional shunt technique, using an
internally installed calibration resistor, or an
external shunt calibration reference, such as our
Model 8113A or 8113-105A Shunt Calibration
References. Front panel calibration buttons
provide for calibration in both the positive and
negative directions. An internal symmetry
control provides independent adjustment of the
negative direction sensitivity for transducers
that do not have symmetrical positive and
negative slope characteristics. Positive
direction calibration can be checked by means
of REMOTE CAL terminals on the instrument
I/O connector.
The 8120-400A Strain Gage Conditioner is also
available in two additional forms. The 8120-
410A is similar to the 8120-400A except it also
contains a dedicated 4.5 digit LED display with
a 3Hz update rate. The resolution of the digital
display is 1:5000 (0.02% FS). The display also
has a selectable decimal point, trick count
multiplier, and a trailing inert zero. For more
information on instruments with digital display,
refer to PCB Manual #27259. The Model
8120-430A contains a Limit section (in addition
to a Digital Indicator) that provides
High/OK/Low indications and outputs. Refer to
PCB Manual #19479 for more information.
The Digital Indicator and Limit features are
standard to all 8120 Series Instruments.
2.0 INSTALLATION AND CABLING
The following paragraphs provide the
instructions for instrument installation and
cabling.
Mounting
The 8120 Series Instruments can be operated as
bench-top units or they can be rack or panel
mounted. Clearance dimensions for a bench-
mounted instrument are given in Figure 1 and
cut-out dimensions for panel mounting are
shown in Figure 2.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Figure 1 – Bench Mounting Clearance Dimensions
Figure 2 – Panel Mounting Cut-Out Dimensions
To panel mount an instrument, proceed as follows, referring to Figure 3.
Important: The unit is shipped with two spacer washers on the securing screws of the rear-panel I/O
connector. When panel-mounting the unit, you must remove these washers so that the printed circuit
board may move forward about 1/8" during Step (6).
1. Remove the front panel by removing the two #2-56 x 3/8” flat-head screws.
2. Remove the front bezel by removing the four #6-32 x 5/8” fillister-head screws.
3. Make the panel cut-out and drill the screw clearance holes indicated in Figure 2. The front
bezel can be used as a template to define the rectangular cut-out and locate the clearance holes.
4. 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.
5. Reinstall the front panel.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
6. Tighten the two securing screws of the rear panel I/O connector to ensure 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 that should be used.
Caution: Do not over tighten the connector securing screws or resultant damage may occur to the
printed-circuit board.
8120 SERIES
MODULE
Figure 3 – Panel Mount Assembly
To rack mount an instrument, refer to Figure 4. Up to four 8120 Series Instruments can be mounted in a
19-inch rack using the 1.75-inch high Model 8171A Rack Adaptor.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Figure 4 – Rack Mounting Dimensions
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 appropriate receptacle, the
instrument is grounded. The offset pin on the
power cord is ground. To maintain the safety
ground when operating the unit from a two-
contact outlet, use a three-prong to two-prong
adaptor and connect the green pigtail on the
adaptor to ground.
To prepare the instrument for operation,
connect the power cable to a 105-135 volt AC,
50-400 Hz power source. The instrument can
use up to 5 watts of power.
Calibration Resistor
If a fixed resistor is shunted across one arm of a
strain gage Wheatstone Bridge, it produces an
unbalance equivalent to that of a particular
value of mechanical input. If this Equivalent
Input value is accurately known, it can be used
as a reference point for shunt calibration of the
system. Upon completion of installation of the
transducer and its associated cabling, the user
can:
1. Perform an overall dead weight calibration
using a precisely known value of
mechanical input. Shunt calibration data
then can be collected by means of the
installed calibration resistor for
convenience in subsequent checking.
2. Replace the installed calibration resistor
with one (or an equivalent resistance value)
supplied by the transducer manufacturer to
achieve a precisely known Equivalent Input
allowing the instrument sensitivity to be
adjusted correctly.
3. Determine the Equivalent Input value for
the installed calibration resistor, knowing
the transducer sensitivity, and adjust the
instrument sensitivity accordingly.
4. A precision 59KΩcalibration resistor is
installed in the 8120 at the factory. The
installed resistor can usually be used even
though the transducer calibration data
mentions some other resistance value. In
Section 3 of this manual, the techniques
described above are demonstrated. If,
however, the installed value of calibration
resistor is not appropriate for the transducer
and measurement range to be used, the
59KΩresistor should be replaced at this
time. The calibration resistor is mounted
on solder terminals located at the front edge
of the conditioner printed-circuit board in
the instrument. It can be accessed by
removing the front panel.
