View source for Signal conditioning

{{short description|Manipulation of an analog signal into a form suitable for further processing}}
{{Refimprove|date=November 2007}}

In [[electronics]] and [[signal processing]], '''signal conditioning''' is the manipulation of an [[analog signal]] in such a way that it meets the requirements of the next stage for further processing. 

In an [[analog-to-digital converter]] (ADC) application, signal conditioning includes voltage or [[current limiting]] and [[anti-aliasing filter]]ing.

In [[control engineering]] applications, it is common to have a sensing stage (which consists of a [[sensor]]), a signal conditioning stage (where usually [[Amplifier|amplification]] of the signal is done) and a processing stage (often carried out by an ADC and a [[micro-controller]]). [[Operational amplifiers]] (op-amps) are commonly employed to carry out the amplification of the signal in the signal conditioning stage. In some [[transducer]]s, signal conditioning is integrated with the sensor, for example in [[Hall effect sensor]]s.

In [[power electronics]], before processing the input sensed signals by sensors like voltage sensor and current sensor, signal conditioning scales signals to level acceptable to the microprocessor.
{{Further|Digital signal conditioning|Digital electronics}}

==Inputs==
Signal inputs accepted by signal conditioners include [[direct current|DC voltage]] and current, [[alternating current|AC voltage]] and current, [[frequency]] and [[electric charge]].  Sensor inputs can be [[accelerometer]], [[thermocouple]], [[thermistor]], [[resistance thermometer]], [[strain gauge]] or bridge, and [[Linear variable differential transformer|LVDT]] or [[Rotary variable differential transformer|RVDT]].  Specialized inputs include encoder, counter or [[tachometer]], timer or clock, relay or switch, and other specialized inputs.  Outputs for signal conditioning equipment can be voltage, current, frequency, timer or counter, relay, resistance or potentiometer, and other specialized outputs.

==Processes==
Signal conditioning can include [[Amplifier|amplification]], [[filter (signal processing)|filtering]], converting, range matching, isolation and any other processes required to make sensor output suitable for processing after conditioning.

===Input Coupling===
Use [[AC coupling]] when the signal contains a large DC component. If you enable AC coupling, you remove the large [[DC offset]] for the input amplifier and amplify only the AC component. This configuration makes effective use of the ADC dynamic range

=== Filtering ===
[[Electronic filter|Filtering]] is the most common signal conditioning function, as usually not all the signal frequency spectrum contains valid data. For example, the 50 or 60&nbsp;Hz AC power lines, present in most environments induce noise on signals that can cause interference if amplified.

=== Amplification ===
Signal [[Amplifier|amplification]] performs two important functions: increases the resolution of the input signal, and increases its signal-to-noise ratio. {{citation needed|date=March 2014}}  For example, the output of an electronic [[temperature sensor]], which is probably in the millivolts range is probably too low for an [[analog-to-digital converter]] (ADC) to process directly.{{citation needed|date=June 2012}} In this case it is necessary to bring the voltage level up to that required by the [[Analog-to-digital converter|ADC]].

Commonly used amplifiers used for signal conditioning include [[sample and hold]] amplifiers, peak detectors, log amplifiers, antilog amplifiers, instrumentation amplifiers and programmable gain amplifiers.<ref>"Data acquisition techniques using PCs." Academic-Press - Pages 44-47</ref>

===Attenuation===
Attenuation, the opposite of amplification, is necessary when voltages to be digitized are beyond the ADC range. This form of signal conditioning decreases the input signal amplitude so that the conditioned signal is within ADC range. Attenuation is typically necessary when measuring voltages that are more than 10 V.

===Excitation===
Some sensors require external voltage or current source of excitation, These sensors are called active sensors. (E.g. a temperature sensor like a thermistor & RTD, a pressure sensor (piezo-resistive and capacitive), etc.). The stability and precision  of the excitation signal directly relates to the sensor accuracy and stability.

===Linearization===
Linearization is necessary when sensors produce voltage signals that are not linearly related to the physical measurement. Linearization is the process of interpreting the signal from the sensor and can be done either with signal conditioning or through software.

===Electrical isolation===
Signal isolation may be used to pass the signal from the source to the measuring device without a physical connection. It is often used to isolate possible sources of signal perturbations that could otherwise follow the electrical path from the sensor to the processing circuitry. In some situations, it may be important to isolate the potentially expensive equipment used to process the signal after conditioning from the sensor.

Magnetic or optical isolation can be used. Magnetic isolation transforms the signal from a voltage to a magnetic field so the signal can be transmitted without physical connection (for example, using a transformer). Optical isolation works by using an electronic signal to modulate a signal encoded by light transmission (optical encoding). The decoded light transmission is then used for input for the next stage of processing.

===Surge protection===
A [[surge protector]] absorbs voltage spikes to protect the next stage from damage.

==References==
{{reflist}}

[[Category:Electrical engineering]]