What is the wiring color code on my load cells? How can I verify it is correct?

Attached you will find a color code chart covering the standard load cells and load sensors offered by Hardy Instruments, and another chart that covers most other load cell manufacturers. There are many color code combinations across the industry and Hardy Instruments has adopted the "West Coast" version for our Advantage and legacy load sensors, there are load sensors (single point models) in the Hardy product line that are standard east coast color codes.  Hardy duplicated that standard to reduce confusion if replacing load cells in an existing system.   We add a color code flag to all load cell cables before shipping to our customers.

The West Coast color code is:  (Advantage, Advantage Lite and Legacy series)

Red     = + excitation
Black   = - excitation
Green  = + signal
White  = - signal
Gray   = + C2
Violet  = - C2

The East Coast color code is: (HILPH, OEM SPA and SP series)

Green     = + excitation
Black   = - excitation
White  = + signal
Red  = - signal
Gray   = + C2
Violet  = - C2


In instances where there are violet and gray wires, these are C2® plus (gray) and C2® minus (violet) connections. C2® second generation calibration is a process by which a scale system is electronically calibrated without the use of test weights, material substitution, hydraulic force or external electronic simulators. This feature is only offered by Hardy Instruments.

The above color code represents 80 percent of the load cells and load sensors offered by Hardy Instruments, but we use multiple vendors and not all are the same.  To determine your load cell wiring color codes consult the load cell installation manual, look on the load cell cable for a color code marker, look at the load cell certificates, and diagrams for the color code listing, or see the attached Tech Note for additional information.

There are many different color combinations in the industry and no standard. If you cannot find supporting documentation you can use a multi-meter using the ohms scale. You may need to use a little guesswork too. Here are some hints on how to determine your load cell wiring color code:

1. The shield wire is usually thicker, clear, or yellow and an open ohm reading as measured across any other load cell wire.

2. The black wire is normally the negative excitation or negative signal input wire. You can use this as a reference to attempt to determine the remaining wire combinations. The ohm readings for the excitation vary from 350 to 1100 ohms. The excitation ohm readings are normally higher than the signal or output reading.

3. When there are more than 4 wires (not counting C2® wires), the additional wires are probably sense lines and are the same as the excitation connection. The ohm reading will be the same as the excitation wires, but will read a short when you read the plus excitation to the plus sense leads. The sense plus to the excitation plus wires are terminated in the same terminal of the summing junction box. The excitation minus to the sense minus will read as a short. Minus excitation and minus sense wires are terminated in the same terminals of the summing junction box. Typically green and blue are paired as plus excitation/sense and Brown and black are minus excitation/sense.

4. Chart the ohm reading combinations for each wire in combination with a second wire until all combinations are read. (Black to red, black to green, black to white, red to green, etc.) Now is when the guesswork comes into play. If you find ohm readings like 1000 and 1100, the 1100 ohms wires are the excitation. Combinations of 350 and 350-