Note: PCB 4200 Series Rotary Transformer
Torque Transducers are supplied with the
appropriate calibration resistor integral to the
transducer. When this type of transducer is
used with the 8120-400A, it is not necessary to
remove the 59KΩresistor internal to the
instrument. The calibration resistor can be
appropriately connected to the 8120-400A
calibration circuit via the transducer cabling.
Refer to Figure 5 and the following section.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Figure 5 – PCB 4200 Series Cabling
Transducer Cabling
Cabling to the transducer is accomplished via
the supplied instrument I/O connector (PCB
Model 182-015A). The I/O connector pin
numbers and functions are given in Figure 6.
Rear View
PIN PIN
1 +EXCITATION A +SENSE
2 -EXCITATION B -SENSE
3 +SIGNAL INPUT C CALIBRATION SENSE
4 - SIGNAL INPUT D OSC. DISABLE
5 SIGNAL COMMON E TRANSDUCER CABLE SHIELD
6 OSC. INPUT F OSC. OUTPUT
7 NC H ANALOG OUTPUT
8 REMOTE CALIBRATION J ANALOG OUTPUT
9 OUTPUT SHIELD K NC
10 OUTPUT SIGNAL COMMON L NC
Figure 6 – 182-015A Pin Out
Transducer cabling should take the form of a 4,
6, or 8-wire cable configuration. The 4-wire
configuration, shown in Figure 7, should be
used when overall deadweight calibration is the
method used and the required cable length is
less than 20 feet.
Figure 7 – 4 Conductor Cabling
The 6-wire configuration, shown in Figure 8,
should be used when the instrument is to be
calibrated by achieving a precisely known
Equivalent Input value through the use of a
shunt calibration resistor supplied by the
transducer manufacturer and when the required
cable length is less than 20 feet.
Figure 8 – PCB 4100 Series Cabling
The 8-wire configuration, shown in Figure 9,
should be used with cable lengths longer than
20 feet since the excitation voltage is sensed
and regulated at the transducer and optimum
shunt calibration can be achieved.
Figure 9 – 8 Conductor Cabling
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Remote Calibration Check
The instrument can be placed in the calibration
mode (positive realm only) by shorting pins 5
(Signal Common) and 8 (Remote Cal) of the
rear-panel I/O connector. Figure 10 indicates
three methods of remotely entering the
calibration mode (external switch, transistor, or
TTL source).
Figure 10 – Remote Calibration Methods
Master/Slave Connections
When more than one 8120-400A (or a
combination of AC Carrier Conditioners) is
being used in a measurement setup (instruments
are continuously mounted or the transducer
cabling is in a common conduit or raceway),
beat frequencies may be produced from the 3-
kHz oscillators used in the instruments to power
the transducer(s) excitation. To prevent beat
frequencies from occurring, one unit can be
designated the Master, and the other units can
be driven from the Master oscillator. The
remaining units are designated as Slave
instruments. To connect as Master/Slave units,
refer to Figure 11.
Figure 11 – Master/Slave Connections
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Analog Outputs
Two analog outputs are simultaneously
available at the instrument I/O connector, with
each output having a different passband: DC to
2 Hz and DC to 400 Hz. The cutoff frequencies
are achieved with active low-pass filters. When
the DC to 2 Hz output is used, a trade off is
made between noise elimination and increased
time-to-answer, or slew time. Each output has a
60db rolloff a decade from the cutoff
frequency.
The filter characteristics are given by
the following equations:
3.0 CALIBRATION
This section contains the instructions for
calibrating the 8120-400A. Included is a
functional description of the instrument front-
panel (see Figure 12). To perform calibration,
proceed as follows.
1. Turn power ON by placing the rear-panel
slide switch in the ON position. The front-
panel indicator should light to indicate the
application of AC power. Allow 5 minutes
of warm-up for stabilization of transducer
characteristics.
2. Make sure the transducer is unloaded and is
free from locked in torque or load by
releasing one end. Zero the output reading
with the Fine and Coarse R balance
controls.
3. Press the NULL button and adjust the C
BALANCE control to obtain the minimum
(least positive, most negative) output
reading. In some instances, an integral
digital indicator will be used to display the
conditioner output (Model 8120-410A or
8120-430A). When only the conditioner is
supplied (8120-400A), an external indicator
must be used to monitor the conditioner
output. Release the NULL button. This
step need only be performed one time for
any transducer/cable combination.
Dead Weight Calibration
1. Load the transducer in the positive direction
with a convenient dead weight value that is
greater than one half of full scale.
The following step is only for Rotary
Transformer Transducers. If not using a
Rotary Transformer Transducers, skip to
step 2.
