Handheld Digital Multimeter

Former Member — Tue, 12 Apr 2011 14:31:01 GMT

Current Revision posted to Documents by Former Member on 4/12/2011 2:31:01 PM

Instrumentation & Measurement Solutions -
Handheld Digital Multimeter

Multimeters are mainly used to measure resistance, as well as DC/AC voltage and current. Common multimeters can be divided into two types, desktop and handheld digital multimeters depending on their sizes. Desktop digital multimeters are usually used in labs for high-precision measurement and instrument calibration. Handheld digital multimeters are battery-powered devices, often used for on-site debugging. In recent years, handheld digital multimeters have gained tremendous improvement in measurement precision.

A handheld digital multimeter is basically composed of Analogue Front End (AFE), MCU, Human-machine interface and Power supply. The design of handheld multimeters should focus on the features of low power, high performance and compact size.

After a measurement function is selected by the switch, the AFE can start to collect input signals and convert them into digital signals in order to feed into the MCU for processing. http://uk.farnell.com/jsp/bespoke/bespoke7.jsp?bespokepage=common/en/technology-first/applications/instrumentation-measurement/handheld-digital-multimeter.jsp#When measuring resistance, the AFE provides a proper current generated by the inside resistance I-source so that the voltage detected on the measured object is within the input range of the ADC. The detected voltage is amplified and converted into digital signals for data processing by MCU.

When measuring AC current, a current shunt is selected to convert the AC current flowing through it into AC voltage. This voltage is converted by the RMS-to-DC converter into a DC voltage, which is then amplified and converted into digital signals for data processing by MCU.
When measuring DC current, another current shunt is selected to convert the DC current flowing through it into a DC voltage. The DC voltage is then amplified and converted into digital signals for data processing by MCU.
When measuring AC voltage, high voltage input is attenuated while low voltage input remains unchanged. And then it is converted by the RMS-to-DC converter into DC voltage, which is then amplified and converted into digital signals for data processing by MCU.
When measuring DC voltage, high voltage input is attenuated while low voltage input remains unchanged. And then it is amplified and converted into digital signals for data processing by MCU.

The MCU controls measurement processes and implements real-time calculations such as averaging and unit conversion for sampled data. The human-machine interface generally includes a display, several functional keys and a switch for selecting measurement functions. An entry-level handheld digital multimeter usually uses a 7-segment LCD, while a high-end multimeter may have a 1/4 VGA OLED. An isolated power supply is adopted in this solution to implement battery management and power conversion to drive different functional blocks.

APPLICATION NOTES

Manufacturer	Product Type	AN Title	AN Number	URL
ANALOG DEVICE	Amplifier	Low Noise Amplifier Selection Guide for Optimal Noise Performance	AN-940	Click Here
ANALOG DEVICE	RMS to DC	RMS-to-DC Converters Ease Measurement Tasks	AN-268	Click Here
ANALOG DEVICE	RMS to DC	RMS-to-DC Converters	MT-081	Click Here
ANALOG DEVICE	Digital Isolator	ESD/Latch-Up Considerations with iCoupler® Isolation Products	AN-793	Click Here
LINEAR TECHNOLOGY	Data Conversion	“Easy Drive” Delta-Sigma Analog-to-Digital Converters Cancel Input Current Errors	DN368	Click Here
LINEAR TECHNOLOGY	Data Conversion	How to Use the World’s Smallest 24-Bit No Latency Delta-SigmaTM ADC to its Fullest Potential	AN80	Click Here
LINEAR TECHNOLOGY	Data Conversion	Amplifier Selection Guide for Optimum Noise Performance	DN355	Click Here
TEXAS INSTRUMENTS	Amplifier	Noise Analysis In Operational Amplifier Circuits	slva043b	Click Here
TEXAS INSTRUMENTS	Data Conversion	What Designers Should Know About Data Converter Drift	sbaa046	Click Here

