Signal conditioning

types, examples

1. SIGNAL CONDITIONING CIRCUITS By - Prof. Biswajit Karmakar Lecturer- Electrical Engg ( KPC )

2. Learning Objective At the end of this session you would be able to know :- 1. What is signal conditioning circuits. 2. What are the functions of a signal conditioning circuit 3. Examples of SCC 4. Real time usage

3. Introduction In electronics,  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 , signal conditioning includes voltage or current limiting and anti-aliasing filtering. In control engineering  it is common to have a sensing stage which consists of a  sensor , a signal conditioning stage where usually 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 stages.

4. Inputs Signal inputs accepted by signal conditioners include DC voltage and current, AC voltage and current, frequency and electric charge. Sensor inputs canbe  accelerometer, thermocouple,  thermistor ,  resistance ,thermometer , strain gauge or bridge, and LVDT or RVDT. Specialized inputs include encoder, counter or  tachometer, timer or clock, relay or switch, and other specialized inputs. Outputs Outputs for signal conditioning equipment can be voltage, current, frequency, timer or counter, relay, resistance or potentiometer, and other specialized outputs.

5. Processing Signal conditioning can include  amplification ,  filtering , converting, range matching, isolation and any other processes required to make sensor output suitable for processing after conditioning .   Filtering Filtering  is the most common signal conditioning function, as usually not all the signal frequency spectrum contains valid data. The common example is 50/60 Hz AC power lines, present in most environments, which cause noise if amplified.

6. Amplification Signal amplification performs two important functions : increases the resolution of the input signal, and increases its signal-to-noise ratio.   For example- the output of an electronic temperature sensor, which is probably in the milli -volts range is probably too low for an  analog-to-digital converter (ADC) to process directly.  In this case it is necessary to bring the voltage level up to that required by the 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

7. 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 External power is required for the operation of an active sensor. (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.

8. Some examples of signal conditioning circuits Vout Vin

9. Voltage devider circuit

10. summery We have seen that how a signal conditioning circuit   does the manipulation of an analog signal in such a way that it meets the requirements of the next stage for further processing.

11. Activity for you 1. List out five different types of signal conditioning units used in electronics circuits, Draw the ciruit diagrams and briefly define them. 2. What do you mean by OP-AMP ? Draw its basic circuit diagram and explain its operaion .

12. References https :// web.itu.edu.tr/yalcinme/files/courses/MMG/ch3_1%20SignalConditioning.pdf Sensors and Signal Conditioning, 2nd Edition by Ramón Pallás-Areny , John G. Webster : in this new edition https://www.analog.com/en/education/education-library/practical-design-techniques-sensor-signal-conditioning.html

13. Youtube & slideshare links