# I need explanation on some digital multimeter (DMM) specifications

What is digital multimeter (DMM) ranges reading; resistance : 400 ohm - 40 Mohm supposed to mean? would it mean the DMM cannot measure a material resistive property of less than 400 ohm ?
And what does tolerance 1% rdg. indicate which followed by: 5 dgt mean ? Thanks in advance

What is digital multimeter (DMM) ranges reading; resistance : 400 ohm - 40 Mohm supposed to mean?

It means that the meter has a number of different ranges for measuring resistance, anywhere from 400Ω full-scale to 40MΩ full-scale.

would it mean the DMM cannot measure a material resistive property of less than 400 ohm ?

No. The minimum value of resistance that can be displayed depends on the full-scale range and the number of digits in the display. For example, a "4-3/4 digit" meter on the 400Ω range would have a resolution of 0.01Ω.

And what does tolerance 1% rdg. indicate which followed by: 5 dgt mean ?

This describes the accuracy of the meter, which is a combination of a couple of factors.

• The analog components limit the accuracy to ±1% of the actual value being measured.

• The digital circuitry limits the accuracy to ±5 counts (i.e., in the least-significant digit of the display) of the actual value.

The overall accuracy will be determined by whichever of these two limits is larger.

For example, if you are measuring a 100Ω resistor, the first rule says that the actual value will be between 99Ω and 101Ω, while the second rule says it is between 99.95Ω and 100.05Ω — the first rule applies.

But if you measure a 1Ω resistor, the first rule gives 0.99Ω - 1.01Ω while the second rule gives 0.95Ω - 1.05Ω — in this case, the second rule applies.

• In my answer, I have likely mis-interpreted the "5 dgt" error spec as a 5-digit meter display. Your interpretation of +-5 counts makes much more sense. – glen_geek Jul 9 '17 at 17:24
• This is partly incorrect. Accuracy is typically specified as, for example: +/-(0.25% rdg + 3 dgt). The digitization error is in addition to the analog error -- as it would pretty much have to be. – Brock Adams Jul 9 '17 at 23:50
• @BrockAdams: Fair enough, but it really only makes a difference when the two error sources are approximately equal in magnitude. In all other cases, one or the other completely dominates the answer. – Dave Tweed Jul 10 '17 at 0:37
• FYI another post was recently made referring to this one because they were confused whether they could ignore the count error or not. In their case they could not because although the count error was less than the percent error, they were still similar in magnitude. electronics.stackexchange.com/questions/503502/… – DKNguyen Jun 3 at 18:16

Yes, it will measure a resistor less than 400 ohms. The 400 ohm lower limit likely refers to the full-scale value. Perhaps it is an auto-ranging meter. If so, when resistance is near the top of the range (for example above 300 ohms) it might auto-range to the next scale, which would likely be 4000 ohms.

"1 % rdg" is the reading error. Your displayed resistance could be 1% high or 1% low. This error doesn't include error caused by you contacting the resistor you're trying to measure, and doesn't include the resistance of the meter's leads.
Five digits seems overkill for a meter with 1% error. If you measure a 300 ohm resistor on a 5-digit meter, the display might be "297.32". That's within 1% error, but gives you a false sense of accuracy.

• I'm thankful to you sincerely help others, God blesses you.. Ameen. – klenteed Jul 9 '17 at 22:53