Signal conditioning delivers improved application results

New and simplified features and increased capabilities are offered in signal conditioners, helping improve accuracy and performance by optimizing transmitted signals from mission-critical devices.

By Jeff Thornton, Red Lion Controls February 1, 2009

Signal conditioning is used to convert, amplify or isolate a signal from one device to another. The most common application is converting a sensor signal such as a thermocouple, RTD or process signal and preparing it for use in the next stage of the process.

The basic function of a signal conditioner is to accept an input signal such as a current, voltage or frequency, then to provide a proportional signal in the desired analog output format. This process may include simply converting the signal to an analog current in proportion to the input frequency, amplifying a low-level signal for transmission over a long cable run or isolating it from all the other devices in the system, for example.

In some applications, a signal conditioner may also be used in conjunction with auxiliary devices such as an amplifier. Since many small devices may produce a weak analog signal, amplifiers may be used to magnify the signal and re-transmit it to the next stage of the process. While less common, a device’s signal may at times be too large, in which case attenuation is needed as part of the conditioning process to lower the signal level for the next stage of the process.

Keep it simple

Traditionally, signal conditioners have been very application-specific, accepting an input signal in only one format and outputting the specific signal that is required. As the variety of processing
applications grew and device technology advanced, the number of dedicated signal conditioners required to accommodate all of the varying inputs and required outputs also increased.

To reduce module inventories and simplify conditioning for a broad range of disparate devices, universal signal conditioners have now become well established as a multi-faceted solution. A single universal module can accept potentiometer, resistance, dc current and voltage input, then provide a suitable analog output signal. Some signal conditioners are also available with setpoint control, which allows them to also provide machine or process loop control if desired.

In addition to accepting numerous inputs, some signal conditioners can be custom-calibrated to suit unusual input and output scaling. For example, with the correct programming, a signal conditioner can produce an output that is the reverse of the received input. These calibration advancements, along with universal signal acceptance, have resulted in some signal conditioners now being capable of more than 100 input-to-output configurations.

Increased programmability

As technology has grown in sophistication and many electronic components have decreased in size, these conditioners have had to follow suit — often creating challenges for users. Smaller signal conditioners are well suited for optimizing DIN-rail real estate, allowing many more conditioners to fit within a defined space. However, with this smaller size, the dual inline programmable (DIP) switches used for setup have also become smaller and more difficult to manipulate, making signal conditioner programming more challenging and time-consuming. In fact, many of these DIP switches are becoming virtually too small to see — much less switched into the proper position.

To combat this problem, some signal conditioners are now available with separate programming modules. While they consume a bit more DIN-rail space, these modules provide the benefit of easily accomplished push-button configuration. Using a separate programming module also allows users to establish a program and quickly transfer all parameters to each duplicated signal conditioning module in a system. Simply snap on the programming module, and the conditioner can be configured with the push of a button. Once the programming is complete, the programming module is removed, and the unit becomes a dedicated signal conditioner. Security is increased because no one has access to the signal conditioner settings except through the programming module.

Along with expediting configuration, these detachable programming modules may also offer an LCD display that can indicate process variables — much like a panel meter — to facilitate system monitoring. This simplifies troubleshooting by allowing operators to view process values and status updates in real time, as well as access advanced equipment functions and collected data.

Proper signal conditioning can improve accuracy and performance by optimizing transmitted signals from mission-critical devices such as sensors and transducers, and by allowing the data to be simply converted and used. The combination of a smaller size, universal design and simplified programming has now made signal conditioners more efficient and effective to use in a wider variety of applications.

Author Information
Jeff Thornton has extensive industry experience, working at Red Lion Controls for 32 years. Thornton began in production and is now product manager for several Red Lion product divisions.