Electrical components, connectors and wiring standards for load cells
In precision force measurement, the electrical signal path between the transducer and the measuring electronics is just as crucial for data integrity as the sensor itself. If cables, connectors, or terminal connections introduce electrical noise or resistance, the accuracy of the entire measurement chain will be compromised during operation.
Understanding electrical components, connector specifications and Wiring standards for load cellsThe integration of load cells into systems is essential for maintaining system accuracy and preventing equipment damage, particularly with torque transducers and multi-axis sensors. Detailed documentation, including the... Cable wiring diagram for load cells, connector wiring diagram for load cells and Wiring diagrams of sensors – on the individual product pages as well as bundled in the support resource Interface Electrical Wiring and Diagrams are available to support you.
Electrical components of the sensor and signal behavior
Interface load cells utilize a Wheatstone bridge circuit, which consists of Strain gauges Strain gauges consist of variable resistance and are bonded to a mechanical element. When a force is applied, the electrical resistance of the strain gauges changes. This change provides the data that is recorded when measuring force, torque, or weight.
Since strain gauge bridges are passive networks, they require an external input voltage, typically between 5 V and 10 V. The output signal of the bridge is a differential analog voltage, measured in millivolts per volt (mV/VAt full capacity, a sensor with a sensitivity of 2 mV/V and a supply voltage of 10 V will deliver a maximum output of only 20 millivolts. Because this signal voltage is extremely low, it is highly susceptible to electromagnetic interference and attenuation. Therefore, using sensors designed to handle this type of noise is crucial in your selection process.
Cable configurations and connector definitions
The transition from the internal bridge circuit to the external one Data acquisition system requires specific cable designs and connection hardware.
cable types
- 4-core cables: This configuration includes positive and negative power supply lines as well as positive and negative signal lines.
- 6-core cables: In addition to the power and signal lines, 6-core cables contain two sense lines. These lines monitor the exact voltage at the strain gauge bridge and enable the measuring electronics to automatically compensate for voltage drops over long cable runs.
- Integrated and extension cables: Integrated cables are permanently bonded to the sensor housing during manufacturing, thus minimizing contact resistance. Extension cables are connected to the sensor via a plug interface and increase the distance to the measuring electronics.
Connectors and plug-in interfaces
- Connector socket: The physical plug or socket that is mounted directly on the sensor housing. Standard designs often use multi-pin bayonet connections to ensure a mechanically secure connection.
- mating connector: The corresponding connector is attached to the cable assembly, which snaps into the sensor socket. These assemblies often feature environmental seals to insulate the electrical contacts from moisture and contaminants.
RESOURCES: Our complete Guide to sensor connection cable assemblies helps you set the correct connection. Also, download our Brochure on cables and connectors to download them so they are readily available for future reference.
Cable length and wiring modes
Cables possess an inherent electrical resistance that affects signal transmission depending on distance and configuration.
Resistance and distance
In a 4-wire configuration, long cable lengths result in an uncalibrated voltage drop across the feed lines, reducing the voltage arriving at the bridge and thus lowering the sensor output signal. Using standard 28 AWG copper wire, this translates to a sensitivity loss of approximately 0,37% per 3 meters (10 feet). Because copper resistance is temperature-dependent, long 4-wire runs can exhibit thermal range drift with changing ambient temperatures. Implementing a 6-wire configuration or calibrating the system with the exact cable length eliminates this issue.
Wiring standards and modes
Sensors are manufactured and wired for specific operating modes, such as tension or compression. These standards define how the bridge outputs data in relation to the direction of the applied load. Adhering to the correct wiring standard for the upscale mode ensures that the measuring electronics register a positive value when the primary design force is applied—this prevents calculation errors in multi-cell configurations such as weighing platforms or structural test rigs.
TIPP: Read Interface cable assemblies 101 for further information as well Understanding cable length and temperature effects.
Color coding matrices for wiring and system protection
Adherence to a standardized wire color matrix is crucial when terminating sensor connections on the measuring electronics or in the junction box.
A common industrial wiring standard uses the following pinout:
- Red: Positive feed. This is the positive voltage input to the bridge.
- Black: Negative feed. This is the negative voltage input, or ground.
- Green: Positive signal. This is the positive millivolt output.
- White: Negative signal. This is the negative millivolt output.
- Blank or yellow: Shield. This is the ground wire for electromagnetic shielding.
Due to the wide range of sensors and measurement electronics, Interface offers cable and connector wiring/pin colors in many additional colors (up to 24 or more). All color guides for Interface wiring can be found online in the references. Color coding of electrical wiring diagrams for load cells, torque transducers, 3-axis sensors and 6-axis sensors.
Electrical pitfalls of faulty wiring
Errors during connection completion lead to predictable system failures. Here are three common errors.
#1 – Signal Inversion
Swapping the positive and negative signal wires will not damage the hardware, but it will invert the data output signal. Compressive forces will be registered as tensile forces, which will distort automated control loops.
#2 – Component damage
An accidental cross-connection between a power supply line and a signal line can conduct voltage directly into the low-voltage measurement channels of the data acquisition system or across the sensitive strain gauges, often causing permanent electrical failure. If you have damaged your device, contact us immediately for assistance with repairs. Repair support.
#3 – Complexity in multi-axis sensors
Multi-axis sensors comprise up to 24 separate pins and color codes across multiple channels. Verifying the exact connector pinout is mandatory before applying power to ensure proper channel alignment. Crosstalk or to prevent components from burning out. Detailed diagrams – including the 3-axis wire color coding, 3-axis circular connector wire color coding and 6-axis wire color coding – are useful resources for verifying these complex multi-channel configurations.
Technical resources on electrical wiring and cables
Achieving highly accurate measurement data depends entirely on the integrity of the electrical connections between the sensor and the measurement electronics. Simple wiring errors or incorrect pin assignments can lead to inverted data, thermal drift, or irreversible damage to components of the data acquisition system.
Technical specifications, pinouts, and wiring documentation are included on the individual product pages throughout the website. For comprehensive reference materials, users can access the Interface support on our dedicated resource Interface Electrical Wiring and Diagrams Access. This central library provides immediate access to specific reference matrices and schemes, including:
- Cable wiring diagram for load cells
- Connector wiring diagram for load cells
- Wire color code for load cells
- Wire color coding for torque transducers
- 3-axis wire color coding
- 3-axis circular connector wire color coding
- 6-axis wire color coding
For laboratory use, as a field reference, or for integration into system design, you can use the complete Interface document with electrical wiring diagrams Download to ensure exact adherence to factory wiring standards.
If you cannot find the information you need to make the correct connections between your sensor, cable and your measurement electronics, contact Interface's product experts for technical support.