Editing Multimeter (section)

=== Resolution ===
The resolution of a multimeter is the smallest part of the scale which can be shown, which is scale dependent. On some digital multimeters it can be configured, with higher resolution measurements taking longer to complete. For example, a multimeter that has a 1&nbsp;mV resolution on a 10&nbsp;V scale can show changes in measurements in 1&nbsp;mV increments. Absolute accuracy is the error of the measurement compared to a perfect measurement. Relative accuracy is the error of the measurement compared to the device used to calibrate the multimeter. Most multimeter datasheets provide relative accuracy. To compute the absolute accuracy from the relative accuracy of a multimeter add the absolute accuracy of the device used to calibrate the multimeter to the relative accuracy of the multimeter.<ref name="Keithley Instruments">{{cite web|title=Model 2002 Multimeter Specifications|url=http://www.keithley.com/data?asset=5799|publisher=Keithley Instruments}}</ref>

The resolution of a multimeter is often specified in the number of decimal [[Numerical digit|digits]] [[Sensor resolution|resolved]] and displayed. If the most significant digit cannot take all values from 0 to 9 it is generally, and confusingly, termed a fractional digit. For example, a multimeter which can read up to 19999 (plus an embedded decimal point) is said to read {{frac|4|1|2}} digits. By convention, if the most significant digit can be either 0 or 1, it is termed a half-digit; if it can take higher values without reaching 9 (often 3 or 5), it may be called three-quarters of a digit. A {{frac|5|1|2}}-digit multimeter would display one "half digit" that could only display 0 or 1, followed by five digits taking all values from 0 to 9.<ref>{{cite web|url=http://zone.ni.com/devzone/cda/tut/p/id/3295|access-date=2008-01-26|title=Digital Multimeter Measurement Fundamentals|publisher=National Instruments}}</ref> Such a meter could show positive or negative values from 0 to 199999. A {{frac|3|3|4}}-digit meter can display a quantity from 0 to 3999 or 5999, depending on the manufacturer. While a digital display can easily be extended in [[display resolution|resolution]], the extra digits are of no value if not accompanied by care in the design and calibration of the analog portions of the multimeter. Meaningful (i.e., high-accuracy) measurements require a good understanding of the instrument specifications, good control of the measurement conditions, and traceability of the calibration of the instrument. However, even if its resolution exceeds the [[accuracy and precision|accuracy]], a meter can be useful for comparing measurements. For example, a meter reading {{frac|5|1|2}} stable digits may indicate that one nominally 100&nbsp;kΩ resistor is about 7&nbsp;Ω greater than another, although the error of each measurement is 0.2% of reading plus 0.05% of full-scale value. Specifying "display counts" is another way to specify the resolution. Display counts give the largest number, or the largest number plus one (to include the display of all zeros) the multimeter's display can show, ignoring the [[decimal separator]]. For example, a {{frac|5|1|2}}-digit multimeter can also be specified as a 199999 display count or 200000 display count multimeter. Often the display count is just called the 'count' in multimeter specifications. The accuracy of a digital multimeter may be stated in a two-term form, such as "±1% of reading +2 counts", reflecting the different sources of error in the instrument.<ref>Stephen A. Dyer, ''Wiley Survey of Instrumentation and Measurement'', John Wiley & Sons, 2004 {{ISBN|0471221651}}, p. 290</ref>

[[File:Multimeter-4269.jpg|thumb|Display face of an analog multimeter]]

Analog meters are older designs, but despite being technically surpassed by digital meters with bar graphs, may still be preferred{{according to whom|date=March 2020}} by engineers{{which|date=March 2020}} and troubleshooters.{{original research inline|date=March 2020}} One reason given is that analog meters are more sensitive (or responsive) to changes in the circuit that is being measured.{{citation needed|date=March 2020}} A digital multimeter samples the quantity being measured over time, and then displays it. Analog multimeters continuously read the test value. If there are slight changes in readings, the needle of an analog multimeter will attempt to track it, as opposed to the digital meter having to wait until the next sample, giving delays between each discontinuous reading (plus the digital meter may additionally require settling time to converge on the value). The digital display value as opposed to an analog display is subjectively more difficult to read. This continuous tracking feature becomes important when testing capacitors or coils, for example. A properly functioning capacitor should allow current to flow when voltage is applied, then the current slowly decreases to zero and this "signature" is easy to see on an analog multimeter but not on a digital multimeter. This is similar when testing a coil, except the current starts low and increases. Resistance measurements on an analog meter, in particular, can be of low precision due to the typical resistance measurement circuit which compresses the scale heavily at the higher resistance values. Inexpensive analog meters may have only a single resistance scale, seriously restricting the range of precise measurements. Typically, an analog meter will have a panel adjustment to set the zero-ohms calibration of the meter, to compensate for the varying voltage of the meter battery, and the resistance of the meter's test leads.