--- title: "MBI block diagram and basic features" subject: "Instrumentation II" chapter: 1 key: "semester_5/instrumentation_ii:mbi-block-features" source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/mbi-block-features site: BCT Engineering --- # MBI block diagram and basic features Instrumentation II · Chapter 1: Microprocessor Based Instrumentation System - Asked in: 2071 Chaitra, 5 marks; 2076 Asoj, 5 marks (asked 2 times) - Answer checked by Claude Sonnet 5.5 on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/mbi-block-features - Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-1 ## Question Explain the block diagram of a microprocessor based instrumentation system. What are the basic features of a microprocessor based instrumentation system? ## Short answer An MBI system comprises sensor, signal conditioner, S/H, ADC, microprocessor with ROM/RAM, I/O ports for display, keypad, and DAC/driver/actuator for control. It offers programmability, intelligent decisions, high accuracy, data storage/display, communication, and low cost/size. ## Answer 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 ```text 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the signal conditioner do in an MBI system? A. Amplifies, filters and linearises the signal to the ADC input range B. Converts digital words to analog C. Stores the program D. Drives the actuator Answer: A. It prepares the sensor signal for the ADC. (Key point: Role of signal conditioner) 2. What is the role of the S/H and ADC? A. Convert the control word into power signal B. Convert the analog signal into digital words for the microprocessor C. Display data on LCD D. Store data in ROM Answer: B. They digitise the conditioned signal. (Key point: Role of ADC and S/H) 3. Which blocks apply the control action to the plant? A. ADC and sensor B. ROM and RAM C. DAC, driver and actuator D. Keypad and display Answer: C. The control word is converted by the DAC, amplified by the driver and applied by the actuator. (Key point: Output path) 4. What are ROM and RAM used for in the block diagram? A. ROM holds data, RAM holds program permanently B. Both only drive the display C. They convert signals to digital D. ROM holds the program and RAM holds data Answer: D. Program is kept in ROM and data in RAM. (Key point: ROM and RAM roles) ## Close variants set in other exams - [Features of microprocessor based instrumentation](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-features) — Instrumentation II, chapter 1, asked 4× ## Related in Instrumentation II - [MBI block diagram, advantages and DMA](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-block-advantages-dma) — Instrumentation II, chapter 1 - [MBI block diagram and advantages in industry](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-block-advantages) — Instrumentation II, chapter 1 - [Types of microprocessor based instrumentation systems](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-types) — Instrumentation II, chapter 1 - [MBI features; open vs closed loop compared](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-features-open-closed) — Instrumentation II, chapter 1 - [Rationale for microprocessor; open-loop MBI; DMA](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Arationale-open-loop-dma) — Instrumentation II, chapter 1 - [Case study: revamping MBI system for CEO](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-ceo-revamp) — Instrumentation II, chapter 10 ## Related in other subjects - [Instrumentation system with block diagram](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Ainstrumentation-system) — Basic Electronics Engineering, chapter 7, asked 3× - [Microprocessor based system and bus organization](https://www.bctengineer.com/question.md?key=semester_4%2Fmicroprocessor%3Amp-based-system-bus-organization) — Microprocessor, chapter 1, asked 5× - [Microprocessor-based transmission line protection](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Amicroprocessor-line-protection) — Switchgear and Protection, chapter 8, asked 2× - [Communication system and block diagram](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Acomm-system-block-diagram) — Basic Electronics Engineering, chapter 5, asked 7×