Ohmmeter

measuredtwo-terminal (2T) sensing
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current.wikipedia
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Measuring instrument

instrumentscientific instrumentinstruments
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current.

Electrical resistance and conductance

resistanceelectrical resistanceconductance
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current.
An instrument for measuring resistance is called an ohmmeter.

Megger Group Limited

MeggerAVOEvershed & Vignoles Ltd
Megohmmeters (also a trademarked device Megger) measure large values of resistance.
Three other products were also nominated: hand-held micro-ohmmeter MOM2 (category Innovative Power Product of the Year), professional portable appliance tester PAT400 (Innovative Test & Measurement Product of the Year), and digital earth clamps DET14C / DET24C (Innovative Commercial/Industrial Product of the Year).

Multimeter

digital multimeterdigital multimetersDMM
Ohmmeters of this type only ever measured resistance as they could not easily be incorporated into a multimeter design.
A multimeter is the combination of a DC voltmeter, AC voltmeter, ammeter, and ohmmeter.

Four-terminal sensing

Kelvin sensingKelvin connectionfour terminal measurement
This four terminal measurement technique is called Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances.
Four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the simpler and more usual two-terminal (2T) sensing.

Megohmmeter

Megohmmeter or megger is a special type of ohmmeter used to measure the electrical resistance of insulators.

Electronic test equipment

test equipmentelectronic test instrumentelectrical test equipment

Kelvin bridge

This four terminal measurement technique is called Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances.
Resistors above about 1 ohm in value can be measured using a variety of techniques, such as an ohmmeter or by using a Wheatstone bridge.

Ammeter

microammetermoving coil meterampere-meter
This type of meter movement is extremely common for both ammeters and other meters derived from them, such as voltmeters and ohmmeters.

Electricity

electricalelectricelectrically
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current.

Electric current

currentelectrical currentcurrents
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current.

Omega

ΩOmega (Ω)ω (omega)
The unit of measurement for resistance is ohms .

Galvanometer

D'Arsonval galvanometertangent galvanometernull detector
These were similar to the galvanometer type movement encountered in later instruments, but instead of hairsprings to supply a restoring force they used conducting 'ligaments'.

Voltage

potential differenceVvoltages
Subsequent designs of ohmmeter provided a small battery to apply a voltage to a resistance via a galvanometer to measure the current through the resistance (battery, galvanometer and resistance all connected in series).

Series and parallel circuits

seriesparallelin series
Subsequent designs of ohmmeter provided a small battery to apply a voltage to a resistance via a galvanometer to measure the current through the resistance (battery, galvanometer and resistance all connected in series).

Analog-to-digital converter

ADCanalog to digital converteranalog-to-digital conversion
These measurements are then digitized with an analog digital converter (adc) after which a microcontroller or microprocessor make the division of the current and voltage according to Ohm's Law and then decode these to a display to offer the user a reading of the resistance value they're measuring at that instant.

Microcontroller

microcontrollersMCUmicro-controller
These measurements are then digitized with an analog digital converter (adc) after which a microcontroller or microprocessor make the division of the current and voltage according to Ohm's Law and then decode these to a display to offer the user a reading of the resistance value they're measuring at that instant.

Microprocessor

microprocessorsprocessorprocessors
These measurements are then digitized with an analog digital converter (adc) after which a microcontroller or microprocessor make the division of the current and voltage according to Ohm's Law and then decode these to a display to offer the user a reading of the resistance value they're measuring at that instant.

Ohm's law

ohmicOhmohmic losses
These measurements are then digitized with an analog digital converter (adc) after which a microcontroller or microprocessor make the division of the current and voltage according to Ohm's Law and then decode these to a display to offer the user a reading of the resistance value they're measuring at that instant.

Current divider

current divisioncurrent divider rulereduced output
This is partly because the change in deflection itself is small when the resistance measured is too small in proportion to the intrinsic resistance of the ohmmeter (which can be dealt with through current division), but mostly because the meter's reading is the sum of the resistance of the measuring leads, the contact resistances and the resistance being measured.

William Thomson, 1st Baron Kelvin

Lord KelvinWilliam ThomsonWilliam Thomson, Lord Kelvin
This four terminal measurement technique is called Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances.

Electronics

electronicelectronic equipmentelectronic device