INDUSTRIAL AUTOMATION AND CONTROL CHAPTER 3

1. Chapter-3
Signal Conditioning
Suvendu Mondal
AP,EED,SurTech
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2. Filtering:
• Filtering is an important technique in signal conditioning, which is the
process of modifying a signal to improve its quality, to make it
suitable for further processing, or to meet certain specifications.
Filtering involves removing or attenuating unwanted frequencies or
noise from a signal while retaining the desired signal components
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3. Filtering
• There are different types of filters that can be used for signal conditioning, depending on the application and
the characteristics of the signal. Some common types of filters include:
• Low-pass filter: This filter allows low-frequency components of a signal to pass through while attenuating
the high-frequency components. It is useful for removing high-frequency noise from a signal.
• High-pass filter: This filter allows high-frequency components of a signal to pass through while attenuating
the low-frequency components. It is useful for removing low-frequency noise from a signal.
• Band-pass filter: This filter allows a specific range of frequencies to pass through while attenuating all other
frequencies. It is useful for isolating a specific frequency band of interest in a signal.
• Band-stop filter: This filter attenuates a specific range of frequencies while allowing all other frequencies to
pass through. It is useful for removing a specific frequency band from a signal.
• Notch filter: This filter attenuates a narrow range of frequencies around a specific frequency while allowing
all other frequencies to pass through. It is useful for removing a specific frequency component from a signal.
• These filters can be implemented using various electronic components such as resistors, capacitors, and
inductors, or using digital signal processing techniques. The choice of filter type and implementation
depends on the specific application requirements and constraints.
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4. Amplifying
• In signal conditioning, "amplifying" refers to the process of increasing the
amplitude, or strength, of an electrical signal while preserving its
waveform. Amplification is an essential step in signal processing because it
helps to improve the signal-to-noise ratio and make the signal more robust
for further processing or transmission.
• Amplification can be achieved using various types of electronic devices,
such as operational amplifiers (op-amps), transistors, or vacuum tubes. Op-
amps are commonly used in signal conditioning circuits because they are
highly versatile, have high gain and bandwidth, and are easy to use.
• In signal conditioning, amplification is usually followed by other processing
steps, such as filtering, level shifting, or digitization, depending on the
specific application requirements. The overall goal of signal conditioning is
to transform the raw signal into a format that is suitable for the next stage
of processing or transmission.
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5. Isolation
• In signal conditioning, "isolation" refers to the process of breaking the electrical connection
between two or more parts of a system to prevent unwanted electrical interactions between
them. Isolation is essential in many applications, especially those involving high voltages, high
currents, or different ground potentials.
• Isolation can be achieved using various techniques, such as opt couplers, transformers, or
capacitive coupling. Opt couplers use light to transmit signals across an isolation barrier, while
transformers use magnetic fields. Capacitive coupling involves placing a capacitor between the
input and output of a circuit to block DC and low-frequency signals, while allowing high-frequency
signals to pass.
• Isolation is often used in signal conditioning circuits to protect sensitive equipment or signal
sources from damage caused by high voltages or ground loops. Ground loops occur when two or
more parts of a system are connected to different ground potentials, creating a loop that can
cause noise and interference in the signal. Isolation can help break the ground loop and reduce or
eliminate the interference.
• Isolation can also be used to protect users or operators from electrical hazards, such as electric
shock. Isolated power supplies are often used to provide power to equipment in medical or
industrial applications where safety is a critical concern.
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6. ADC
• ADC stands for Analog-to-Digital Converter, which is an electronic device used in signal conditioning to
convert analog signals into digital signals. In signal processing, analog signals are continuous signals that vary
over time, while digital signals are discrete signals that are represented by a sequence of binary digits or bits.
• ADCs are used in many applications, including data acquisition, control systems, instrumentation, and
communication systems, to convert analog signals into a digital format that can be processed by digital
circuits such as microprocessors, digital signal processors (DSPs), or FPGAs. The process of converting analog
signals into digital signals involves two steps: sampling and quantization.
• Sampling is the process of measuring the amplitude of the analog signal at regular intervals, or "samples,"
over time. The interval between samples is called the sampling rate, which is usually expressed in samples
per second (SPS) or Hertz (Hz). The higher the sampling rate, the more accurately the analog signal can be
represented in the digital domain.
• Quantization is the process of assigning a discrete numerical value to each sample, which represents the
amplitude of the analog signal at that point in time. The number of bits used to represent each sample
determines the resolution of the ADC, which is the smallest change in the analog signal that can be
accurately represented in the digital domain. The resolution is usually expressed in bits, and the number of
possible values that can be represented by an ADC is 2^n, where n is the number of bits.
• ADCs come in many different types and configurations, including successive approximation ADCs, delta-
sigma ADCs, flash ADCs, and pipeline ADCs, each with its own advantages and disadvantages depending on
the specific application requirements.
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7. DAC
• DAC stands for Digital-to-Analog Converter, which is a type of electronic device used in signal
conditioning to convert a digital signal into an analog signal. Signal conditioning refers to the
process of modifying or manipulating an input signal to achieve a desired output signal.
• In many electronic systems, digital signals are used for processing and control purposes, but the
output of the system may need to be in analog form to interface with other components or
systems. A DAC is used to convert the digital signal into an analog signal that can be used to drive
an output device such as a motor, speaker, or display.
