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Milliohm Meter vs Standard Multimeter: Can a Normal DMM Measure Low Resistance?

A multimeter's resistance range is a convenience feature, not a metrology tool. This explains the physics that limits it, the arithmetic that shows why, and the practical workarounds when you do not own a milliohm meter.

By the Akermin Editorial Team · 8 min read

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A standard multimeter cannot measure milliohms. Its two wire resistance range includes the resistance of its own test leads, the probe contact points and any solder or oxide at the joint, and those parasitics are typically larger than the resistance you are trying to read. The display may have a 0.1 ohm or 0.01 ohm least significant digit, but resolution is not accuracy. A dedicated milliohm meter solves this with four wire Kelvin sensing, which passes current through one pair of leads and senses voltage across another pair, so the lead resistance cancels. If you need to measure ground rod resistance, winding resistance, busbar joints or contact resistance, a purpose built instrument such as a three pole ground resistance tester is the correct tool; a general purpose DMM is the wrong class of instrument for that job.

What the resistance range on a handheld multimeter actually measures

Every handheld digital multimeter measures resistance by pushing a small known current through the device under test and measuring the voltage that appears across it. Ohm’s law then gives the resistance. The circuit is two wire: the same pair of leads carries the test current and senses the voltage. That is fine for reading a 10 kΩ resistor, because the lead resistance of a fraction of an ohm is negligible against 10,000 ohms. It is useless for reading a 10 milliohm joint, because the leads and contacts are themselves tens or hundreds of milliohms.

The listing for the allsun pocket multimeter states a 3 1/2 digit LCD with a maximum reading of 1999. That is a display count, not an accuracy statement. A 1999 count meter on its lowest resistance range typically has a least significant digit of 0.1 ohm. Even if the electronics were perfect, the smallest change it can show is 0.1 ohm, which is 100 milliohms. The resistance you are trying to measure in low resistance work is often smaller than one display step.

Higher specification handhelds do better on paper. The Fluke 116 HVAC multimeter is built for HVAC work and its listing emphasises temperature and microamps for flame sensors rather than low resistance resolution. The listing does not publish a resistance resolution or accuracy figure, so no number can be attributed to it here. The general point stands: a general purpose DMM is designed around voltage, current and continuity, and its resistance range is a secondary function.

The arithmetic that shows why two wire measurement fails at milliohm level

Suppose you want to measure a busbar joint that should be 0.5 milliohms. You connect a two wire meter. The meter reads the joint plus both test leads plus both probe contact resistances plus the contact resistance between probe tip and metal. A typical probe contact is 10 to 50 milliohms depending on pressure, surface oxide and tip condition. A one metre lead is roughly 20 to 30 milliohms of copper. The sum is easily 50 to 150 milliohms, which is 100 to 300 times the value you are trying to read.

Now suppose the joint deteriorates to 5 milliohms. The two wire reading moves from, say, 80 milliohms to 85 milliohms. That is a change of about six percent on a display whose resolution may be 100 milliohms. The fault is invisible. This is the core reason a standard multimeter is the wrong instrument for joint resistance, winding resistance, fuse resistance, contact resistance or ground continuity.

Measurement Typical magnitude Two wire DMM suitability
Resistor on a bench 1 kΩ and above Good
Continuity check Under a few ohms Adequate as go or no go
Busbar joint Sub milliohm to a few milliohms Not suitable
Motor or transformer winding Milliohms to a few ohms Not suitable for the low end
Ground rod resistance Ohms to tens of ohms Requires a dedicated tester

The table is a general guide to magnitudes, not a specification of any product listed here. Where a product listing does not publish a resistance range or resolution, no figure is given.

How four wire Kelvin sensing removes the lead resistance

A milliohm meter uses four terminals, often called a Kelvin connection. Two terminals drive a known current through the sample. The other two sense the voltage across the sample only. Because the sense circuit draws almost no current, the voltage drop across the current leads and their contacts does not appear in the sensed voltage. The meter computes resistance from the sensed voltage and the known current, and the lead resistance cancels mathematically. This is the same principle used in precision shunt measurement and in battery internal resistance testers.

The practical consequence is that a four wire instrument can resolve tens of microohms with ordinary leads, because the leads are outside the measurement. A two wire instrument cannot, no matter how many digits its display has. This is why the answer to the question is not about display counts or resolution figures. It is about topology. If you want background on the instrument class, see milliohm meters for low resistance testing.

Some bench multimeters offer a four wire resistance mode. That is a genuine milliohm capability, but it is a bench instrument, not a handheld. A handheld DMM with a two wire resistance range, however good its voltage accuracy, does not have this capability.

Where the standard multimeter is still the right tool

None of this means a multimeter is a bad instrument. It means the resistance range has a floor. For voltage, current, continuity, diode test and temperature, a handheld DMM is the correct and often the only sensible tool. The HiLeDiQJ digital multimeter listing states measurement up to 600 V AC/DC, 10 A DC current and 2 MΩ resistance, with continuity, diode and triode test. Those are the functions a general purpose meter is built for. The resistance ceiling of 2 MΩ is stated; the resolution at the low end is not stated in the listing bullets.

