Digital Multimeter: Handheld Solution

A Handheld Digital Multimeter (DMM) is a low-cost instrument used to measure AC and DC voltage, AC and DC current, and resistance. Five system level blocks are common to handheld DMM designs: Signal Conditioning and A/D conversion of the input signal, LCD/LED/Keypad, Control and Data Processing, Memory/Peripheral devices, and Power Management. Implementation specifics will obviously vary depending on the feature set of the meter.

The common core subsystems are:

• Analog Front-End – Signals are initially passed through a signal conditioning subsystem which amplifies or attenuates the analog signal in preparation for further conditioning, depending on whether the measurement is AC volts, DC volts, current, or resistance. Precision amplifiers and analog to digital converters are used to facilitate resolutions up to 4 1/2 digits on modern handheld DMMs.

• LCD/LED/Keypad – Entry level handheld DMMs offer basic monochrome 7 segment displays while higher end models offer 1/4 VGA OLED displays to accommodate the data logging features that have been recently added to the traditional DMM.

• Control and Data Processing – Executes measuring processes and controls interface with memory and peripheral devices. It also performs real-time analysis of acquired signals such as min/max, averaging, and conversion to engineering units.

• Memory/Peripheral Devices – Measurements results are stored in EEPROM or FLASH memory as a data log that can be uploaded to a PC via USB interface.

• Power Management and Conversion – converts the input battery power to run various functional blocks.

 TI has a wide range of products like amplifiers, ADCs, Power, Interface, and Microcontrollers to meet the requirements of handheld Digital Multimeter designers.

Featured Parts

• ADC161S626 – 16-Bit, 50 to 250 kSPS, Differential Input, MicroPower ADC
• ADS8319 – Precision 16-Bit SAR w/ SPI interface in MSOP-10
• INA226AIDGSR – Industry’s most accurate current shunt amplifier
• LMK04828 – Ultra Low Jitter Synthesizer and Jitter Cleaner
• LPV521 – Nanopower, 1.8V, RRIO, CMOS Input, Operational Amplifier
• MSP430FG4616 – Ultra-Low power 16-bit microcontroller offering 512KB Flash, USB interface, 12-bit ADC, dual DAC’s, 160 segment LCD driver
• MSP430F67791 – Ultra-Low power 16-bit microcontroller offering 512KB Flash, 7 independent 24-bit Sigma Delta ADC’s, 320 segment LCD driver
• TMP112AIDRLR – Most accurate temperature sensor for drift compensation

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