Architecture of Smart Sensors, Essential parts, Signal Conditioners, Filtering, Converters

1. Dr.T.Mrunalini
AP (SrG), EIE, KEC
Architecture of Smart Sensors

2. Block Diagram of Smart Sensor

3. Features of Smart Sensors
 Automatic Ranging and calibration of data through build-in
system
 Data Acquisition system (DAS) and storage
 Automatic linearization of non linear transfer functions
 Auto correction of offsets, temperature compensation
 Self tuning control algorithms
 Communicates through serial bus
 Remote monitoring, multi sensing and remote
configuration of devices

4. Architecture of Smart sensor

5. Important Components
 Sensing element and Transduction element
 Interfacing Hardware/ Data Acquisition System
(DAS)
 Signal Conditioning Devices
 Conversion Devices
 Filters
 Programming Devices (Processors)
 Communication Interfaces

6. Signal Conditioning
 Analog signals need to be correctly prepared before
they can be converted into digital form for further
processing.
 Signal conditioning is an electronic circuit that
manipulates a signal for the next stage of processing.
 Many data acquisition applications involve
environmental or mechanical measurement from
sensors, Examples : temperature and vibration.
 Sensors require signal conditioning before a data
acquisition device can effectively and accurately
measure the signal.

7. Signal Conditioner Types
 Voltage and high-voltage signal conditioners
 Current signal conditioners
 IEPE signal conditioners (or ICP/piezoelectric signal
conditioners)
 Charge signal conditioners
 Strain gauge signal conditioners
 Load cell signal conditioners
 Thermocouple signal conditioners
 RTD signal conditioners
 Thermistor signal conditioners
 LVDT signal conditioners
 AC signal conditioning
 DC signal conditioning
 Digital signal conditioners

8. Requirements of Signal Conditioner
The required elements of signal conditioners are
 Electrical isolation
 The right connectors for sensor connections
 Measurement range selection
 Signal filtering (e.g. anti-aliasing filtering)
 Conformance with sensor requirements.

9. Signal Filtering
 Aside from setting the input gain, the most important
function of a signal conditioner is to provide filtering.
 At the very least, a two or four-pole low-pass filter is often
needed to suppress or reduce electrical noise, which can
get into the signal from the testing environment.
 Anti-aliasing filters (AAF) prevent wrong readings by
automatically adjusting the front-end filter according to
the selected sample rate

13. Converters
 Converters and Expanders allows to connect other types
of buses or interfaces to standard monitoring HW group
devices.
 The output can be a continuous value, an extension of the
number of DI inputs or DO outputs.
 Signal Converter : Converts signals from sensors to
industrial current signals, converts analog input signals to
analog output signals, normalizes signals, or isolates
signals.

14. A/D Converters
 An A/D converter is a device that converts analog
signals (usually voltage) obtained from environmental
(physical) phenomena into digital format
 Conversion involves a series of steps, including
sampling, quantization, and coding.
 Electrically sophisticated and high-speed processing
are performed digitally in CPUs and DSPs.

15. Operation of A/D Converters

16.  The A/D converter breaks up (samples) the amplitude of
the analog signal at discrete intervals, which are then
converted into digital values.
 The resolution of an analog to digital converter is
typically expressed by the number of bits.
 In the above case of a 3bit A/D converter, the upper value
(b2) is referred to as the Most Significant Bit (MSB) and
the lowest value (b0) the Least Significant Bit (LSB).

17. The graph below shows the relationship
between the analog input and digital output

18. Analog Signal to Digital Signal Conversion
Methods
 Sampling: The process of taking amplitude values of the
continuous analog signal at discrete time intervals
(Sampling Period Ts).
Sampling Period Ts = 1/Fs (Sampling Frequency)
 Sampling is performed using a Sample and Hold (S&H)
circuit.
 Quantization: involves assigning a numerical value to
each sampled amplitude value from a range of possible
values covering the entire amplitude range (based on the
number of bits).
 Coding: Once the amplitude values have been quantized
they are encoded into binary using an Encoder.

20. THANK YOU