Range in a multimeter

Question

I'm an Electric Engineering student and I have my first lab tomorrow. One of the questions in the prelab asks you to give the scales and the range of each scale in your multimeter. Here's mine

I want to know if the range is something like 20 – 200kΩ for the 200kΩ scale and then 0,2 – 20 MΩ for the 20MΩ scale or 0 – 200kΩ for the 200kΩ scale and then 0 – 20 MΩ for the 20MΩ scale.

I know it's something super basic but the information I have is very vague. Thanks for your help.

EDIT: Woah! Thank you all for your time and knowledge, it's a shame I can't even upvote.

Answer 1

All scales start at zero and full scale is printed at the dial. However keep in mind that the resolution of the 200kΩ range is probably 100Ω at best and using that range there is no way you can see the difference between a 50Ω and a 150Ω resistor due to the low resolution. If you switch to the 200Ω range you can easily measure 1Ω difference. Same goes for all the other ranges. Just remember that you want to use the range that matches the measured value closest, to get the most accurate measurement.

Once you get more familiar with measurement equipment you'll learn about errors. Full scale error, error based on magnitude of lowest significant digit, linearity, ... But that all is for a later date.

Answer 2

The meter will typically read to zero on the ohms ranges.

You should not use it on an unnecessarily high range, because the resolution of the reading and the accuracy will, in general, be lower than necessary. So if there is a usable lower range, it's usually better to use it.

For example, you have a resistor marked 15K, you'd want to measure it on the 20K range, so the meter shows 15.0K rather than on the 200K range so the meter would show 015K.

You can find the manual here, and the accuracy specifications for resistance are given below:

So, in the example I gave, the accuracy is +/-0.8% + 2 digits on either range. The uncertainty on the higher range would be +/-320 ohms, on the lower range it would be +/-140 ohms, so more than twice as accurate.

Answer 3

The different range settings on your meter will give you different levels of precision. The meter can only display a certain amount of characters, and so the different ranges effectively determine how many characters are before or after the decimal point. Your meter probably is able to display a "1", followed by three values from 0-9.

If you look at the DC Voltage ranges, for example, you have 200mV, 2000mV (same as 2V), 20V, 200V, and 500V.

These values are the highest that can be measured. You want to choose the setting that is higher than what you are measuring, and the closest. If you were going to read a 1.5V battery, for example, you would choose 2000mV. It may read back something around 1.567 V.

If you measured the same battery with the 20V setting, you will instead get 01.57 V. Notice that it's still correct, but you don't have the precision.

If you chose the 200V setting, you would get 001.6 V.

The same holds true for the other measurement types. Choose the smallest value that is greater than your target. If you select wrong, it simply won't display a value, and you can select a different range. I hope this helps!

Answer 4

The reading on the dial is the full scale reading, it's the largest value that can be measured on that setting.

Let's say that your meter has 3 1/2 digit resolution.

If you set the selector to the 20V setting, the largest voltage than can be measured is 19.99V. If the voltage is larger than that, the meter will indicate in some way, e.g., by flashing "OL" on the screen, that the voltage is too large so that you can change the setting.

Since the voltage can be negative, the most negative voltage that can be measured is -19.99V so the range is from -19.99V to 19.99V for that setting.

If you set the selector instead to 200V, the largest voltage than can be measured is 199.9V. Set to 2V, the largest voltage is 1.999V.

Similarly for the current settings.

For the resistance settings, the range is from 0 to the largest reading.