Hardy HI 2204LT Weight Transmitter - Manual (Page 12)

HI 2201LT/HI 2204LT
8
brations instructions before attempting to calibrate the
instrument.
Calibration
Controls
Coarse (Zero) The Coarse Control is used to remove large deadloads
or offsets such as the weight of the scale’s platform,
container or any other constant weight on the load
cells which is part of the weighing equipment itself.
This control can subtract as much as 65% of full scale
from the transmitter’s output.
Fine (Zero) This control is a fine offset adjustment. Its range is
sufficient to fine tune the COARSE adjustment.
Span The Span Control adjust the gain of the transmitter. It
determines how many millivolts (of transducer signal)
per volt (of transducer excitation) will be represented
by the 4 ma to 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
deadload compensation is subtracted by the COARSE
Zero adjustment.
Calibration
Procedures The measuring instruments used in the following pro-
cedure must be designed so that test leads are isolated
from ground. These are either “floating” and/or “iso-
lated” and/or “differential” types.
Insertion of any measuring device, or voltage drop-
ping resistor for a measuring device in the output/
powers loop requires that the power supply voltage be
high enough to supply the extra voltage (See Input-
Strain Gage Transducer). The following is an example
using load cells in a weighing application.
Step 1. Remove any weight from the scale. Allow
deadload to remain. If deadload is counter-
balanced, also allow counterbalancing to
remain.