Instrumentation system with block diagram

An instrumentation system is a system used to measure, display, record and control a physical quantity (temperature, pressure, flow, strain, etc.) by converting it into an electrical signal and processing it.

Block diagram

 Physical    +-----------+  +-------------+  +-----------+
 quantity -->| Transducer|->| Signal      |->| Signal    |
 (input)     |  (sensor) |  | conditioning|  | processing|
             +-----------+  +-------------+  +-----+-----+
                                                   |
                    +-----------+   +-----------+  |
                    | Recorder/ |<--| Display / |<-+
                    | controller|   | indicator |
                    +-----------+   +-----------+

Function of each block

1. Transducer / sensor: converts the physical quantity into a proportional electrical signal (e.g. a thermocouple converts temperature to voltage).
2. Signal conditioning: amplifies, filters and linearises the weak signal, and removes noise. Bridge circuits and instrumentation amplifiers are used here.
3. Signal processing / conversion: converts the analog signal to digital (ADC) and processes it with a microcontroller or computer.
4. Display / indicator: shows the result on a meter, LCD or LED.
5. Recording / control: stores the data (data logger) or uses it to control the process (feedback to an actuator).

Example: a digital thermometer, made of a thermistor, amplifier, ADC, microcontroller and LCD.