How Signal Conditioners Work
Signal conditioning refers to the process of turning the raw output from a load cell into a usable signal. Load cells themselves do not measure or read the electrical signal that is passed through them. The wires carrying the signal are soldered to strain gauges which are in turn adhered to the body of the cell. Change in the shape of the load cell changes the shape and thereby the resistance of the strain gauges through which the current passes. The result is a change in the output signal from the load cell. Without additional components of the weighing system to receive and interpret this signal, the load cell itself would not be very useful.
The data contained in the load cell’s output signal is typically picked up and used by a digital display, PC, PLC, or data logger. This equipment is usually unable to read and interpret the signal its raw form. This is where signal conditioners come in.
Signal conditioners clean up and modify the output signal from the load cell and send it on to the next component of the system.
Signal conditioning refers to a series of processes used to complete this task. The type of signal modification required for a system depends upon the qualities of the signal itself and the equipment to which its being transmitted. Signal conditioning functions fall into three general categories 1) noise reduction 2) adjusting the size of the signal 3) conversion to the desired format. The most common functions of a signal conditioner are explained as follows:
Analog to Digital Conversion:
By nature of its design, the signal produced by a load cell is analog. Even digital load cells initially produce an analog signal, but include an internal signal conditioner that converts it to digital. When a digital signal is required by other components of a weighing system, ADC’s are a necessary component of that system. While analog signals are faster and easier to process and take up less bandwidth, digital signals are less affected by noise and distortion. Digital signal processing is also easily stored, more flexible, has higher accuracy, and can be transmitted over longer distances.
Amplification:
The output signal from a load cell is often not strong enough to be interpreted by the next component of the system. Amplification is the process of strengthening the signal without corrupting the data.
Filtering:
The signal from a load cell may have noise intermingled with the data. The process of filtering separates and filters out the noise and enables the requisite information to move through the system.
Linearization:
Linearization is required when the signal data (mV) does not have a linear relationship to the force applied (lbf, kgf, gf, etc). Most load cell systems require only two points of reference during calibration, 0%, and 100%. With linearization, points are added in between where necessary to achieve more suitable linearity.
Excitation:
Strain gauge load cells require an electrical current from an external power supply in order to function. Most signal conditioners have the ability to supply the necessary excitation to the load cell.
Isolation:
The purpose of signal isolation is to break ground loops, which are a very common source of inaccuracies. When DC signal wires have paths to ground at both ends, a ground loop is created. A ground loop introduces an additional and incalculable amount of current into the loop, distorting the true measurement.
Load Cell Central supplies a wide range of signal conditioners able to perform all functions listed in this blog and more. Our signal conditioners are ideal for any load cell system, including batch weighing, process control, and factory automation systems. To view our line of signal conditioners, please visit our website at 800loadcel.com. For questions or more information, please email us at sales@800loadcel.com or call 800-LOADCEL.
