Measuring the effectiveness of a heatsink or the thermal load of a CPU requires thermal test tools. In this episode, learn how an IR Thermometer and a Thermocouple could be used on an electronics workbench. Many multimeters (DMMs) include the ability to measure temperature with a K-type thermocouple. See examples of when each measurement could be used.

Behind the scenes of Thermal Tools Tutorial

Originally intended to use the episode to show how hot the Pi 4 would get. However, by the time I got around to producing it, a new version of Raspbian came out, resolving the temperature issues. To heat up the Pi, I used this toolset from GitHub: XXXXX.

A multimeter is the go-to-tool for electronics measurements. Knowing how to use it to measure voltage, current, diodes, and transistors can save time (and frustration) while troubleshooting. In this video, James explains how the multimeter works, so that you can understand them better. After watching, you will gain a solid DMM basics understanding.

Behind the scenes of wbw’s DMM Basics

The first Workbench Wednesdays episode covered a pen-style DMM. Back when we were first developing the show, the intent was to be more of a review show and less of a tutorial show. That episode became a mix of both. So we decided to do a straight-up tutorial on DMM basics. Measuring voltage usually has not tripped up too many people, especially on an auto-ranging meter. The main thing to remember with current is to move the red lead back to the voltage input immediately after making a measurement. I touched on continuity briefly but hope to come back and cover that more in the future.

After watching this episode, I would recommend moving to the bench power supply tutorial. After a DMM, the bench supply is one of the most used tools.

Bench DMMs have an extra set of banana jacks called “sense.” Known as a Kelvin or 4-wire resistance measurements, these inputs accurately measure small resistors. Like, milliohms small. This video shows how to make a 4-wire measurement, prove when it is accurate, and alternatives to 4-wire.  See below for an explanation of the alternative method shown.

Behind the scenes

Doing yet another DMM episode was a tough call for me. However, I am working on a project that requires me to characterize both a 1 ohm and a 100 milliohm resistor. The element14 community was kind enough to send me an MP720028 bench DMM. As shown in the picture, it has an extra set of banana jacks called “4-wire sense.” These connections make 4-wire resistance measurements. In this video, I show the same resistor measured with the traditional 2-wire and advanced 4-wire configuration. (Spoiler Alert! The 2-wire measurement was almost twice as big as the 4-wire!)

Alternative 4-Wire Resistance Measurement

In the video, I show one optional method of using a multimeter with 4-wire resistance capability. The trade-off is that it requires at least two multimeters. Since the 4-wire measurement is making two measurements at the same time: voltage and current, the alternative method does the same thing. A bench power supply, ideally with current limiting, applies a voltage to the resistor under test (RUT). One multimeter is used to measure the current through the resistor and, another measure the voltage across it.

In a pinch, you could use the bench supply’s ammeter for the current, however, its precision is probably much less than the average DMM. Once the voltage and current are known, a little bit of ohm’s law determines the RUT’s resistance!