1a. Remove the 8120’s front panel (one
small flat-head screw near each edge) to
access the SYMMETRY and PHASE
adjustments. Adjust the PHASE control
(the one to the extreme right), until a
maximum output value is obtained. Once
set for your transducer, this PHASE
adjustment step need not be repeated unless
a great change in cable length or
capacitance is required.
2. Adjust the Coarse and Fine SPAN controls
until the output value equals the dead
weight value. Remove the dead weight, and
then press the +CAL button, noting the
indicator reading obtained. In future
calibrations, you need only press the +CAL
button and adjust the SPAN controls until
you obtain the previously recorded dead
weight reading.
3. If the transducer is to be also used in the
negative direction, load the transducer in
the negative direction with the same dead
weight value as used in step (1) and
confirm that the dead weight reading
obtained is the same as that of step (1). If
not, see steps (4).
4. An internal SYMMETRY adjustment is
provided to compensate for transducers that
do not have symmetrical sensitivity
characteristics. This adjustment is factory
set assuming symmetrical characteristics. If
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
step (3) indicates that a field adjustment is
necessary, proceed as follows:
Remove the front panel by removing
the two #2-56 flat head screws to obtain
access to the SYMMETRY adjustment.
With the transducer loaded as in step
(3), adjust the SYMMETRY control
(just to the right of the –CAL button) to
obtain a dead weight reading equal to
that obtained in step (3).
Shunt Resistor Calibration
If dead weight calibration is not practical
and the transducer manufacturer has
supplied a calibration resistor (or resistor
value), install the recommended calibration
resistor in place of the installed 59KΩ
resistor as discussed in Section 2. If you
purchased a complete system from PCB
Piezotronics, this step may not be
necessary. Please consult our factory.
1. Complete steps (2) and (3). Now press
the +CAL button and adjust the PHASE
control until a maximum output reading
is obtained. Once set for your
transducer, this PHASE adjustment step
need not be repeated unless a great
change in cable length or capacitance
occurs.
2. Next adjust the SPAN controls until the
instrument output is equal to the
Equivalent Input value simulated by the
installed resistor. Now release the
+CAL button.
3. If a negative Equivalent Input value is
also provided (as in the case of PCS’s
calibration sheet), press the –CAL
pushbutton and confirm that the
negative value can also be obtained
with the same setting of the Coarse and
Fine controls. If not, adjust the
Symmetry control to obtain the
negative Equivalent Input value.
4.0 CALIBRATION OF PCB ROTARY
TRANSFORMER TORQUE SENSORS
Shunt calibration of the Model 4100 Torque
Sensor Series is done utilizing the PCB Model
8113-105A or 8113A Calibration Reference
Box.
Preparation
Do not follow the procedure, in Section 2 for
replacement of the shunt calibration resistor
since a calibration resistor is included with each
PCB Rotary Transformer Torque Sensor. It
should already be installed in the Calibration
Reference Box Model 8113-105A or 8113A.
Calibration with 8113-105A Calibration
Reference Box
A Model 8113-105A Calibration Reference
Box is shipped with each PCB 4100 Series
rotary torque sensor and contains a precision
shunt calibration resistor for performing
calibration of the 8120-400A/410A instrument.
The box mounts directly on the edge connector
at the rear panel. It is activated with a DC
powered internal relay. A 5 VDC excitation
must be provided in series with a remote ON-
OFF switch in order to activate the relay to the
ON position. The internal resistor of the 8120-
400A/410A is bypassed when using a Model
8113-105A reference box.
Calibration Procedure
Both the transducer cable and 8113-105A
reference box should always be connected to
the 8120-400A/410A instrument.
1. With the relay OFF, zero the output reading
with the Coarse and Fine R balance
controls.
2. Turn the relay ON.
3. Zero the output again with the Coarse and
Fine R balance controls.
4. Push the +CAL button and adjust the SPAN
such that the reading matches the +CAL
value on the transducer calibration sheet.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
5. Release +CAL and check zero; adjust if
necessary. Check +CAL and adjust if
necessary. Repeat steps (4) and (5) until
zero and span are correct.
6. Push the -CAL button and adjust the
SYMMETRY pot located behind the front
panel to the right of the –CAL button, until
the reading matches the –CAL value on the
transducer calibration sheet.
7. Turn the relay OFF.
8. Check and adjust zero per step (1). No
further adjustment is required with the relay
ON, even if the zero changed from step (1).
Calibration with 8113A Calibration
Reference Box
The Model 8113A Calibration Reference Box
may be used in some cases and contains a
precision star bridge and two position rotary
switch that allows the user to switch to either
CAL mode or RUN mode.
