Fortunately I don't have to contend with ISO 9000 issues, so I cannot authoritatively expound on the proper implementation per that standard.
But from an engineering point-of-view, Ed is precisely correct that stimulus equipment is not calibrated. In fact, it used to be taught in instrumentation classes that you NEVER relied on the power supply/signal generator/ampifier/whatever readout, you used a properly calibrated meter to monitor the desired quantity. Back in those old common sense days, it was common for the meter on a stimulus equipment to have a sticker nearby that said, "For Indication Only." As part of my job I travel a lot witnessing EMI tests at facilities all over the country. It is very rare to see stimulus equipment with a calibration sticker. Sometimes there are stickers that say "Calibration Not Required," and sometimes there is a different sticker that is a place holder instead of a cal sticker, I guess so that every piece of equipment is covered by some "process." I see this not as a technical issue at all but as a contest between engineers and engineer-wannabes, people who either inflict themselves on engineering >from outside the discipline, or engineer washouts who couldn't make it as professional engineers, were side-lined into other professions where they wouldn't cause trouble, but have now come back to haunt. It's the Dilbert principle, and I quote Scott Adams: "The most ineffective workers are systematically moved to the place where they can do the least damage - management." Or in the case of Ed's company, ISO 9000 process owners. I don't want to do a general attachment, but there is a pertinent Dilbert strip for this. Dilbert has been selected to kick-off the ISO 9000 process. He tells the meeting attendees, "Each of you was hand-picked by your manager for this project because... In the last panel you see the brain-dead moronic attendees, and Dilbert finishes his statement from the last panel, "Well... never mind why," 'Nuff said. From: "Price, Ed" <[email protected]> Reply-To: "Price, Ed" <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Fri, 7 Nov 2003 13:58:35 -0800 To: "'[email protected]'" <[email protected]> Subject: Equipment Calibration In some ways, I have the luxury of having a Metrology Department that maintains the periodic calibration on all of my test equipment. OTOH, as a "customer" of this Metrology Department's "product", I would like to have some control over my overhead costs. And my latest bright idea has me getting stomped by the gurus of the status quo. I need to get smarter about how a calibration system works, and how flexible it can be. My lab has about 500 pieces of capital equipment, and the way I see it, all my equipment falls into one of two categories. The first category consists of those instruments which are used to measure the parameters of our company's products, and determine if the performance of those products falls within a range of acceptable tolerance. Data from these measurements is often contractually reported to our customers. Every equipment within this category needs to be maintained on a program of periodic, traceable calibration. But then there's the second category; which consists of support and stimulus equipment. Items here are old analog signal generators, function generators, amplifiers, pulse generators, sweepers and power supplies. To me, none of this equipment needs ANY periodic calibration. I base this on practical usage. Who can accurately read a power supply mechanical 80-amp ammeter that has a 1.5" long scale? Who can set a function generator frequency control that covers 2 decades, logarithmically, in 270 degrees of rotation? If I need to apply a 100 kHz signal in bursts of 2 milliseconds at a 1 Hz rate, I'll use a calibrated, traceable oscilloscope to set the uncalibrated generator to exactly what I need. The same for that power supply; if I need to know the current to 2% or better, I'll use a calibrated resistor and a calibrated DMM. And I couldn't care less about the gain of an RF power amplifier, as long as it pumps out enough power to create the field I need. Now, I'm not trying to justify the use of distorted, unstable or junky equipment. I'm just trying to spend my calibration dollars the most efficient way. And the way I see it, about 1/4 of my equipment fits my definition of not needing periodic calibration because I can monitor the results with calibrated equipment. So I proposed that these items be tagged with some kind of "uncalibrated" or "user verified" or "no calibration required" label. The gurus of Metrology say this can't be done, our ISO9000 Quality System will not allow this. I can't understand how a customer-oriented quality system can't be crafted to meet the needs of all of the customers of that system. And I suppose I'm felling a bit squeezed, what with my customers expecting me to use COTS equipment to function in military environments. I have to get more out of what I have, and the old military concept of everything in sight is on periodic calibration has to yield to current reality. So, am I getting shoveled upon regarding the impossibility of having a category of officially non-calibrated equipment alongside my calibrated equipment? How have you dealt with calibration program costs? Regards, Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty
