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A voltmeter measures voltage and nothing else. A multimeter is an instrument that contains a voltmeter alongside an ammeter, an ohmmeter and usually continuity, capacitance, frequency and temperature. So the difference is category: one is a function, the other is a box that holds that function among others. The part worth knowing is that the two can disagree on the same two points, because a meter has to draw a little current to measure at all, and how much it draws, its input impedance, changes what it reads on a long cable running beside a live one.
One is a function, the other is a box full of functions
Historically a voltmeter was a distinct object: a moving coil movement with a multiplier resistor in series, calibrated in volts, with a sensitivity quoted in ohms per volt. A 20,000 ohms per volt movement on its 10 volt range presents 200,000 ohms to the circuit. That number was printed on the instrument because it mattered, and it is the ancestor of the input impedance figure on a modern data sheet. Digital instruments made the measuring core generic. A single analogue to digital converter with a programmable front end can measure volts, then shunt current into a known resistance to measure amps, then drive a known current through an unknown resistance to measure ohms, and a rotary switch chooses which. That is all a multimeter is.
The naming has gone loose as a result, and retail listings are the worst offenders. Instruments sold as multimeters sometimes measure one quantity in two ranges, and instruments sold as testers sometimes do more than a general purpose meter. Two cases on this site show the gap between the name and the function, in the VEYFIY solar panel tester review and the ELEJOY solar panel tester review, where the headline numbers and the bullet figures do not agree with each other. Read the function list, never the noun on the box.
Input impedance is the difference that bites
To register a voltage, a meter must let a small current flow through its own front end. Input impedance describes how small. Most handheld digital meters present about 10 megohms on the voltage ranges, which means that at 230 volts the meter draws roughly 23 microamps. That is low enough to leave almost any circuit undisturbed, which is exactly what you want when probing electronics.
It is also what produces ghost voltage. Run a disconnected conductor for twenty metres in a trunking beside an energised one and capacitive coupling will put a voltage on the idle conductor. There is no real source behind it and it can supply almost no current, but a 10 megohm input does not load it, so the display shows something like 80 volts on a cable that is switched off. Deliberately low input impedance solves this by giving the induced charge somewhere to go, and the voltage collapses. The Fluke 116 HVAC multimeter states low input impedance precisely for this purpose, to help prevent false readings due to ghost voltage, alongside a built in thermometer covering minus 40 to 400 degrees Celsius and a microamps range for flame sensor work. That is a multimeter built around one trade and the reading errors that trade keeps meeting.
The trade is real and runs both ways. A low impedance input loads a genuine high impedance source as well as a phantom one, so it is the wrong setting for electronics. This is why some meters offer both as selectable modes rather than picking one, and why a meter with only a high impedance input will keep showing you voltages that are not there.
Counts, digits and what a volt reading can resolve
Resolution and accuracy get conflated constantly, and they are separate specifications. Counts state how many steps the display can show before it has to change range. A 6000 count meter on a 600 volt range resolves 0.1 volt steps. A 55000 count meter on the same decade resolves 0.01 volt steps. Digits say the same thing differently: 5.5 digits means five full digits plus a leading digit with a restricted range, and the exact ceiling depends on the design.
Accuracy is a separate claim, normally written as a percentage of the reading plus a number of least significant digits. The percentage scales with the measurement and the digits term does not, which is why a small reading on a large range is proportionally far worse than the headline figure suggests. Here is what four published listings commit to.
| Instrument | Stated display resolution | Stated basic DC voltage accuracy | Percentage term at a 230 V reading |
|---|---|---|---|
| Fluke 116 HVAC | Not stated in the listing bullets | Not stated in the listing bullets | Cannot be derived from the bullets |
| Fluke 177 | 6000 counts, 4 updates per second | Not stated in the listing bullets | Cannot be derived from the bullets |
| Labloot LB1041 | 55000 counts, dual line display | 0.05 percent | About 0.12 volt |
| Fluke 8808A | 5.5 digits, dual display | 0.015 percent | About 0.035 volt |
The two blank rows are the lesson. A handheld meter can publish its resolution and leave its accuracy unstated, and resolution without accuracy tells you how many digits the display will confidently show you, not how many of them are true. The Fluke 177 states 6000 counts, a 33 segment analogue bar graph updating 40 times a second, hold and auto hold, and minimum, maximum and average memory, which is a feature list rather than an accuracy claim. The Labloot LB1041 bench meter states 55000 counts with DC voltage accuracy up to 0.05 percent, true RMS AC voltage and current, 1000 point internal recording and SCPI support. The Fluke 8808A states 5.5 digit resolution, basic DC voltage accuracy of 0.015 percent and a four wire resistance technique. In all three cases the digits term of the accuracy specification is Not stated in the listing bullets, so the table column above is the percentage part only, and the true error at a small reading will be larger. On the alternating side there is one further specification that decides whether a reading means anything at all, and what is true RMS on a multimeter covers it.
Where a dedicated voltmeter still earns its place
- Panel and permanent installation, where one quantity has to be displayed continuously and a rotary switch is a liability.
- Two pole voltage indicators for proving dead, which are built with low impedance inputs and no range switch so there is nothing to set wrongly.
- Teaching and demonstration, where the loading effect of the instrument is the point being shown.
- Any situation where the measurement must not depend on an operator selecting the right mode under pressure.
Everywhere else the multimeter has won, and for a reason that has nothing to do with voltage: most faults are diagnosed by moving between quantities. You check volts, then continuity, then resistance, then current, and a single instrument that does all four without being swapped out is simply faster. When the current is the quantity of interest and breaking the circuit is not an option, the jaw replaces the probes, and multimeter vs clamp meter covers that division.
Reading a specification sheet instead of a product name
Ignore the noun. Ask what quantities the instrument measures, what input impedance it presents on the voltage ranges and whether that is selectable, what its counts or digits are, what accuracy it claims and over what range, and what safety category it is rated to. Any instrument that answers all five is specified, whatever it is called. Any instrument that leaves accuracy or safety category blank has already told you something, and the one specification never printed on the front of the case, input impedance, is the one most likely to make you chase a voltage that was never there.
Frequently Asked Questions
Can a multimeter replace a voltmeter?
For almost all work, yes, because the voltage function of a multimeter is a voltmeter. The exceptions are panel instruments that have to display continuously, and situations where a deliberately low input impedance is needed to reject induced voltage.
What is ghost voltage?
A reading on a conductor that is not actually energised. A long cable running beside a live one picks up voltage capacitively, and a high impedance meter draws so little current that it displays that induced voltage as though it were real. A low impedance input loads it away.
Why is ten megohms the usual input impedance?
It is a compromise. High enough that the meter barely disturbs most electronic circuits, low enough to be achievable with ordinary components and stable over temperature. It is a design choice, not a law.
Do counts mean the same as accuracy?
No. Counts describe how finely the display can divide a range, which is resolution. Accuracy describes how close the number is to the true value, and it is quoted separately as a percentage of reading plus a number of least significant digits.
Is a bench multimeter better than a handheld?
It is more precise and less portable, and usually not rated for the electrical environment of a consumer unit. Precision and safety category are independent specifications, and bench instruments optimise the first.