Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 18)

14 Load Cell and Weigh Module Handbook
9.0 Calibration Using a Load Cell Simulator
This is perhaps the simplest and fastest method of scale calibration, particularly on large-capacity scales. It is less accurate than
the other methods described. A major disadvantage is that it doesn’t test the scale mechanically or take into account the
influence of friction, piping, support deflection, etc. However, the method is sometimes sufficient for process weighing
applications that need not meet legal-for-trade requirements.
The following example is based on the premise that a power supply of exactly 10V DC is used. Measure your power
supply for the exact excitation voltage to obtain your results.
To calibrate with a simulator:
1. Disconnect the cable from the junction box at the indicator.
2. Connect a load cell simulator to the indicator. The simulator should have a vernier for fine adjustments.
3. Set the simulator to 0.0 mV/V and zero the indicator.
4. Set the simulator’s output (in mV/V) to simulate the output of the load cells at full scale capacity (ignoring dead load for
now). To find the simulated full scale output, use the following formula:
Total Load Cell mV/V Output = Simulator mV/V Setting
Total Load Cell Capacity Displayed Weight
For example:
If four 5,000lb 3 mV/V load cells are used for a 10,000lb capacity scale, the simulator setting expected when 10,000lb
is placed on the scale can be determined by the following:
3.0 mV/V = Simulator mV/V Setting
------------ --------------------------
20,000lb 10,000lb
Therefore, the simulator should be set to 1.5 mV/V.
5. Adjust the indicator to display the capacity of the scale (10,000lb in our example) and set the indicator’s span.
6. Adjust the simulator’s output in steps (1.0mV/V, 0.5mV/V,
0.0mV/V) and verify the indicator’s linearity and return to zero.
7. Remove the simulator and reconnect the load cells. Recalibrate the indicator’s zero point to take account of the actual
dead weight of the vessel.
8. The accuracy of this method can be greatly increased by using a high-resolution 5½ digit volt meter to measure the
indicator’s actual excitation voltage and to verify the actual mV output from the simulator. Those more accurate figures
can then be used in the above procedure.