MBI definition and importance of microcomputer

An MBI system is an instrumentation system in which a microprocessor or microcontroller is the central unit that acquires data from sensors through signal conditioning and ADC, processes it by program, and gives the result to displays, storage or actuators for monitoring and control.

Why a microcomputer is important in instrumentation design

• It replaces a large amount of hard-wired logic with a program, which reduces cost and size.
• It performs calculations (linearisation, averaging, scaling, PID control) that analog circuits do poorly.
• It gives intelligence: decisions, limit checking, alarms, auto ranging.
• Calibration, offset and drift errors are corrected in software.
• Modifications are made by changing the program, not the hardware.
• It handles many channels by multiplexing and communicates with other computers.

Example: A furnace temperature meter. A thermocouple signal is amplified, digitised, linearised in software (thermocouple non-linearity), compensated for cold junction, compared with the set temperature, displayed on an LCD and used to switch the heater. A hardware-only instrument would need separate analog circuits for each of these.

Basic features

1. Programmability and flexibility.
2. Accuracy, repeatability and stability.
3. Decision making and automatic control.
4. Data logging, display and communication.
5. Self-test, low cost, compact and low power.

Block structure: sensor -> conditioner -> ADC -> microprocessor (ROM, RAM, I/O) -> DAC/actuator, display and communication.