• The process of converting a digital signal into an analog signal involves several steps. First, the
digital signal is processed by a digital signal processing circuit to generate a stream of binary data
that represents the original signal. This binary data is then fed into the DAC, which converts it into
an analog signal by assigning a voltage or current level to each binary value.
• DACs are available in various types and configurations, depending on the application
requirements. Some common types of DACs include binary-weighted DACs, R-2R ladder DACs,
sigma-delta DACs, and current-output DACs. Each type of DAC has its own strengths and
weaknesses, and the choice of DAC depends on the specific requirements of the application.
• Overall, DACs are an essential component in signal conditioning and are used in a wide range of
electronic systems, including audio and video equipment, instrumentation, and control systems.
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8. Sensor protection circuits
• Sensor protection circuits are electronic circuits designed to protect
sensors from damage due to overvoltage, overcurrent, and other
electrical disturbances. These circuits are commonly used in
applications where sensors are exposed to harsh environments or
where they may be subjected to extreme electrical conditions.
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9. Sensor protection circuits
• There are various types of sensor protection circuits, each with its specific function and design. Some common
types include:
1. Overvoltage protection circuits: These circuits protect sensors from high voltage spikes or surges that can
damage or destroy the sensor. They typically use a combination of clamping diodes and transient voltage
suppressors to limit the voltage and prevent damage.
2. Overcurrent protection circuits: These circuits protect sensors from excessive current flow that can cause
overheating or burnout. They often incorporate current-limiting resistors, fuses, or circuit breakers to prevent
damage to the sensor.
3. EMI/RFI protection circuits: These circuits protect sensors from electromagnetic interference (EMI) and radio
frequency interference (RFI) that can cause signal distortion or data loss. They may use shielding, filtering, or
decoupling techniques to minimize the effects of EMI/RFI on the sensor.
4. Reverse polarity protection circuits: These circuits protect sensors from damage due to incorrect polarity
connections. They typically use diodes or MOSFETs to block current flow in the wrong direction.
5. Short-circuit protection circuits: These circuits protect sensors from damage due to short-circuits in the wiring
or circuitry. They may use current-limiting resistors or fuses to prevent excessive current flow.
• Overall, sensor protection circuits are essential components in many electronic systems that rely on sensors.
They help to ensure the accuracy and reliability of sensor measurements and prevent costly damage or
downtime due to sensor failure.
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10. Signal transmission and noise suppression
• Signal transmission and noise suppression are critical aspects of
electronic systems design. Signals can be affected by noise, which can
cause errors or distortions in the signal. Therefore, it's important to
have techniques to minimize or eliminate noise in signal transmission.
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11. Signal transmission and noise suppression
• Here are some methods for signal transmission and noise suppression:
1. Shielding: Shielding is a technique used to protect the signal from electromagnetic interference (EMI) and radio
frequency interference (RFI). Shielding is often done by surrounding the signal conductor or cable with a
conductive material like copper or aluminum foil. This shield helps to block any external EMI or RFI from
entering the signal path.
2. Twisted pair cables: Twisted pair cables are another method for reducing noise in signal transmission. In a
twisted pair cable, two conductors are twisted together. The twisting helps to cancel out any external
electromagnetic fields that may be present, reducing noise in the signal.
3. Grounding: Proper grounding is essential for reducing noise in signal transmission. By grounding the signal and
the equipment, any unwanted electrical signals can be diverted to ground instead of interfering with the signal.
4. Filtering: Filters are used to suppress unwanted frequencies in the signal. There are several types of filters,
including low-pass, high-pass, band-pass, and band-stop filters. Filters can be designed to attenuate or eliminate
noise in the signal path.
5. Amplification: In some cases, amplification can be used to improve the signal-to-noise ratio. Amplifiers can
boost the signal, making it easier to detect and reducing the impact of noise.
6. Signal processing: Signal processing techniques can be used to remove noise from the signal. These techniques
include signal averaging, digital filtering, and spectral analysis.
Overall, signal transmission and noise suppression are essential aspects of electronic system design. By employing
these techniques, engineers can improve the accuracy and reliability of the signals used in their systems.
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12. Estimation of errors and calibration
• Signal conditioning is the process of amplifying, filtering, and
manipulating an analog signal to improve its quality and make it
suitable for further processing. In this process, it is essential to
estimate and minimize errors, and calibrate the system to ensure
accurate and reliable measurements.
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13. Estimation of errors and calibration
• Estimation of errors: One of the most important aspects of signal
conditioning is the estimation of errors. There are various sources of
errors in signal conditioning, such as noise, offset, gain, linearity, and
temperature drift. To estimate these errors, one can use techniques
such as signal-to-noise ratio (SNR) measurement, offset and gain
calibration, linearity measurement, and temperature drift analysis.
These techniques can help to identify and quantify the sources of
errors and provide a basis for error correction.
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14. Estimation of errors and calibration
• Calibration: Calibration is the process of adjusting a system to ensure
that it performs accurately and reliably. In signal conditioning,
calibration involves adjusting the gain, offset, and other parameters
to eliminate errors and ensure that the output signal matches the
input signal. Calibration can be done using various techniques such as
self-calibration, external calibration, and automated calibration.
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15. Estimation of errors and calibration
• In summary, estimation of errors and calibration are crucial steps in
signal conditioning. By estimating errors and calibrating the system,
one can ensure accurate and reliable measurements, which is
essential in many applications such as instrumentation, control
systems, and data acquisition systems.
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