We started an investigation after hearing from a customer in South East Asia. He said that weighing indicators were quickly breaking, even after several replacements, and that one had broke after 2 weeks just recently.
However, the so-called quickly broken indicator was one of our long-selling items and not easily broken. When such cases occur, the cause is often peculiar to the location. However, this site was overseas and not easy for us to visit so we asked the customer to send us a connection diagram.
I soon received an extremely hard-to-read scan of a ragged diagram that looked like it was from some ancient text. What’s more, it was in Japanese. It appeared to be for a scale that had been assembled by a Japanese company around 20 years ago and then exported overseas.
While it was very hard to make out the diagram, I found the notation “Power cord 2P” while zooming in on it. “Power cord 2P” means an AC power connection with only two pins and no ground pin. I thought, “Well, there’s your problem!”
Certainly, a weighting indicator will run without a ground pin and many consumer electronics have a power cable with only two prongs.
However, unlike consumer electronics, weighing indicators have a number of long cables, including the load cell cable, and they are sometimes connected outdoors.
As a result, if an ungrounded indicator receives noise voltage such as a lightning strike or static electricity, the voltage will pass through the electric circuits inside the weighing indicator and damage them.
While many Japanese homes have 2-pin AC outlets, offices and factories commonly have 3-pin outlets with a ground terminal. Unfortunately, most people ignore grounding because they know from experience that devices will work without it.
I urge anyone reading this article who uses a desktop computer to check that it is properly grounded.