PRISM Forum - Message Replies

Posted by: Sue Hedrick (shedrick@advanced-control.com )
Organization:ACC
Date posted: Wed May 3 16:43:04 US/Eastern 2006
Subject: Resistor calculation
Message:
With regard to resistor calculations, how can I determine theta EC. I had thought that it was calculated using (storage temp - max operating temp) / resistor power rating. This gives me huge numbers, greater than 600 deg C / W. What should I be doing? Thanks, Sue

Subject: Resistor Temperature/Temperature Rise
Reply Posted by: David Dylis (ddylis@alionscience.com )
Organization: System Reliabilitye Center (SRC)
Date Posted: Thu May 4 10:47:56 US/Eastern 2006
Message:
In lieu of actual information, I would recommend using the PRISM default. Appendix G of the PRISM User Manual includes defaults for resistor temperature rise. These defaults vary based on the type of resistor being used. Defaults are as follows:

Resistor, Fixed, Carbon Composition: Temperature Rise = 20
Resistor, Fixed, Carbon Film: Temperature Rise = 30
Resistor, Fixed, General: Temperature Rise = 30
Resistor, Fixed, Metal Film: Temperature Rise = 30
Resistor, Fixed, Network: Temperature Rise = 30
Resistor, Fixed, Thermistor: Temperature Rise = 0
Resistor, Fixed, Wirewound: Temperature Rise = 20
Resistor, Variable: Temperature Rise = 25
Resistor, Variable, Film: Temperature Rise = 25
Resistor, Variable, Non-Wirewound: Temperature Rise = 20
Resistor, Variable, Trimmer, Composition: Temperature Rise = 20
Resistor, Variable, Wirewound: Temperature Rise = 0
Resistor, Varistor: Temperature Rise = 50

If you have additional questions, feel free to contact me.