Jack Ganssle's Blog This is Jack's outlet for thoughts about designing and programming embedded systems. It's a complement to my bi-weekly newsletter The Embedded Muse. Contact me at jack@ganssle.com. I'm an old-timer engineer who still finds the field endlessly fascinating (bio).

The WIRECARE AC Circuit Tester

September 1, 2021

ZeroPlus is an interesting Taiwanese company that makes a great set of logic analyzers, that I have reviewed here and here. They also make other products, and have a subsidiary that makes home devices. They recently sent me their new WIRECARE.

About 20 years ago we were renting a house. An old house. The wiring was perhaps to code, once, but clearly didn't conform to the modern electrical code. I smelled smoke and called the fire department who found nothing wrong. But they were less than happy to see how in the office I had multiple outlet strips plugged into each other to support an engineering lab on the single outlet in the room.

As houses get older all too often their electrical systems don't get upgraded. Very old places may have been refitted with wiring that's external to the walls. Others might use knob and tube wires, which scares me but I'm told is still legal in many jurisdictions. Here's an example:

The WIRECARE is a small device that evaluates the wiring in houses and buildings. It's a pretty simple unit: you plug it directly into an outlet and a series of LEDs flash for a couple of seconds before stabilizing on a color. Red means call an electrician, now; yellow indicates sub-par wiring and green indicates everything is copacetic.

A warning in the manual talks about an internal load resistance and a MOS switch, so I suspect the device puts a low-impedance load on the mains and measures voltage drop. The thing is so small and it does not heat up in use, so the load is probably applied for a very short time.

Update: The Wirecare folks provided me with this useful information:

When we moved into the current house 12 years ago I ran 220 to a new circuit breaker box in the garage and then circuits throughout the room. I plugged the WIRECARE into the circuit physically the most distant from the building's main breaker box and was happy to see it indicate green, an OK message.

Though our house is 50 years old, all of the circuits tested were green. Wanting to see it indicate a problem I connected it to the far end of a 100 foot extension cord that uses 14 gauge wires. And, voila! The WIRECARE's LEDs showed yellow, I suspect as a result of a voltage drop through that long run.

At just $100 the WIRECARE seems like a nice way to be sure your circuits are safe. Especially now that we too often employ outlet strips galore to support our electronics zoo. Available from Amazon. There's more info here.

Feel free to email me with comments.

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