Digital Multimeters convert analog measurements and display digital values. DMM's provide better accuracy and resolution than analog meters. Some Fieldpiece DMM's feature an uncalibrated analog bargraph display to mimic the sweeping needle capability of an analog meter.
Digital multimeters have evolved to include more measurements and features. First, think about your application: home, hobbyist, professional electrician, electronics or HVAC technician, etc. Fieldpiece multimeters are designed with HVAC technicians in mind. As such, Fieldpiece multimeters are exclusively handheld digital units. Some feature True RMS measurement, CAT ratings up to IV, and up to 3.75 digit display.
You might consider getting a second meter such as a clamp meter or even a pocket multimeter however with the Fieldpiece modular stick meter system this isn't neccessary. You can buy just one meter and add attachments later. Many attachments are also capable of taking wireless measurements.
Next consider these features
Basic Measurements
Fieldpiece meters are capable of measuring AC/DC Voltage, AC/DC Current, and Resistance. Make sure the meter you are interested in can support the voltage/current ranges you will be working with; certain Fieldpiece meters do feature autoranging functions. Before looking at other features make sure the meter covers your ranges from min to max.
Also, don't forget about any additional measurements you may need, such as:
-
Capacitance (F)
-
Frequency (Hz)
-
Temperature
Safety, Safety, Safety!
When choosing a multimeter, first determine CAT levels you will be operating in. Then choose a meter with a voltage rating higher than the maximum voltage you will be testing at each CAT level. Within a category, a higher voltage rating denotes a higher transient withstand rating, e.g., a CAT III-1000 V meter has superior protection compared to a CAT III-600 V rated meter. The real misunderstanding occurs if someone selects a CAT II-1000 V rated meter thinking that it is superior to a CAT III-600 V meter. Select a meter with the voltage rating suitable for the location (i.e. CAT I, II, III, IV) where you will be operating.
![CAT Rating Diagram]() |
Fluke's
"ABCs of Multimeter Safety"
explains CAT ratings and the standards for each category
Click photo to download the Application Note |
Accuracy and Resolution
-
Focus on the accuracy of the basic measurements Volts and Amps.
-
True RMS (root mean square) refers to the conversion process of the sinusoidal AC current signal into the displayed digital value. True RMS meters, while more costly, provide much better measurement; Fieldpiece offers several True RMS multimeters. TRMS meters calculate an accurate reading even when they encounter irregular waveforms such as square, sawtooth, or rectified waves.
Then consider the extras...
-
Detachable Display is available for some meters. Fieldpiece offers its modular approach with Fieldpiece "Stick Meters" designed for HVAC/R professionals. These meters can be combined with any Fieldpiece meter head attachment to effectively create a manometer, clamp meter, DMM, and anemometer, to name a few, from only one meter. This saves you money and space in your toolkit.
In this video Russ from Fieldpiece breaks down one of the company's True RMS, autoranging stick meters that works with the modular expansion system. Check it out below:
-
Clear big digits for visibility and backlight. You will appreciate it next time you are in low-visibility conditions.
-
Min/Max/Peak Hold. Free you hands and eliminate the need to watch the display closely by capturing min/max/hold at the touch of a button.
-
Continuity. Usually depicted as a button such as this
![continuity_icon]()
. Very useful to determine if a wire or circuit has a break. Complete circuits, or simply touching leads together will give a loud beep. Some meters do a better job at this feature than others with faster response and higher volume. See David Jones video blog below for a demonstration.
-
Temperature Measurement. This can be a very convenient feature to have and a must for HVAC technicians. Includes K type T/C bead wire, IR thermometer or both.
-
Build Quality. Meters above $100-200 will have better durability, fit and finish. The rotary dial will feel better and not permit landing in between settings. Probes will be insulated with silicone instead of PVC, some have CAT ratings printed right on the leads. Probe handles are bigger and tips sharper. Watch the comparison videos below.
Digital Multimeter Accuracy And Resolution Discussion
![countsVSdigits]() |
Snapshot from David Jones Video Blog.
About 3/4ths into the video is an explanation of
DMM counts, digits, accuracy and resolution.
Below is the synopsis and some background
definitions to understand counts, digits,
resolution, and accuracy.
And do watch his complete video below. |
What are Digits on a multimeter?
