3. CALIBRATION
Calibration of the IL70A
is
accomplished by the conventional shunt technique, using an internally
installed calibration resistor, or via the "dead-weight" method.
Calibration Resistor.
If a fixed resistor is shunted across one arm of a strain gage 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:
Perform an overall dead weight calibration using a precisely known value
of mechanical input. The calibration can then be transferred to the installed
calibration resistor for convenience in subsequent checking.
Use an external shunt resistor, please refer to the notes on page one of this manual. T
he
installed calibration resistor
is typically
supplied by the transducer manufacturer
or is
referenced on the calbiraiton sheet that accompanies the tranducer. Using a known shunt
resistorance can
achieve a precisely known Equivalent Input allowing the instrument
sensitivity to be adjusted correctly.
Note, this shunt resistor may reside in the transducer
itself and is accessed via the input pins of the sensor.
D
etermine the Equivalent Input value for the
internally
installed
59K
calibration resistor,
knowing the transducer sensitivity, and adjust the instrument sensitivity accordingly.
Place the
jumper on the IL70A to "INT" to enable the 59K Ohm resistor.
A one percent, 59-kilohm calibration resistor is installed in the IL70A at the factory. The installed
resistor can usually be used even though the transducer calibration data mentions some
other resistance value. In Section 4 of this manual, the techniques described above are
demonstrated. If, however, the installed value of calibration resistor is not appropriate
for the transducer and
the
measurement range to be used,
an
external "EXT" shunt
resistor
should be
installed
. The
external
calibration resistor is
installed
from the "CAL Sense"
terminal
to either the + Signal or - Signal teminals depending on your polarity direction
when using the provided "shunt" switch
.
Note:
A variety of DC Load Cells and Slip Ring
Torque Transducers are supplied with the appropriate calibration resistor integral to the
transducer. When this type of transducer is used it will be necessary to place
the jumper in
"EXT" and connect the "Cal Sense" line to the appropiate pin on the transducer.
(1)
(2)
(3)
Calibration IL70A.3
This section contains the instructions for calibrating the IL70A. Included is a functional
description of the instrument front-panel (see Figure 2). To perform calibration, proceed
as follows with the sensor or calibration standard connected.
Turn power ON to the IL70A DC Power input terminal (11 to 28 Vdc input) The front-
panel indicator should light green to indicate the application of DC power. Allow 10
minutes of warmup for stabilization of transducer characteristics.
(a)
the Coarse and Fine SPAN controls. If not, adjust the Symmetry control
to obtain the negative Equivalent Input value.
If dead weight calibration is not practical and the transducer calibration
data is unknown, the Equivalent Input value for the factory-installed
calibration resistor can be approximated
mv/v sensitivity rating of the transducer
known.
as follows, assuming that
and the bridge resistance
the
are
13
(m)
the Coarse and Fine SPAN controls. If not, adjust the Symmetry control
to obtain the negative Equivalent Input value.
If dead weight calibration is not practical and the transducer calibration
data is unknown, the Equivalent Input value for the factory-installed
calibration resistor can be approximated
mv/v sensitivity rating of the transducer
known.
as follows, assuming that
and the bridge resistance
the
are
13
(m)
recommended calibration resistor.
the Coarse and Fine SPAN controls. If not, adjust the Symmetry control
to obtain the negative Equivalent Input value.
If dead weight calibration is not practical and the transducer calibration
data is unknown, the Equivalent Input value for the factory-installed
calibration resistor can be approximated
mv/v sensitivity rating of the transducer
known.
as follows, assuming that
and the bridge resistance
the
are
13
(m)
Calibration 5M70.3
DC Strain Gage Conditoner
Module
IL70A
