September 2004
In keeping with our string of editorials on communications, note
that we are not making fun of people, or bashing people, we are just pointing
out problems with human nature that keep our systems from running optimally.
If everyone (including us) would stop and reflect then perhaps we could all have
better operations.
We have noticed another phenomenon where some people can not figure out what is wrong. You can tell them exactly what is wrong and what to do about it, but they still won't do it! The problem is -- they refuse to listen.
Unfortunately this happens all the time in automation.
We had one customer that would call us out about every two months to look at an intermittent controls problem. Intermittent problems are very hard to find but you have to start with the basics first -- noise, grounding, and loose connections. If all that checks out then you go through the logic.
But we had designed this system so we knew the logic was good :-). But the mechanical people that built the system never installed any noise filters on the variable frequency drives. There were two VFDs just tied to the main power line (through circuit breakers).
Every time we would come out, look it over, and suggest that they install EMI filter to help isolate the drives. They never did it. However, they even went through the trouble to make electrical noise tests and confirmed our suspicions that the noise levels were very high. But yet they never installed EMI filters!
Every two months, we got called out, we poked around, suggest EMI filters, got our check and left. Finally, they called us out to help them install EMI filters.
Two months went by and we didn't get another call. So we called them. Nope, hadn't had a problem since.
This is another way of saying "You can lead a horse to water but you cannot make him drink."
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