Load Cell Wiring: Excitation, Signal & Sense Wires Explained
When it comes to installing or troubleshooting a load cell, wiring is one area that often creates confusion. Terms like Excitation+, Excitation-, Signal+, Signal-, Sense+ and Sense- may look technical, but understanding their role is actually quite simple.
Whether you are working with a 4-wire or 6-wire load cell, knowing what each wire does is important for accurate and stable weight measurement. A wrong connection can lead to incorrect readings, unstable weight values, or even communication issues between the load cell and the weight indicator.
In this article, let's understand load cell wiring, including excitation, signal and sense wires, in simple terms.
What Is Load Cell Wiring?
A load cell converts mechanical force or weight into an electrical signal. Inside the load cell, strain gauges are arranged in a Wheatstone bridge configuration. When weight is applied, the resistance of these strain gauges changes slightly, producing a small electrical output.
For the load cell to work properly, it needs:
A power supply to energize the Wheatstone bridge
A signal path to send the weight measurement to the indicator
In some cases, sense wires to compensate for voltage loss
This is where excitation, signal and sense wires come into the picture.
What Are Excitation Wires?
Excitation wires provide the electrical supply required to power the load cell.
They are generally marked as:
Excitation+ (E+ or EX+)
Excitation- (E- or EX-)
You can think of excitation as the input power for the load cell. The weight indicator or transmitter supplies a stable voltage through these wires, which energizes the Wheatstone bridge inside the load cell.
Without excitation voltage, the load cell cannot generate an output signal.
Simple example
Think of a load cell like a bulb. The excitation wires are similar to the power supply that allows the bulb to function. Once the load cell receives excitation voltage, it becomes ready to detect changes caused by applied weight.
What Are Signal Wires?
Signal wires carry the actual weight measurement from the load cell to the weight indicator.
They are usually marked as:
Signal+ (S+ or SIG+)
Signal- (S- or SIG-)
When weight is applied to the load cell, the strain gauges experience deformation. This causes a very small change in electrical voltage across the Wheatstone bridge.
The signal wires carry this small output voltage to the indicator, where it is amplified, processed and converted into a weight reading.
The important thing to remember is that the load cell signal is very small, usually measured in millivolts. This is why proper wiring, shielding and connections are important. Even small electrical interference or poor connections can affect the final weight reading.
What Are Sense Wires?
Sense wires are found in a 6-wire load cell.
They are generally marked as:
Sense+
Sense-
At first glance, sense wires may seem unnecessary because they are connected alongside the excitation circuit. However, they perform an important role, especially when long cables are involved.
When electricity travels through a long cable, a small amount of voltage can be lost due to cable resistance. This is known as voltage drop.
If the actual excitation voltage reaching the load cell changes, the output signal can also be affected.
Sense wires monitor the actual voltage present at the load cell. The weight indicator can then compensate for any voltage drop occurring in the cable.
In simple words, sense wires help the system know what voltage is actually reaching the load cell.
4-Wire vs 6-Wire Load Cell Wiring
The main difference between a 4-wire and 6-wire load cell is the presence of sense wires.
A 4-wire load cell has:
Excitation+
Excitation-
Signal+
Signal-
This type of wiring is commonly used when cable lengths are relatively short and voltage drop is not a major concern.
A 6-wire load cell has:
Excitation+
Excitation-
Signal+
Signal-
Sense+
Sense-
The additional sense wires help compensate for voltage variations caused by long cable runs or changes in cable resistance.
This is particularly useful in applications where accuracy is critical, such as industrial weighing systems and large weighbridges.
A Simple Way to Understand All Six Wires
Here is an easy way to remember the function of each wire:
Wire | Function |
Excitation+ | Supplies positive power to the load cell |
Excitation- | Supplies negative power or return path |
Signal+ | Carries the positive measurement signal |
Signal- | Carries the negative measurement signal |
Sense+ | Monitors actual positive excitation voltage |
Sense- | Monitors actual negative excitation voltage |
Important: Wire Colours Are Not Always the Same
One common mistake during load cell installation is assuming that every manufacturer follows the same wire colour code.
For example, one load cell manufacturer may use red for Excitation+, while another may use a completely different colour.
Therefore, never rely only on wire colours. Always check the load cell's datasheet, wiring diagram or manufacturer's documentation before making any connection.
Final Thoughts
Understanding excitation, signal and sense wires makes load cell wiring much easier to troubleshoot and install correctly.
Excitation wires power the load cell. Signal wires carry the weight measurement. Sense wires help maintain accuracy by compensating for voltage drop, especially in long cable installations.
A properly connected load cell is essential for accurate and reliable weighing. So, whether you are working with a 4-wire or 6-wire load cell, always verify the wiring configuration before connecting it to the junction box, weight indicator or transmitter.
Because in precision weighing, even a small wiring mistake can lead to a big difference in the final reading.
KANTA KING
Website: https://www.kantaking.com/
Contact Us: +91.9560915555
Email: info@kantaking.com
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