Standard load cell cable typically has a foil tape shielding, a braided tinned copper shield, and an outer PVC jacket to insulate and protect the wires. Of course, there are other things to keep in mind besides when choosing a load cell cable. The summing box adds the signals from each load cell together which is then sent to the indicator to determine the weight based on the indicators calibration.Ħ-wire cable is used in these types of applications because of the ability to repair sections without re-calibrating the system, to run long lengths of wire, and to adjust to temperature changes in uncontrolled environments. These four load cells are then connected to a junction or summing box before the indicator. A hopper or tank system may use four load cells with one under each foot to measure weight. Rice Lake 6-Wire Standard Load Cell CableĦ-wire cable is most commonly used in commercial applications where multiple load cells are employed. This is important as 6-wire cables have no temperature compensating system which means that technicians have the ability to cut or extend a length of 6-wire cable without compromising the cable or re-calibrating the entire system. Unlike the 4-wire cable, the sense wires in a 6-wire cable allow the indicator to adjust the output voltage with an amplifier to compensate for voltage drops over long distances or varying temperatures. These sense wires are used to factor in the resistance changes and subsequent voltage drops over the length of the cable. They have all the same wires as the 4-wire cable but also have two additional sense wires, both positive and negative.
Just as with the naming convention of 4-wire cable, 6-wire cable has 6 wires (again, duh). Over long distances, 6-wire is the cheaper option and provides more accuracy in the system. So what does one do if you have to run the cable over a long distance or in unpredictable environments? You either increase the size of the cable or switch to a 6-wire load cell cable. Keep in mind, if a 4-wire cable has to be replaced, the system generally needs to be calibrated again. This generally voids warranties as well on standalone scales. Additionally, because 4-wire load cell cable is calibrated to its length and thermally compensated, it should not be shortened. The table below shows the recommended wire gauge over various lengths.Īlmost all commercial scales that have an indicator attached use 4-wire cable because it's cheaper and the length required is minimal. 4-wire cables are typically used in shorter lengths as a thicker cable is needed to contain the voltage drop over longer spans of wire. As the cable's length and temperature increase, so does its resistance. The resistance of a load cell cable varies with length and ambient temperature. To understand why we have to look at a little physics. Rice Lake 4-Wire Standard Load Cell CableĤ-wire cable is typically used in short lengths from the scale base or junction box to the indicator. This signal is then converted inside the indicator to display a numerical weight. The output to the indicator is typically between 0 and 30 millivolts and is sent back through the signal wires. As the strain gauge deforms from a mass placed on the load cell, the resistance changes. The excitation wires deliver an electrical current to the strain gauge (a type of resistor) in the load cell, typically between 5 and 10 volts. Why is it called 4-wire? It has 4 wires (duh) including power + (sometimes referred to as excitation), power -, signal +, and signal. The most common type of load cell cable is the 4-wire type. So what types of load cell cables are there? 4-Wire Load Cell Cable This proportional electrical signal is then relayed back to the indicator which displays the numerical weight based on the signal strength. The load cell acts as a transducer that then creates an electrical signal proportional to the force applied to it. Power originates from the indicator through the excitation wires in a load cell cable.
Simply put, load cell cables act as both a power and communication channel, bridging the indicator and load cells together. What type of load cell cable are you going to need to get the job done right? You’ll have to consider a number of things, including length, temperature, and other environmental factors. There are many things to consider when building custom weighing applications but today we are only going to focus on the load cell cables. You know what load cells you need for your next project (or maybe you don't, we can help with that) and now you need to integrate them into the rest of your system.