MBI block diagram and basic features

A microprocessor based instrumentation (MBI) system uses a microprocessor to collect data from transducers, process it and display, store or use it for control.

Block diagram

Sensor -> Signal conditioner -> S/H -> ADC --+
  ^                                          v
  |                                +------------------+
PLANT                              | Microprocessor   |<-> ROM/RAM
  |                                | (CPU, I/O ports) |<-> Keypad,
  v                                +------------------+    Display,
Actuator <- Driver <- DAC <----------------+  |           Printer,
                                              +-> Serial link

Blocks

• Sensor/transducer: converts the physical quantity (temperature, pressure, flow) into an electrical signal.
• Signal conditioner: amplifies, filters and linearises the signal to the ADC input range.
• Sample and hold and ADC: converts the analog signal to digital words.
• Microprocessor with ROM and RAM: executes the program, processes data, takes decisions.
• I/O ports (8255, UART): connect keypad, display, printer and other devices.
• DAC, driver and actuator: convert the control word back to an analog or power signal for the final control element.

Basic features

1. Programmable operation, easily changed by software.
2. Intelligence: decision making, alarms, linearisation, calibration.
3. High accuracy and repeatability due to digital processing.
4. Data storage, display, printing and communication with computers.
5. Flexible and expandable, with low size, power and cost.