Load Cell Wiring Basics
Load cells can have four or six wires. Both versions have positive and negative signal and excitation lines. The six-wire load cell also has positive and negative sense lines. Sense lines are linked to the sense connections of the system’s indicator, sometimes through a junction box, allowing the indicator to know a load cell’s actual voltage.
The sense lines continuously send information to the indicators, so if there is a voltage drop between the indicator and load cell, the indicator automatically adjusts the voltage. This compensates for the loss of voltage or amplifies the return signal to compensate for reduced power to the load cell.
Load cell wires are color-coded to ensure proper connections. Each brand uses its own color codes, so technicians need manufacturer-provided wiring color guides. Some manufacturers, including Rice Lake Weighing Systems, offer online wiring guides to assist technicians.
What Is Load Cell Trimming
Load cell trimming, or load cell summing, involves tying load cell output signals together. This happens in a junction box, which sends the summed signal to the indicator. It’s necessary to trim load cells when the weight distribution to each load cell isn’t equal. Trimming ensures the scale weighs correctly regardless of where the load is applied to the scale.
For example, in vessel loading processes, the presence of agitators or materials such as powder can affect how material and weight are distributed to each load cell.
Load cell manufacturing processes also permit some variation between load cells, which can cause load cell outputs to vary and result in inaccurate measurements. If trimming isn’t done, accuracy may be off due to the slight variations from manufacturing.