WHITE PAPERS

TEXAS INSTRUMENTS	Microcontroller	Push Performance and Power Beyond the Data Sheet	Click Here
TEXAS INSTRUMENTS	Microcontroller	Serial Wire Debug—Ideal for Microcontrollers	Click Here
TEXAS INSTRUMENTS	Microcontroller	MSP430F21x1 Architecture Summary	Click Here
TEXAS INSTRUMENTS	Microcontroller	The ultra-low-power USB revolution	Click Here
TEXAS INSTRUMENTS	Power	Digital power supply considerations for the analog engineer	Click Here

EVAL KITS

Manufacturer	Product Type	Evaluation Kits Title	EVKs Part Number	Part Number	URL
OLIMEX	Microcontroller	MSP430F149 DEVELOPMENT BOARD	MSP430-P149MSP430-P149	MPS430F149	Click Here
OLIMEX	Microcontroller	MSP430F1611 DEVELOPMENT BOARD	MSP430-P1611MSP430-P1611	MSP430F1611	Click Here
OLIMEX	Microcontroller	MSP430F169 DEVELOPMENT BOARD	MSP430-P169MSP430-P169	MSP430F169	Click Here
OLIMEX	Microcontroller	MSP430F249 DEVELOPMENT BOARD	MSP430-P249MSP430-P249	MSP430F249	Click Here
TEXAS INSTRUMENTS	Microcontroller	LM3S2965-IQC50-A2LM3S2965-IQC50-A2 Evaluation Kit with Code Composer Studio	EKS-LM3S2965EKS-LM3S2965	LM3S2965-IQC50-A2LM3S2965-IQC50-A2	Click Here
TEXAS INSTRUMENTS	Microcontroller	LM3S3748-IQC50-A0LM3S3748-IQC50-A0 Evaluation Kit with Code Composer Studio	EKS-LM3S3748EKS-LM3S3748	LM3S3748-IQC50-A0LM3S3748-IQC50-A0	Click Here
TEXAS INSTRUMENTS	Microcontroller	LM3S1968-IQC50-A2LM3S1968-IQC50-A2 Evaluation Kit with Code Composer Studio	EKS-LM3S1968EKS-LM3S1968	LM3S1968-IQC50-A2LM3S1968-IQC50-A2	Click Here
TEXAS INSTRUMENTS	Microcontroller	MSP430F5438 Experimenter Board	MSP-EXP430F5438MSP-EXP430F5438	MSP430F5438	Click Here
TEXAS INSTRUMENTS	Microcontroller	MSP430FG4618/F2013 Experimenter Board	MSP-EXP430FG4618MSP-EXP430FG4618	MSP430FG4618/F2013	Click Here

TRAINING

NATIONAL SEMICONDUCTOR	Amplifier	LMP827x/LMP223x/LMP7721 Precision Amplifiers	LMP827x/LMP223x/LMP7721	Click Here
NATIONAL SEMICONDUCTOR	Data Conversion	Settling Time Challenges and Improvement Techniques in Precision Signal Path Conversion	ADC122S101CIMM/NOPBADC122S101CIMM/NOPB, ADC161S626	Click Here
TEXAS INSTRUMENTS	Amplifier	OPA376: Precision, Low Noise, Low Quiescent Current, Operational Amplifier	OPA376	Click Here
TEXAS INSTRUMENTS	Microprocessor	Lowering the Power Consumption of your Design		Click Here
TEXAS INSTRUMENTS	Microprocessor	Ultra-Low Power MSP430 - The World’s Lowest Power MCU	MSP430	Click Here
TEXAS INSTRUMENTS	Microprocessor	MSP430 MCU Optimization for Ultra-Low Power	MSP430	Click Here
TEXAS INSTRUMENTS	Microprocessor	MSP430 Ultra-low Power Microcontroller Overview	MSP430	Click Here
TEXAS INSTRUMENTS	Voltage Reference	Precision Voltage Reference, Low Noise, Very Low Drift		Click Here

Handheld Digital Multimeter

Handheld Digital Multimeter

Instrumentation & Measurement Solutions -Handheld Digital Multimeter

Instrumentation & Measurement Solutions -
Handheld Digital Multimeter