James: Answering for me only.
Perhaps there is a concern that a test lab that also does modifications to the EUT to bring it into compliance, will ALWAYS find that the EUT needs intervention. The customer may be falsely told that the initial test was a failure, the manufacturer then authorize the test house to come up with a fix, the test house waits until the next day and then tells the client that they installed a small filter and that now the EUT is in compliance. And that they will be happy to provide the client with a quote for as many filters as needed. Back around 1968, I developed a relationship with a number of the major hand power tool manufacturers. They were selling electric power tools to the military, and the reigning standard at that time required a CE & RE test on a sample from every sales order. It was common knowledge that unmodified commercial tools always failed the CE & RE, so a set of X & Y capacitors, in a custom metal housing, was needed. I had a standard rate for CE & RE testing of a hand power tool, and my filter cost was pretty similar (a slight variation due to the need for an odd bracket or fitting an odd shape inside the handle). I worked out a deal that I would do an as-is test with official data, apply the appropriate filter, then test again to verify the efficacy of the new filter, and then create a report showing before and after data. The customers liked it because one location could do their testing and also supply competitive filter solutions in very little time. Eventually, since the military would make repeated buys of particular tools (and each needed a test report), the tool manufacturers told me to keep their power tools so that I could pull them off the shelf the next time the manufacturer sold another batch to the military. After a while, the manufacturer would be selling a new version of tool, so they let me keep the old tools. Eventually, I had a very impressive collection of power tools. I was never tempted to not do a test and use old data, nor did I ever gouge them on the filter cost. I was happy to be getting a locked-in job flow and free tools, and the manufacturers got quick service and predictable costs. Maybe it was a simpler time too. Ed Price WB6WSN Chula Vista, CA USA From: James Pawson (U3C) [mailto:[email protected]] Sent: Tuesday, April 23, 2019 12:39 AM To: [email protected] Subject: Re: [PSES] Question re: Measuring a signal in a noisy environment Hi John, Something you wrote earlier has puzzled me a little. I’ve summarised the thread below, hopefully retaining the original context JMW: I doubt anyone would disagree with that. But if a company allows a test house to impose compliance, how can it know that the result is reliable? Ed: I don’t see how a test house can “impose” compliance. I thought all they could do was perform testing, and by looking at the results of the testing, declare compliance. JMW: People take or send an EUT to the test house, which finds that it fails. [The test house personnel] descend on it with ferrites, copper tape, capacitors, unicorn poo (rarely) until it passes. That's what I mean by 'imposing' I’m interested in your use of the word “reliable”. If the modifications applied achieve a “pass” in the test and are then implemented by the manufacturer, in what sense is this not reliable? I’d be interested to hear your thoughts. All the best James James Pawson EMC Problem Solver Unit 3 Compliance www.unit3compliance.co.uk<http://www.unit3compliance.co.uk> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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