Gosshhh , I really hate to give Phil hard time ,
but beside of Eric's,
Jim, the ISO inspector WILL ask you for calibration origins of ALL of your
calibrating meters;
if he's worth his salt and pepper.
That includes your wrist watch , or whatever timing device you use.
Don't laugh, they go strictly by the book, no such thing as commoners sense
.
You can ask your telephone time service provider (confirmed time) ;
or hire calibrated (certified) chronometer
(unless you're rich enough for sporting a gas filled SeaMaster under
warranty).
Yes, i know it's stupid, your choice of taking chances .
pk
PS
True Eric, boiled milk in Lhasa is not even pasteurized .
"Make things as simple as possible, but not simpler"
- A. Einstein
-----Original Message-----
From: Eric Kalgren [mailto:[log in to unmask]]
Sent: Friday, 17 December 1999 6:18
To: [log in to unmask]
Subject: Re: [TN] Calibrating re-flow oven
Phil's idea on speed is good, but I have issues with the temperature bit.
Your altitude is going to drastically affect the boiling/freezing point of
water, as will the water's purity. It may be better to talk to the
equipment guys (if you have them) and see what procedure they use to
calibrate thermocouples and use something along those lines.
Eric Kalgren
BFGoodrich Aerospace
Data Systems Division
[log in to unmask]
(505) 938-5139
>>> Phil Zarrow <[log in to unmask]> 12/16/99 11:59AM >>>
Jim -
The simplest approach is the direct approach. Regarding conveyor speed,
mark
off a measured length on the on-load (or off-load) and time how long it
takes
a mark on the conveyor (or a link or pin) to cover the distance. Calculate
the speed and compare it to the setpoint. Most ovens have closed-loop
conveyor speed control but it is a good idea to test it.
The way I used to measure accuracy of temperature was to attach a
thermocouple to the the PDI controller (or you can use the inputs for
on-board profile tracking your oven might have come with) and place the
thermocouple first into a beaker of ice and then into a beaker of boiling
water. The temperature measured by the machine should be 0 deg. C and 100
deg C respectively.
I suppose there are fancier, more "academic" approaches, but this is
practical, simple, economical and can even be incorporated as part of your
ISO-9002 procedures.
Phil Zarrow
ITM, Inc.
Durham, NH USA
www.ITM-SMT.com
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