We live in an electronic world, yet most folks don’t know much about what happens inside the black electronic box. If you want to give students some introduction to electricity and electronics, learning about the basic tools is important.
A multimeter is an essential tool:
The model shown is about $5. There is an explanation sheet when you buy one of these meters, but here are a few pointers about using some basic functions.
Voltage
On the Meter find the DCV scales. For most of your work, the 20 volt scale will be fine. If you are measuring larger voltages, then the 200 250 scales can be used. If small voltages are measured that are less that a volt, then the. 2000 millivolt scale (or, 2 volt scale) can be used. If tiny portions of volts are measured, then the 200 milli volt (.2 volt scale) are available.
Here a nine volt batter is measured on the 2 DCV scale at 8.5 Volts.
We could have used the 200 volt scale, but note the reading is now rounded to 8.5.
The general rule of using meters is to always select the lowest range that can accommodate the voltage as it will be the most accurate.
In this video I show how to measure some cells. I used the 20 Volt scale, but could have used the 2000 millivolt scale (2 volts).
Current
Unlike voltage, current measurement examines the quantity or rate of flow of charge. Measured in amperes, most multimeters have scales that are in the milliampere range.
In the photo below note that the meter must be part of the circuit to allow electron flow through the device. Here we see how much current two small bulbs allow with a 9 volt battery. Note we are on the 200 milliampere scale and the reading therefore is 155.6 milliamperes.
In a second example, an LED is measured in a circuit. Again, the 200 milliampere scale was used although we could have used the 20 milliampere scale owing to the result we see on the meter:
The same cells I measured voltage, I will now test their current capacity.
Resistance. Although there are other interesting things that this meter can do, measuring resistance is the third most common function.
Here is an example of measuring a resistor. The first is a 150 ohm resistor. (If you need a short course on reading resistance codes, see:
There is a great deal more to learn, of course, but these three things will help you make essential measurements for explorations.
Let me know if you feel a bit comfortable with the meter after experimenting: mjaeger@eou.edu