Digital Multimeter: the History of Evolution


analog meter

Past

digital meter 2Fluke Meter

Present

Smart Tweezers

Future?

Digital Multimeter (DMM) is an electronic measurement device measuring more than one electrical parameter. Digital Multimeters show measured values in numbers, usually on a liquid crystal display. This is in contrast to Analog Multimeters displaying measured values via a dial, typically a moving pointer or needle moving along a scale.

Historically current, voltage, and resistance measurements were standard features for early Digital Multimeters and they were reffered to as AVO meters, that was derived from Amperes, Volts, and Ohms, the units used for the measurement of current, voltage, and resistance.

Modern Digital Multimeters in addition to current, voltage, and resistance can measure also measure Capacitance, Inductance, Quality and Dissipation Factors, Frequency, Temperature, pH Factor, Humidity, etc. Currently one the most popular combinations is an LCR Digital Multimeters, the name derived from standard symbols used for Inductance (L), Capacitance (C) and Resistance (R).

Prices for Digital Multimeters vary from US$20 to US$500 depending on the accuracy and available features.

Accuracy of Digital Multimeters

Earlier Analog Multimeters had basic accuracies of five to ten percent. For modern Digital Multimeters typical accuracy is a bout 1-3% but may may have accuracies as good as ±0.025%, and high-end bench-top instruments can have even higher accuracies better than 0.01%.

Resolution

For a Digital Multimeter, resolution is the smallest change in an input signal that produces a change in the output signal.

Sometimes the resolution of a Digital Multimeter is specified in the number of digits Digital Multimeter could display. A 5½ digit multimeter would have five full digits that display values from 0 to 9 and one half digit that could only display 0 or 1.

Digital Multimeters can be used to troubleshoot electrical problems in a wide array of household devices such as possibly dead batteries, washing and drying machines, kitchen appliances, and even automobile electronics and electrical systems.

Calibration Certificates for Digital Multimeters

Professional quality Digital Multimeters are normally sold with a certificate of calibration indicating the meter has been adjusted to standards traceable to the Institute for National Measurement Standards in Canada or National Institute of Standards and Technology in the USA. Such manufacturers usually provide calibration services after sales, as well, so that older equipment may be recertified.

Digital Multimeter Probes

Typically Digital Multimeters may utilize Crocodile clips, retractable hook clips, or pointed probes as the three most common attachments. The connectors are attached to flexible, thickly-insulated leads that are terminated with connectors appropriate for the meter. Handheld meters typically use shrouded or recessed banana jacks, while bench-top meters may use banana jacks or BNC connectors. Some Digital Multimeters are equipped with a tweezers that allow a one-hand operation when doing measurements.

Smart Tweezers is an example of the ultimate integration of the tweezers and the Digital Multimeter making it an indispensable tool for Surface Mount Technology. As a result of such integration unpredictable parasitic resistance, capacitance and inductance of the probes (including leads) is reduced to a highly predictable offset slightly depending on the distance between the Digital Multimeter’s probes (tweezers’ tips). Effectively this puts Smart Tweezers priced at US$350 into a category of expensive and highly accurate bench Digital Multimeters.

Meters which measure high voltages or current may use non-contact attachment mechanism to trade accuracy for safety. Clamp meters provide a coil that clamps around a conductor in order to measure the current flowing through it.

Precision of Digital Multimeters

Precision is a measure of the stability of the Digital Multimeter and its capability of resulting in the same measurement when repeating measurements for the same input signal or component.

Precision is especially important when a Digital Multimeter is used to calibrate a device or to perform relative measurements.

Smart Tweezers ST-5S

Smart Tweezers

Smart Tweezers are the original tweezer-based LCR/ESR meter. This device debuted in the early 2000's with the ST-1. The latest model is the ST-5S, features include:
  • Automatic and Manual LCR/ESR measurements
  • 0.2% Basic accuracy
  • Component identification and automatic best test parameter selection
  • Automatic best range selection
  • Component sorting with 1, 5, 10, and 20% tolerance
  • Continuity and diode testing
  • Semi-automatic offset-subtraction
  • Lithium-Ion battery with micro-USB charging
  • 1 oz. weight
  • OLED display
  • NIST Traceable Calibration Certificate

LCR-Reader

LCR-Reader

LCR-Reader is a simplified LCR and ESR-meter at a lower price point. This model has less features and a slightly lower basic accuracy.
  • Automatic and manual LCR and ESR measurements
  • Basic accuracy of 0.5%
  • Automatic best test range selection
  • Li-Ion battery with micro-USB charging
  • 1 oz. weight
  • OLED display
  • NIST Traceable Calibration Certificate

 

 


LCR-Reader-MP

LCR-Reader-MP

The LCR-Reader-MP is a multipurpose tester with lots of features and a high basic accuracy.

  • Automatic and manual LCR, ESR, LED/Diode measurements
  • 0.1% Basic accuracy
  • Oscilloscope Transient Voltage display for up to 100 kHz
  • Diode/LED and Continuity testing
  • Two Test Signal levels, Automatic Test Signal Redction to 0.1 V for in-circuit measurements
  • Signal Generator: Sine, Rectangle, Triangle pulse shapes up to 100 kHz
  • AC/DC voltage measurement up to 15 V
  • Frequency, Pulse Period and Duty Cycle up to 400 kHz
  • Easy Short/Open Calibration, Offset Removal
  • Variable Test Frequencies (25, 100, 120 Hz, 1 ,10, 20, 30, 40, 50, 60, 75, and 100 kHz)
  • Displays active and reactive impedance components
  • Li-Ion battery with micro-USB charger
  • 2 oz. weight
  • Backlit display
  • NIST Traceable Calibration Certificate