The DVM on Your Wrist

A Wireless Link Between A DVM and a Smart Watch

- By Brian Millier

Finding it getting harder to read the display of his Agilent DVM while holding the probes on boards with modern, small components, Brian reverse-engineered the optical port on the DVM and sent the readings to a TTGO T-Watch on his wrist.

When I retired from my electronics position at Dalhousie University, I lost access to the high-end test equipment I had used there. Since electronics was also my main hobby, I already had a decent DVM and ‘scope, but I decided to splurge a bit and order a better DVM. I chose the Agilent U1232A DVM (now the Keysight U1232A) and was surprised to find 2 port holes on the back of the unit, the purpose of which I was unaware (shown circled in Figure 1).

Looking at the user’s manual, I determined that this was an optically coupled IR interface that would allow you to log the meter’s readings to a computer. This required the purchase of the U1173 IR-USB cable option. Since I don’t really use my DVM for data-logging, I didn’t pursue this option.

Over subsequent years, a lot of use and some display-screen damage (due to dropping it a few times), has made the display somewhat harder to read. In addition, my eyesight is not as good under poor lighting conditions as it once was. I also find that electronic components are made using ever finer lead pitches, and it’s getting difficult to hold the meter probes in place and look at the display at the same time.

While you might consider this a rather off-the-wall project, what I decided to do was design my own version of the U1773 IR-USB interface. to send the DVM readings wirelessly to a smart watch. I figured it would be easier to see the numbers on the backlit smart watch display, which would be on the wrist of the hand that was holding the test probe in place.