Acquiring a Force Offset

he values displayed by the “Force Data Text” display have been offset and scaled by the values stored in the Force-plate calibration file. Thus they should read close to zero when no force is applied to the Force plate.

In the case the force values displayed by ODIN are not above or under few newtons (>5N or <-5N) then the plate needs to be reset. There are two types of offset: hardware and software. The hardware offset will re-initializes the core hardware components of the force plate system in order to minimize any offset in the analogue forceplate signals. It is necessary to do an hardware offset first. AMTI plate amplifiers have an reset button. Press on it to hardware rest the plate. Other types of plate may accept a reset signal which is generated by the “acquire force offset” command.

Having done that, the raw force values need to be check. If the force values are still above the threshold (>5N or <-5N) even after having performed a hardware offset, then it is necessary to perform a software offset. The software consists in acquiring analogue data for a short period of time. The average of each individual channel will be calculated and set as a software offset. The offset will then be subtracted at each frame in order to have a null value when no force is apply to the force plate(s). The software offset is acquired when clicking on: Hardware > Acquire Force Offset. The following message will be displayed:

Display of the analogue offset on the analogue text display

The user may want to remove the force offset. To remove the acquired force offset, simply click on Hardware > Clear Force Offset.