How to connect the wires and wiring of the load cell to common problems? -Huaqiang Electronic Network

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The principle of the load cell: A load cell operates by using an elastic body, also known as a sensitive beam, which deforms elastically when subjected to external force. Attached to this elastic body is a strain gauge, which changes its resistance in response to the deformation. This change in resistance is then converted into an electrical signal—either voltage or current—by a measurement circuit, effectively transforming the applied force into an electronic output.

How to connect a load cell: First, identify the power supply (positive and negative), feedback (positive and negative), and signal (positive and negative) lines on the sensor interface of the display. If it's a 6-wire transmitter, the two wires with the lowest resistance are the excitation (power) lines. The other two are for the signal. For a 4-wire system, short the positive power supply with the positive feedback, and the negative power supply with the negative feedback. Then measure the remaining two wires for millivolt output and connect them to the signal input of the display.

Typically, red is used for power supply, black for ground, yellow for the positive signal, and white for the negative signal. Load cells can be connected using either a 4-wire or 6-wire configuration. A 4-wire system is more common and easier to use, but it may be affected by long cable runs and environmental temperature changes. In contrast, a 6-wire system requires a secondary instrument with a feedback interface, offering better accuracy and stability over long distances and in varying temperatures.

Load cell wiring diagrams:

In most weighing systems, 4-wire sensors are more commonly used. If you need to connect a 6-wire sensor to a 4-wire system, you can connect the feedback positive to the excitation positive, and the feedback negative to the excitation negative. However, it’s important to note that the signal lines (SIG+ and SIG-) differ between 4-wire and 6-wire sensors. Also, the SENSE+ and SENSE- lines are not the output signals—they are part of a feedback loop that helps the system compensate for voltage drops along the cable.

Common wiring issues with load cells: What is the difference between the power supply lines (EXC+, EXC-) and the sensor lines (SENSE+, SENSE+)? The number of wires varies depending on the sensor type (4 or 6 wires). Similarly, the module or transmitter may also support 4 or 6-wire connections. Whether to use 4 or 6 wires depends on your hardware setup. The general rule is: if you can use 4 wires, do so. Most load cells are 6-wire. When connecting to a 4-wire system, the excitation and feedback lines are typically shorted together.

It's crucial to understand that the SENSE+ and SENSE- lines are not the actual signal output. Instead, the signal output comes from the SIG+ and SIG- lines. The EXC+ and EXC- provide power to the load cell, but due to voltage drop along the cable, the actual voltage received by the sensor may be less than the supply voltage. For example, if the supply is 10V and there's a 0.5V drop, the sensor will receive only 9.5V. If the sensor has a 2mV/V rating, the maximum output would be 19mV instead of 20mV. To ensure accurate readings, the feedback loop must send the actual voltage back to the system. Shorting EXC+ to SENSE+ and EXC- to SENSE- is only recommended for short-distance setups, otherwise, measurement errors may occur.