In this video, Barron Stone discusses using a DMM, or digital multimeter. Learn why a DMM is an indispensable tool for working with electronics. Understand the various modes and measurement functions.
- When working with electronics, a multimeter is the go to tool for testing and troubleshooting circuits. It's your first line of defense for tracking down problems. A multimeter is a single device that can measure a variety of electrical quantities, and most modern multimeters have a numeric display like this one, so they're called digital multimeters, or DMM. You can buy a DMM at most hardware or electronics stores, or from an online retailer like SparkFun or Amazon.com. There's a wide range of multimeters available from different manufacturers, that vary in capabilities.
When choosing a DMM, at the very least make sure it can measure voltage, current, resistance, and electrical continuity. This is a basic DMM, which only measures those four necessities. I bought it from SparkFun.com, which sells it as a low-cost, entry-level model. So, if you're a beginner hobbyist on a budget, then a DMM like this one should serve you well. If you want to get something with a bit more capability, I would recommend a DMM like this Extech MN36, which I borrowed from my wife.
In addition to the four basic DMM measurements, it can also measure capacitance, frequency, and temperature, plus it has the nice ability to automatically set the range for measurements so you don't have to. I've included a document called DMM List.pdf, which includes information about both of these DMMs, in the exercise file for this video. You should choose a DMM based on your budget and needs. I'll be using the DMM from SparkFun, because it's adequate for what I need to measure throughout this course.
There are three main parts to this DMM. At the top is the display, where I'll read the value for my measurement. Below that is the selector knob, which I'll use to choose the type of measurement I want to measure; voltage, current, resistance, or continuity. When I'm not using the DMM, I always keep this knob in the off position to save on the battery. At the bottom on the DMM are three ports that I'll use to connect my probe. These are basic needle test probes, which are typically colored red and black. There's no difference between the probes, other than their color, but the black probe is conventionally attached to common ground, or negative reference within a circuit, and then the red probe is used to check voltages at other points throughout the circuit.
The probes for this multimeter use a type of connector called a banana connector, because the plug supposedly looks kind of like a banana. This type of connector is common amongst multimeters, and allows you to attach a variety of different types of probes. Now, I have two probes, but there are three ports on the DMM. So, which port should I connect each probe to? The black probe is the simplest. Since I'll usually be connecting it to the common ground for voltage measurements, I'll attach the black cable to the port labeled com, which stands for common.
This leaves me with two options for the red probe, and I almost always use the port on the right for milliamps, volts, and ohms. I'll connect the probe to this port for all the voltage and resistance measurements, and for smaller current measurements that are less than 200 milliamps. This other port is specifically designed to measure larger current up to 10 amps. I rarely ever use that port, and for this course, I'll only be making measurements that require the red probe to be connected to the right side.
- Comparing conductors and insulators
- Relating electric current to flowing water
- Exploring Ohm's law
- Measuring DC voltage
- Measuring direct current
- Calculating the power consumption of your circuits
- Choosing the right batteries to power your circuits