ISO threads on tension load cells

The load cell’s effort axis is generally materialised by the axes of the two threads or female threads at either end. These must be co-linear, allow for an easy connection, and be of good mechanical quality, with both the structure applying the load to the load cell and the structure holding it.

The best solution is to use threads compliant with ISO standards, preferably within the first series of thin ones, such as M110x4 / M64x4 / M52x3 / M30x2 / M20x1.5 / M12x1.75, and with tight geometric adjustment tolerances, of a 4h or 4H type, in order to keep any float with the fixation pieces to the minimum.

Eliminating the influence of interfering forces and torques

The second requirement involves eliminating the influence of interfering forces and torques on the measurement performed on the axis of the load cell. As long as the transducer is fitted with two threads at either end, this is an easy procedure, performed by using two rod ends fixed mounted on either side of the transducer. These fittings define two rotation centres which will only allow the transfer of forces exerted on the axis connecting these two centres.

Providing that these fittings are in good condition and mounted on the load cell with a reduced level of mechanical float, they guarantee decoupling by eliminating any action operating beyond the rod end fitting and enabling the measurement to be improved by a factor of 10. For very large loads, it is impossible to use rod end fittings. In this case, it is necessary to take specific precautions to ensure that the force to be measured is strictly uniaxial and goes through the load cell effort axis. Nevertheless, the accuracy of the measurement is not as high.

NOTE : Spanish version /en/tecnologia/sensores-de-fuerza/sensor-de-fuerza-en-traccion