Depending on the model, the load cells may have a cable with 4 or 6 wires plus the screen. The 6-wire models, in addition to having the terminals of power supply + and power supply – and signal + and signal -, have 2 additional wires called Sense + and Sense – which may also be denominated reference.
The resistance of an electrical cable varies depending on temperature and length, given that we can say that as the temperature and the distance changes there is a voltage drop that the 6-wire system allows to be compensated without affecting the measurement.
The 4-wire load cells are thermally compensated and calibrated in relation to the length of the cable which is supplied as standard; to not compromise the calibration and compensation it is not recommended to shorten the cable of a 4-wire load cell; in the case of the weighing plant there is a weighing indicator or transmitter with a 6-wire input and a junction box-parallel, we recommend using a 6-wire cable to connect to the weighing indicator – transmitter to compensate the voltage drop on the stretch of cable between the junction box and the indicator itself.
If the indicator has a 4-wire input, it is recommended to use a shielded cable with a significant cross-section (minimum 1 sq.mm) in order to contain the voltage drop between the junction box and the weight indicator.
All these measures do not have to be considered with the 6-wire load cells.
The Sense (reference) wires are connected to the sense terminals of the weight indicator, so that this can measure and adjust the amplifier on the actual voltage that arrives to the load cells. The 6-wire load cells are therefore preferred over those with 4 wires, also on these load cells there are no limitations in the event the installer wants to shorten the cables.