jleblanc: sustainability: Multimeters

Using Multimeters

This page is about helping you use the multimeters at ITP (that's the main kind we have here in the shop pictured on the left). It shows how to set up the Multimeter and what to do with your circuit if you want to measure Resistance, Voltage, or Amperage. In the table below, the image on the left shows how to configure your multi-meter. These are images of the main kind of multimeter at ITP, though it should be helpful for any multimeter. The Image on the right shows how to use the multimeter in your circuit so that you are sure you are actually measuring what you think you are! A more detailed look at the entire face of the multimeter shown on the left can be seen here. Another very useful tutorial is an internet video from Make Magazine that shows how to use a multimeter. This video is here on Youtube. Thanks to Tom Igoe for the link.

. . Before looking at the tables below, a quick note on the scale on the dial range. If you look at the Resistance Range, at the bottom of the range you see the number 200. This means that if the dial is set here, the meter can measure from 0-200 Ohms. If the resistance of the component is above that, the display will read simply 1 . In that case raise the dial to the next higher setting, continuing until you get a good reading.
. . This is true for using the multimeter for measuring voltage and amperage as well. For Resistance and Voltage, if you do not know the right range, pick a low one and then work up until you get a good reading.
. . For Amperage, do the opposite, start high with the red plug in the 10ADC hole (see the tables below). If the Amperage is lower than 200mA, you can switch to the plug on the far right and use the more precise dial settings. If you don't do this, you could blow out a fuse that protects the lower ranges and damage the meter.


When the dial setting number is followed by either a 'm', a 'k', or a 'M' here is what that means:

'm' means Milli, or thousandths (1/1000). This means that if you have the dial at a setting such as 20m for Amperage and the screen says 10, it means the meter is measuring 10mA, or 0.01A.

'k' means Killo, or thousands (1000). This means that if you have the dial at a setting such as 20k for Resistance and the screen says 10, it means the meter is measuring 10K ohms, or 10,000 ohms.

'M' means Mega, or millions (1,000,000). This means that if you have the dial at a setting such as 2M for Resistance and the screen says 1.5, it means the meter is measuring 1.5M ohms, or 1,500,000 ohms.

NOTE that some multimeters do not have ranges, only a single dial setting for Resistance, Voltage and Current. These are called auto-ranging multimeters.

A quick and very important note on measuring Amperage. Make sure that you first measure using the 10A setting. If you see that the Amperage you are pulling is lower than 200mA, use the more sensitive setting.
	Same as the diagram above