Multi-axis Load Cell FAQ

Multi-axis Load Cell FAQ

Note that for version 4.5.0.1 of Mach-1 Motion or later with an ESP302 controller + interconnection board + load cell smart connectors, the load cell calibration matrix is hardcoded and must be modified by a Biomomentum technician.

How are multi-axis load cells installed on the Mach-1?

Multi-axis load cells have a 3 step process to be installed:
  1. Ensure the amplification box is plugged into the controller:
     or 
  2. Ensure the load cell is plugged into the amplification box (barrel connector with thread):

  3. Use the 3x M2 bolt included with the load cell to attach it to the Mach-1's load cell mount:

What orientation should be used when installing multi-axis load cells?

If looking from above directly towards the front of the system, the wire of the multi-axis load cell should go towards the user's left should (between 6-and-9-o'clock). This will ensure that the X & Y axes of the system are aligned with the Fx and Fy axes of the load cell. If the load cell is installed one of the 2 other possible ways during testing. The Fx and Fy axes could be rotated up to 60 degrees.

How can you identify a damaged multi-axis load cell?

There are many ways to identify a damaged load cell. The most obvious would be a permanent "overload" message in the Mach-1 Motion software when this load cell is active. Here are some other troubleshooting steps:
  1. The first step would be to lightly touch the load cell with a finger while Mach-1 Motion is open and active. This will ensure the software is monitoring the correct load cell (6 different coloured lines should be visible in the load output graph).

  2. Performing a calibration of the load cell should give a calibration factor of between 0.950 and 1.050. If using a t-shaped calibration weight holder, the calibration verification test can be performed at multiple different positions by rotating the holder to reach every cardinal direction.

    Older models of the Mach-1 can have two different positions where the weight can be installed:

    Newer versions of the Mach-1 simply have a hook and weight:

  3. If a calibration verification test is giving an "invalid calibration" error, the load output graph can be monitored during application of the weight to ensure the values make sense. For example, if a ~100gf weight is applied, the Fz axis should read approximately 1N.
  4. Biomomentum can be contacted at info@biomomentum.com to help install a custom calibration matrix named FTGages. This calibration matrix will simply output the voltage at each strain gauge instead of the converted Fz, Fx, Fy, etc. values. This can be used to identify strain gauges which are saturated (only read a constant, maximum voltage).

Can I limit the force on certain axes of my load cell?

The load cell's calibration matrix can be found in the following folder on the Mach-1 PC: C:\Users\Public\Documents\Biomomentum\Mach1Motion.
The Mach-1 Motion software uses the FTXXXXX.cal calibration files to convert voltages to load readings. These calibration files should not be moved, renamed, nor modified without the help of a Biomomentum technician as they are critical to the functioning of the load cell.
If necessary, a Biomomentum technician can limit the load cell in a certain axis (e.g. Fz could be limited to 5N) for the purpose of a test. Once the force reaches 5N, the Mach-1 Motion software will immediately stop all motors and display a "overload" error instead of continuing the test.

What is the process of repairing a damaged multi-axis load cell?

Although the load cell internal structure is not usually repairable, the amplifier box(es) can be reused with a replacement load cell and will reduce the cost:
  1. First, communicate with Biomomentum (info@biomomentum.com) to confirm that the load cell is damaged and it is not a wiring issue.
  2. Once confirmed, Biomomentum will supply both a quotation for repair and a return merchandise authorization (RMA) form.
  3. Once the form is filled, instructions to ship the damaged load cell and amplifier box(es) to Biomomentum will be sent by email.
  4. A first inspection will be performed, followed by a recalibration of the amplifier box(es) with a new load cell.
  5. A second quality control inspection will be perform on the load cell and amplifier box(es).
  6. Finally, the new load cell and recalibrated amplifier box(es) will be returned by shipment.

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