Ed,
I should add that if the company was starting from scratch, and was just
starting the ISO procedure writing, then the "no cal" way could work smoothly
and be the way to go. But if the company already has hundreds of written
procedures in place then there could be substantial costs to change things. A
cost analysis can be used to determine the payback time. I know of no good way
to determine the "opportunity costs" and I have not seen accountants pay much
attention to this.
Costs up front:
Examining all written procedures
Rewritting some procedures
Engineering change orders to change procedures
Savings that go on forever:
Reduced calibration time and a smaller cal department needed
Less cal lab equipment to buy, maintain, and cal
Less production downtime due to equipment away for calibration
Dave Cuthbert
Micron Technology
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Price, Ed
Sent: Friday, November 07, 2003 2:59 PM
To: '[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
