Rockwell Automation 937CU-AISTR-DC1 Strain Gauge Converter Installation Instructions - Manual (Page 46)

However, because the total mass to be measured is greater, the range must also be entered|.
Under Input > Calibration > Range > Set the weight to be measured must be entered, in the example
35 t. With this setting the value 100 % will be displayed at 35 t if the unit is changed to %.
The
Strain Gauge Converter has now been calibrated including the whole measuring chain.
Outputs
Current output
The current output must only represent the net value (the weight of the load). In the menu Output >
I
out
> Gross/Net the option Net must therefore be selected.
The adjustable range relates to the maximum cell load. Because the maximum cell load is not
reached with a full tank (full
truck = 20 t, maximum cell load = 60 t) the value 20 t must be
entered here.
Relay outputs
To prevent overloading a relay must be triggered as a limit value relay if 20.5 t is exceeded. This
means that the relay must be parameteri
zed as a limit value switch with the switching direction "Max";
as a switching point the 20.5 t must be entered. As hysteresis a value of approx. 1 % of the range is
recommended, i.
e. 250 kg (0.25 t). The relay must energise once the switching point has been
exceeded, the direction of action must therefore be entered as "active".
To prevent the relay from switching during the
truck entering the scales a time of 60 s can be
entered under the menu item Relay > Trip alarm > Delay. Limit overruns of less than 60 s duration
will then be ignored.
Operation
An empty
truck enters the scales. After short-circuiting the inputs of the trigger input previously
parameterized as "Tare" a zero point calibration is carried out. The truck is then loaded and the Strain
Gauge Converter displays only the weight of the load.
At the current output the weight of the load is represented by 4
mA for the empty truck and 20 mA
for the fully loaded truck.
Via the RS 485 interface the weight of the load (net weight) can be queried by a PLS via the
command Get_value_ch_1 and be processed numerically.
Bul. 937
C Strain Gauge Converter Installation Instructions
44