Digits refers to the resolution of the DMM, not the accuracy. It is common to see meter specifications with 3-½, 3-¾, 4-½, etc. digit display. The half means the most significant digit can go up to 1. It originated because of 7-segment LCD/LED displays. All 7 segments are needed to display every digit. When for the most significant digit on the far left only 1 is to be displayed, only the two rightmost segments of the 7 are needed, hence the term ½ digit originated (i.e. a fraction of the 7 segments are used, very loosely approximated as a half). That was when most DMMs had a maximum reading of 1999. Recently more accurate DMMs became available, having readings up to 2999, or 3999, even 4999, so it became more complicated. Fieldpiece, for example, currently offers multimeters rated up to 3999 counts at 3.75 (3 3/4) digit resolution. Manufacturers have since started using the ¾ approximation but it still isn't very clear as you can see here:
|
Digits |
Display |
|
3 |
+/- 0 through 999 |
|
3-½ |
+/- 0 through 1999 |
|
3-¾ |
+/- 0 through 3999 (typically), but can also mean 2999 or even 4999 |
|
4-½ |
+/- 0 through 19999 |
What are Counts on a multimeter?
Counts are a better way to represent display resolution. Let’s go back to the table.
|
Digits |
Display |
Counts |
|
3 |
+/- 0 through 999 |
1000 |
|
3-½ |
+/- 0 through 1999 |
2000 |
|
3-¾ |
+/- 0 through 3999 (typically) |
4000 |
|
4-½ |
+/- 0 through 19999 |
20000 |
Use of Counts eliminates the fractional confusion of the Digits terminology
So what happens as the measurement goes up in value?
For example, a 3-½ digit, 2000 count meter is measuring 1.999 volts. Increasing the voltage to 2.532 volts results in a loss of the least significant digit. The display will read 2.53 Volts. One digit of resolution is lost.
What about Multimeter Accuracy?
Accuracy is not the same as resolution. Resolution as explained above has to do with the number of visible digits (i.e. to the right of the decimal). Accuracy has to do with how correct or true the value is compared to a standard value from NIST or other international body. Look back at the snapshot from the video blog of David Jones above. He gives a simple formula using counts to give a rough minimum accuracy. David warns against meters that have a published accuracy higher than the minimums on his chart for the count level. See the video in full below.
Quick Question: I often see an accuracy specification like this 1% of reading + 3 counts (or digits). How can I tell what my margin of error would be?
A: It refers to the least significant digit on the meter on that range. As an example, lets work the math for measuring 120 volts ac on a 6000 count meter (remember, it therefore goes from 0 to 5999). To measure 120 volts ac, the meter will have to be on the 600.0 ac voltage range. The resolution (least significant digit) then is 0.1 volt. (120 V X 1% = 1.2 V + 3 digits) = (1.2 V + 0.3 v). Therefore the margin of error would be +/- 1.5 V.
Video blogger David Jones (EEVBlog.com ) “Digital Multimeter Buying Guide for Beginners” has 100,000+ views. He covers safety, accuracy, ruggedness, important to obscure features, takes apart popular models, and more in his colorful and funny style.
This 30 min Fluke Electrical Measurement Safety video gives life saving advice when using meters. In the Meter testing tab, poorly designed meters are tested and shown sparking even catching fire compared to properly designed and fused meters . It really illustrates the importance of not only having the proper CAT rating, but checking that the meter has independent safety approvals such as UL. If you do not see the approval in the data sheet, check the instruction manual, or ask our sales team.
Fieldpiece Multimeter Accessories to consider
Test Leads. The most popular accessory for multimeters are test leads. Test leads do wear out. They should periodically be inspected. Set your meter to ohms and continuity. Then press the tips of the test leads together between your thumb and index finger. resistance should be zero, but wiggle the test leads and watch the display for an O.L. or high resistance. It might indicate that the lead wires inside the sheath are breaking. Leads are not repairable. replace them.
Alternate test leads styles are available from banana, alligator, hook, and more. They make making measurements easier and more accurate.
![caution-for-TL]()
Alternate test leads styles are available from banana, alligator, hook, and more. They make making measurements easier and more accurate.
Current Clamp Adapters. While having a separate current clamp meter may be more convenient, current clamp adapters are available for DMM's.
Temperature Probes. Meters with temperature option will usually come with a bead wire K type thermocouple, but as accessories you can purchase others pipe clamp mounting for measuring pipe surface temperatures, penetrating probes for meats and other foods, and many other styles.
Multimeter Temperature Probe Adapter. If you did not purchase a multimeter with temperature capability, all is not lost. You can purchase temperature modules as accessories that will accept a temperature probe.
Cases and Holsters. Protect your investment.