Hardy ANY-WEIGH Bench Scales - Manual (Page 33)

Chapter 6 - Calibration
6-5
volt (of transducer excitation) will be represented by
the 4-20 mA output range.
The gain can be adjusted from 3 mV input per volt of
excitation to as high as 0.8 mV input per volt of exci-
tation. This broad range of sensitivity allows for the
wide variation in transducer range that remains after
dead load compensation is subtracted by the Coarse
Zero adjustment.
Calibration
Procedures
NOTE: The measuring instruments used in the following pro-
cess must be designed so the test leads are isolated
from ground. These are either “floating” and/or
“isolated” and/or “differential” types.
NOTE: Insertion of any measuring device, or voltage drop-
ping resistor for a measuring device, in the output/
power loop requires that the power supply voltage be
high enough to supply the extra voltage.
Step 1. Remove all weights from the scale. Allow
dead load to remain. If dead load is coun-
terbalanced, also allow counterbalancing
to remain.
Step 2. Install a millimeter, in series, into the out-
put/power loop of the scale. If a voltmeter
is to be used for measurements, and a
resistor for calibration is not already
installed in the system, install a 100 ohm,
± 0.1%, 1/4 W resistor, in series, into the
output/power loop of the scale. Voltmeter
readings are shown in parentheses.
Step 3. If a voltmeter is used, attach the voltmeter
across the 100 ohm resistor.
Step 4. Adjust the transmitter Fine control for a 4
mA (0.4 V) reading on the meter. If neces-
sary, center the Fine control and adjust the
transmitter Coarse control first.
Step 5. Place a know weight on the scale. If possi-
ble, use a full scale weight for best results.