Multi-Axis Force Sensor Selection: Three Force Channels or Six Components?

Multi-axis force sensor selection begins with a list of the quantities the test must report. Three force components describe Fx, Fy and Fz. They do not independently resolve the three moments Mx, My and Mz. Before comparing capacity or outside diameter, decide whether the task needs directional force only or a full force-and-moment measurement.

Multi-axis force sensor selection: count measured components first

The three-axis ratings above retain the catalogue's kg and t notation. Record the agreed engineering units in the calibration and acquisition configuration. A label describing a sensor as miniature or multi-dimensional is not enough to establish which components are available; use the actual channel and axis documentation.

A single force reading and a known lever arm can support a moment calculation only under the assumed loading geometry. It does not turn a three-channel device into an independent six-component measurement system. If additional forces or couples can act on the fixture, use a measurement arrangement that can distinguish them.

Select from simultaneous loads, not the largest number in a table

List the maximum expected component on each axis for each operating case, including fixture weight and off-centre force application. The moment produced by an offset load still acts mechanically on a three-axis sensor even when the instrument does not report it.

Do not assume every axis can be loaded to its individual maximum at the same time. Obtain the combined-load limits and the permitted moments for the exact sensor. Where those limits are not published, they remain an open selection requirement, not permission to use all catalogue ratings simultaneously.

Choose capacity with the smallest useful signal in mind as well. A large axial preload and a small lateral force may require different channel gains. Specify the required increment and useful range for each component rather than copying one accuracy or resolution target across all axes.

Channel sensitivity is part of the configuration

The MV-LC0242 reference gives nominal sensitivity of 2.0 mV/V for Fx and Fy, but 1.2 mV/V for Fz. At an illustrative 5 V excitation, those correspond to 10 mV and 6 mV nominal full-scale signal changes. One common scale factor would therefore be wrong even before accounting for the different axis capacities.

The MV-LC0240 reference lists nominal 1 mV/V on its three force channels. Its published cross-talk reference is 2% F.S.; that is not evidence that cross-axis effects can be ignored in every fixture. Confirm the applicable calibration data and how the selected readout handles channel interaction.

Obtain the channel identification, excitation requirements, calibration coefficients and any supplied compensation matrix. Establish whether compensation is already applied by the conditioner or must be applied in software. Applying it twice, omitting it or using coefficients from another serial number can make plausible-looking data incorrect.

Check coordinates with physical loads

Define the sensor axes on the fixture drawing and record how they relate to the machine or test coordinates. Connector orientation alone is not a sufficient axis convention. Apply a known force in an identified direction and check the sign and component distribution before running the normal test.

For six-component measurement, both coordinate orientation and the point about which moments are reported matter. Moving the reporting point changes moment values even when the physical load is unchanged. Keep the sensor-origin loads available for checking mechanical limits; a software change of origin does not remove the load on the sensor.

Validate individual channels and representative combined-load cases using an agreed reference method. Record unwanted responses on the other channels rather than checking only the intended axis. A one-axis calibration check cannot demonstrate that the complete multidirectional measurement is correct.

Questions when specifying a directional test

Q1. Are separate amplifiers acceptable for the different axes?

They may be, if their excitation, gain and timing suit the sensor and test. For changing loads, verify that the values combined into one vector refer to the same time interval. Independently filtered or delayed channels can distort the apparent direction during a transient.

Q2. What should be sent with the model enquiry?

Provide the required components, per-axis loads, simultaneous load cases, fixture drawing, load application point, required increments and recording rate. Include the proposed acquisition equipment through METRAVON enquiries. For a robot wrist, also use the robot integration guide to assess tool offsets and controller requirements.

Summary

Choose the measured components before choosing capacity. Keep each axis's range, sensitivity and calibration associated with the correct channel, and verify combined loads and coordinates in the assembled fixture. These checks distinguish useful directional data from several numbers that merely change when a load is applied.