The primary use of signal conditioners is to convert one kind of electrical signal into another. Generally, this process is necessary when the original signal cannot easily be processed by conventional instruments and needs to be converted into a format that is easily interpreted. The conditioner accepts signals such as frequency, electric charge, AC voltage and current, and DC voltage and current. In addition, conditioners may process and interpret inputs from sensors that measure strain, resistance, temperature or acceleration. Relays, switches, clocks and encoders can also provide input. In turn, signal conditioners output a variety of signal types.
1. Signal Conditioner Functions
The three main steps in signal conditioning include filtering, amplification and isolation. Inefficiencies can result in loss of data, inaccurate output and other problems. In order to determine what type of signal conditioner is best for you, it is important to know the type of input you will be processing, the desired type of output, the quality criteria for the signal, available power and isolation needs.
Signal conditioners come in a broad range of accuracy. One of the factors that will affect the degree of accuracy you will need in your conditioner is the accuracy of your other equipment, especially the sensor providing the input. If your sensor is not highly precise, an extremely accurate signal conditioner will not lead to more accurate output. For maximum efficiency and cost-effectiveness, every part of your signal processing system should possess approximately the same degree of accuracy. Otherwise, the device with the higher precision is just being wasted.
Flexibility, on the other hand, is generally an important feature which allows your signal conditioner to process a wider range of signal types. Typically, many manufacturers offer hardware or software flexibility as an additional option. In many cases, the ability to deal with a larger range of signals can also increase precision and calibrate for sensor or system errors due to factors such as voltage drops. Flexibility also increases your ability to maintain and replace components and change signal conditions without affecting other parts of the system.
Many signal conditioners use isolation at one or more points throughout the processing. In this context, isolation means that there is no direct electrical connection between two circuits or points. Signal conditioners with isolation use optical couplers or transformers to send signals from one point to another. Using magnetic or optical energy for transmission, as opposed to electrical current, has the purpose of protecting the device from voltage spikes and of getting rid of possible ground loops.
Signal conditioners typically employ isolation in one or more of the following four areas. Power isolation is when both input and output signals are isolated from the power common. It protects the signal transmission from variations in power source grounding. Three-way isolation exists when power, input and output each are completely isolated. This allows the signal conditioner to interface with three different systems that are grounded separately. Another option is to have the output isolated, and the input and power connected. This is preferable when signals transmit to the field from a grounded system. Isolating only the input is common when the signals are coming into a grounded system.
Depending on your intended types of input and output, as well as the configuration of your system, you can determine which signal conditioner components you want to be isolated. Generally, at least some degree of isolation is important to the quality of your signal output. Look for isolation ratings that exceed your needs, as wear and tear over time tends to degrade isolation, leading to decreased performance.
In an industrial setting, there are several factors that can interfere with your signal conditioner. Notably, radio frequency interference and electromagnetic interference can present serious problems. Today’s signal conditioners may come with built-in protection. One common method of radio frequency interference protection is placing the circuit inside a Faraday shield. The other is to reconfigure component combinations in a way that will decrease the effects of the interference. While the results are comparable, the latter approach is more flexible and cost-effective, since it allows you to calibrate equipment even when interference is present. Many manufacturers likewise provide built-in protection from electromagnetic interference.
6. Amplification and Attenuation
Depending on the type of input your signal conditioner is to receive, you may want one with signal amplification capabilities. The desirable amplification range, again, will depend on your input. For example, equipment with very low voltage, such as an electronic temperature sensor, may need amplification for the signal conditioner to process and output its signal. On the other hand, you may need to reduce high-voltage signals by using attenuation to bring it within input range.
7. Built-In Versus Front-End
Signal conditioners can come as built-in, providing everything you need to process a specific type of signal. The advantage is that you have everything you need in one piece of equipment. However, built-in conditioning is virtually single-purpose. If your needs ever change or expand, your conditioner will quickly become obsolete. The other option is front-end conditioning, where multiple devices can be connected and interchanges depending on the specific application. This modular arrangement offers far greater flexibility, but can be time-consuming to set up. However, it has been simplified through improved wireless technology.
Another important consideration when selecting a signal conditioner is the quality and durability of its hardware. Many conditioners are used in harsh industrial environments and may be exposed to extreme temperatures and other hazards. If this is the case, the optimal solution is highly durable housing that can still be opened for calibration.
The first step towards purchasing the optimal signal conditioner for you is to understand your requirements. Keep in mind that the most expensive system is not necessarily the one you need, and may even be counterproductive if your other devices are not compatible or you cannot allot sufficient space, power or bandwidth to operate it effectively. Many manufacturers can provide consultation to help you obtain the signal conditioner that will work best for your current needs and is adaptable enough to survive potential future changes.