A Scale Technicians’ must have Tool!

The load cell simulator is a very important tool to have in your scale troubleshooting arsenal.  It is not a magic box to be afraid of.  A simulator is the best way to calibrate a load cell system when a live calibration is not practical.  It’s nothing different than hooking a scale to an indicator or load cell amplifier and putting test weights on and off the scale.  This is done much easier and quicker by just turning a knob.  Some transducer simulators have more bells and whistles, such as the ability to emulate more than 1 load cell, a vernier dial for fine adjustments, and more calibrated mV/V steps.

We’ll break down the three main uses for this tool which are Calibration, Scale System Setup, and Troubleshooting.

Weighing Indicator Calibration using a Load Cell Simulator

You can use the transducer simulator to calibrate the scale display by using some simple math.  First you’ll calculate the units/mv, below is an example.

A 10,000 lb capacity load cell with an output of 3.0020 mV/V (capacity/mV/V=pounds per mV) would be 3,331 pounds per mV.  After calculating this, you can then use this information to calibrate your load cell amplifier or indicator.  In this example you then take the nearest calibrated value of the load cells’ actual rated mV/V (3.0020) on the simulator, in this case 3mV/V.  Then multiply 3,331 by 3 (the calibrated rotary dial selection) this gives you the reading that the indicator should display at the 3mV/V calibrated step (9,993 lbs).  Calibrate the scale or amplifier accordingly.

For a multiple load cell application, take the sum of the capacity of the load cells and the average the mV/V output from all the load cells.  Apply the above formula.  It is important to use a simulator that has the feature to simulate multiple load cells like our SIM-4 load cell simulator.  We have found large difference between the results of simulating a single load cell and using the feature to select how many load cells are simulated.  This is caused by the simulator drawing more or less current from the indicator’s power supply.  In theory this should not happen, but more often than not it makes a substantial difference in the indicator’s readings.

Scale System Setup Using a Load Cell Simulator

A load cell simulator can be used to simulate different weights via the calibrated steps or the vernier adjustment if your simulator has this feature.  This is extremely useful when setting up a load cell system that uses setpoint controls such as a batching or check-weighing operation.  In the case when you have multiple setpoints that are close together in value, the vernier adjustment gives fine control of the mV/V output from the simulator.  Using a transducer simulator is much easier than having the scale hooked to the instrument and moving test weights on and off.

Troubleshooting Using a Load Cell Simulator

Scale technicians often use a simulator to test the analog to digital converter in a weight indicator.  The power supply can be tested as well by hooking up a simulator to put a load on the power supply.  If the scale system you are simulating has multiple load cells, it is important to use a simulator with the feature to simulate multiple load cells.  We have seen indicators from the field that have passed testing using a simulator set to simulate a single load cell and then have them fail once you change the unit to simulate multiple load cells.

Load Cell Simulator Conclusion

The uses we have listed explain how a simulator will save you time and money in the long run.  This is a must have tool for anyone who routinely works with load cell based electronics.
Load Cell Systems offers several different load cell simulators all made in the USA.