Gert,
As with Doug's method it would make for an interesting ISPCE/PSES
discussion and paper. Put something together.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 23427
Tigard, ORe 97281-3427
503/452-1201
p.perk...@ieee.org
-----Original Message-----
From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl]
Sent: Sunday, January 8, 2017 7:26 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Thermal equilibrium - 10% rule
Hi Rich,
The quotient of subsequent derivatives of equidistant samples of the
temperature has a direct relation to the time constant.
TC=Timestep/(1-(dtempn+1/dtempn)) Numerically this is easy to calculate in a
spreadsheet Once the time constant is known it is easy to find the temperature
value of the 63.2% of the final temperature.
samples:
time1 - Temp1
time2 - Temp2 (Temp2-Temp1) - -
time3 - Temp3 (Temp3-Temp2) - - dtemp2/dtemp1
time4 - Temp4 (Temp4-Temp3) - - dtemp3/dtemp2
The quotients in the last column are constant for a true inverse exponential
temperature rise curve (same as a RC circuit).
Of course , only for simple constant power heating curves that are truly
exponential.
The third column will quickly show if the curve is exponential or not , if the
quotients are not all the same, something more complex is happening.
I hope this is a clear explanation....
Regards,
Ing. Gert Gremmen, BSc
g.grem...@cetest.nl
www.cetest.nl
Kiotoweg 363
3047 BG Rotterdam
T 31(0)104152426
F 31(0)104154953
Before printing, think about the environment.
-----Oorspronkelijk bericht-----
Van: Richard Nute [mailto:ri...@ieee.org]
Verzonden: zaterdag 7 januari 2017 20:51
Aan: EMC-PSTC@LISTSERV.IEEE.ORG
Onderwerp: Re: [PSES] Thermal equilibrium - 10% rule
> We have to consider that the temperatures sought are not of
> metrological value, but to to establish a safe/non-safe result.
Yes!
> The mathematical limit of an exponential rise is easy to estimate,
> once a few timed samples are available,
I haven't been able to come up with an equation, even though I have tried and
sought help from folks who are more knowledgeable than me in the field of
thermodynamics. Please tell us your methodology.
Best wishes for the New Year!
Rich
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