For ground resistance specifically, a standard multimeter cannot measure it at all in the field. Ground resistance requires either a fall of potential test with auxiliary stakes or a clamp method, and the instrument must inject a signal without tripping protective devices. The Ideal three pole ground resistance and voltage tester listing states the three pole fall of potential method, operation on energized circuits without tripping ground fault breakers, and auto ranging across resistance ranges. That is a different instrument class from a DMM, and it is the one the job requires. For general guidance on meter use, see how to use a multimeter.

For HVAC work, the Fluke 116 is designed around temperature and microamp flame sensor measurement, which are the quantities that HVAC diagnostics actually need. Its listing does not claim milliohm resolution, and it should not be expected to provide it.

Workarounds when you do not own a milliohm meter

There are honest workarounds, and they all involve accepting reduced confidence. The first is a four wire bench measurement, which is the real solution if the sample can be brought to the bench. The second is a constant current source and a separate sensitive voltmeter, which is a manual Kelvin setup and requires care with thermal EMF. The third is a comparative method: measure a known good joint and a suspect joint with the same leads and the same probe pressure, and look for a difference. The absolute number will be wrong, but a large relative difference can still reveal a fault. This is a screening method, not a measurement.

The fourth is to use the continuity beeper as a go or no go test and accept that it says nothing about milliohms. The fifth is to use a battery internal resistance tester or a dedicated low resistance ohmmeter if that is the quantity of interest. What you should not do is read a two wire DMM display to three decimal places and believe the last two digits. For related distinctions, see multimeter vs clamp meter and what true RMS means on a multimeter.

The maintenance and technique issues nobody mentions

Probe tip condition matters more than most buyers expect. Oxidised, pitted or dirty tips add contact resistance that varies with pressure and angle. On a two wire meter this directly corrupts the reading. On a four wire meter the current contacts still matter for current delivery, but the sense contacts carry almost no current, so their contact resistance matters far less. Keeping tips clean and using firm, consistent pressure is basic technique for any resistance measurement.

Thermal EMF is the second issue. Dissimilar metals at a junction generate a small voltage, typically microvolts per degree Celsius of temperature difference. In a four wire measurement at the microohm level, that voltage can be a significant fraction of the sensed signal. Good milliohm meters offer a current reversal or offset compensation feature. A two wire DMM has no such feature, which is another reason it cannot be trusted at the low end.

Lead resistance is the third. Even on a four wire meter, the current leads must be adequate for the test current, and long thin leads add resistance that limits the current the instrument can drive. The listing for any given product may not publish lead resistance, and if it does not, the phrase is Not stated in the listing bullets. For the difference between a voltmeter and a multimeter, see voltmeter and multimeter difference.

The short answer, restated

A standard multimeter’s resistance range is a convenience for reading resistors and checking continuity. It is not a milliohm instrument. The two wire topology puts lead and contact resistance in series with the sample, and at milliohm levels those parasitics dominate. A dedicated milliohm meter, or a four wire bench measurement, is the correct tool for low resistance work. For ground resistance, a purpose built tester such as the Ideal ground resistance tester is the right class of instrument. For HVAC diagnostics, a meter built around temperature and microamps such as the Fluke 116 is the right choice. Use each instrument for the quantity it was designed to measure, and do not ask a general purpose DMM to resolve a milliohm.

Frequently Asked Questions

Can I measure milliohms with a standard multimeter if I zero the leads?

Zeroing or relative mode subtracts a fixed lead resistance, which helps a little, but it cannot remove contact resistance that changes with pressure, temperature or oxide, and it cannot improve the display resolution below its least significant digit. On a 1999 count meter the lowest resistance step is typically 0.1 ohm, which is 100 milliohms. Zeroing does not create resolution that the instrument does not have.

What is the lowest resistance a typical handheld DMM can measure meaningfully?

It depends on the model, and most listings do not publish a low resistance accuracy figure. As a general rule, a two wire handheld DMM is meaningful for readings of a few ohms and above. Below that, lead and contact resistance dominate. If a listing does not state a resolution or accuracy at the low end, the figure is Not stated in the listing bullets.

Does a four wire multimeter exist in handheld form?

Four wire resistance measurement is common on bench multimeters and dedicated milliohm meters, and rare on handheld DMMs. Some specialist low resistance ohmmeters are portable and use four wire Kelvin clips. A general purpose handheld DMM with a two wire resistance range does not have this capability, regardless of its display count.

Can a standard multimeter measure ground rod resistance?

No. Ground resistance measurement requires a fall of potential test with auxiliary stakes or a clamp method, and the instrument must be designed to inject a signal without tripping protective devices. A standard DMM cannot perform this measurement. A dedicated tester such as the Ideal three pole ground resistance and voltage tester is the correct instrument class.

Is a milliohm meter the same as a microohmmeter?

The terms overlap. Both refer to low resistance instruments, and the distinction is usually one of resolution and current capability rather than a hard boundary. What matters for the buyer is whether the instrument uses four wire sensing and what current it can drive. A two wire DMM is neither a milliohm meter nor a microohmmeter.

Why does my multimeter show a nonzero reading when I touch the probes together?

That reading is the resistance of the leads and the contact between the probe tips. It is normal and it is exactly the parasitic that makes two wire milliohm measurement impossible. If the reading is unstable or high, clean the tips and check the leads. On a four wire instrument this contact resistance is largely cancelled by the sense circuit.