Calibration Procedure
1. Switch the 8113A to the RUN position and
zero the output reading with the Coarse and
Fine R balance control.
2. Switch the 8113A to the CAL position.
3. Zero the output again with the Coarse and
Fine R balance controls.
4. Push the +CAL button and adjust the SPAN
such that the reading matches the +CAL
value on the transducer calibration sheet.
5. Release +CAL and check zero; adjust if
necessary. Check +CAL and adjust if
necessary. Repeat steps (4) and (5) until
zero and span are correct.
6. Push the -CAL button and adjust the
SYMMETRY pot, located behind the front
panel to the right of the –CAL button, until
the reading matches the –CAL value on the
transducer calibration sheet.
7. Switch the 8113A to the RUN position and
check the instrument zero and adjust per
step (1).
8. No further adjustment is required with the
8113A in the CAL position, even if the zero
changed from step (1).
5.0 TROUBLESHOOTING
If the instrument is suspected of faulty
operation, observe the following steps:
1. If the unit is totally inoperable (front panel
power indicator does not light), check the
primary power fuse (F1) located on the
standup board that forms the power cord
connection point. If the fuse is blown,
replace it with a 0.50 ampere fuse of
equivalent manufacture. Before reapplying
power, visually inspect the power cord and
the input power connections for anything
that could have caused the overload.
2. The inability to balance correctly where the
instrument output reads totally off-scale and
the balance controls have no authority can
very likely be the result of a damaged, or
defective transducer or cable. This
possibility can be confirmed, or eliminated,
by substituting a transducer and or cable
known to be in good condition or by
simulating a balanced transducer. PCB
supplies a simple Star Bridge consisting of
four precision resistors mounted on a
female circuit board edge connector that is
supplied in the shipping box. Use the Star
Bridge by plugging it into the back of the
8120 as if it were a transducer and
interconnect cable and proceed with a
calibration again. If the instrument works
okay and a satisfactory calibration is
achieved, then the transducer or cable is
faulty. If a satisfactory calibration is not
achieved, then the instrument is at fault.
3. Step (2) above is to be used only to verify
instrument operation. Calibration
instructions, found in Section 3 of this
manual, must be completed before the
Instrument and Transducer are used.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Note: The user can contact the factory for
assistance. See the front page of this manual
for phone and fax numbers for the factory.
10

MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Figure 12 – Front Panel
R and C Balance Controls
These controls are used to set the output to zero when the transducer is unloaded.
NULL Pushbutton
This pushbutton is pressed when nulling the transducer bridge with the R and C Balance
controls. It provides for non-synchronous demodulation of the carrier for balancing
purposes. After a minimum reading is obtained on the display device by adjusting the C
control, the push-button is released and the output is zeroed using the R controls.
SPAN Controls
The Coarse and Fine SPAN controls are used to set the output to the dead weight value
when dead weight calibration is used. They can also be used to set the output to the
Equivalent Input value when the CAL (+ or -) button is pressed.
CAL Pushbuttons
The +/–CAL pushbuttons provide for shunt calibration in the positive and negative
directions, respectively. They are used in conjunction with the SPAN controls to
calibrate the instrument. When both positive and negative direction calibration is
required, the +CAL button is used in conjunction with the SPAN controls and the –CAL
button is used with the internal SYMMETRY adjustment.
PHASE Control
The PHASE Control is used to give maximum output possible when a transducer and
cable are connected to the instrument. The pot is accessed by removing the front panel.
It is located to the extreme right.
SYMMETRY Control
The SYMMETRY Control is used to compensate for transducers that do not have
symmetrical sensitivity characteristics in compression/tension for load cells, or
CW/CCW rotation for torque sensors. The pot is accessed by removing the front panel.
It is located to the right of the -CAL button.
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MODEL 8120-400A AC SIGNAL CONDITIONER OPERATION MANUAL
Figure 13 – Rear Panel
Decimal Point / Dummy Zero Switches
These switches, located in the upper right corner of the panel, place the decimal point in
its proper place for the measurement range. Moving one of the switches places the
decimal point at the selected position on the front panel display. Switching the
rightmost switch "ON" causes an inert zero to be displayed.
Scale Selection Buttons
These pushbuttons control the range shown on the front panel display. For instance, if
both pushbuttons are left fully extended rearwards, the full-scale display will read 5000.
Pushing the left button in and leaving the right button extended out will cause the full
scale display to be a maximum of 20000.
Input Power
The input power receptacle and the power ON/OFF switch are at the left side of the rear
panel.
I/O Connector Board
The circuit board connector, marked P1, supplies the total interface to the transducer.
See Section 2 for proper cable circuitry. Additional cable diagrams are shown in each
PCB Transducer manual.
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