Hardy 1734-WS Installation & Operation Manual
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Electrical Check Procedures
Load Sensor/Point Input/Output
Measurements
The HI 1734-WS module is designed to
supply 5 VDC excitation to as many as
eight 350-Ohm load cells/points per
channel. The expected output from
each load cell/point will depend on the
mV/V rating of the load cell/point and
the weight.
For example, a 2mV/V load sensor will
respond with a maximum of 10 mVDC
at the load sensor’s full weight
capacity, which includes the weight of the vessel and the weight of the product as measured by the load
cell/point. Thus, if the load sensor’s weight capacity is rated at 1000 pounds, the load sensor will be 10
mVDC at 1000 pounds, 7.5 mVDC at 750 pounds, 5 mVDC at 500 pounds and so on.
A zero reference point will vary from system to system depending on the “Dead Load” of the vessel. “Dead
Load” is the weight of the vessel and appurtenances only, with no product loaded. In our example we will
assume the dead load to be 500 pounds.
NOTE:
The operating range for the scale in this example is 5-10 mVDC with a 500 pound weight range. After
zeroing the instrument, the 0 reading refers to the zero reference point and not absolute 0 mVDC or
absolute 0 weight.
NOTE:
Load sensor measurements are checked with a digital voltmeter at the load cell
connector on the front of the module or by using INTEGRATED TECHNICIAN with a
Hardy IT Junction Box. The scale calibration must be completed to enable IT to function
correctly.
Load Check
Place a load (weight) on the scale or vessel, and check to see if the weight reading on the input table changes in
the proper direction.
For example, if the display reads 100 pounds and a 20-pound weight is placed on the vessel or scale, the display
should read 120 or some value over 100. With the display reading 100 pounds, if a 20-pound load is placed on the
vessel or scale and the reading is 80 pounds, the reading is going in the wrong direction and indicates some
problem with the system.
If the display reads improperly or shows no change, something is wrong with the setup. If the display changes
weight in the proper direction, remove the weight and proceed to calibrate the instrument. Refer to Chapter 7 on
troubleshooting for additional help to determine the cause of the poor weight reading.
