Hello All,
In testing some product for excessive temperatures I have come up
against the following problem. Consider a diode (part of a bridge
rectifier circuit) and the PCB underneath the component. If one measures
the temperature of the diode it does not come close to the specification
for the
Kevin,
Good question. By measuring the pad there are several items to consider.
1st, is the thermocouple in electrical contact with the pad? If so, you may
have an incorrect reading caused by currents from the pad through the probe.
2nd, In measuring the pad, you are measuring the junction
Moshe:
One possible source of the phenomenon you've observed could likely be beating
caused by assynchronous clocks. It's even more defined when the frequencies are
slightly skewed by an amount slightly less than your receiver bandwidth.
Take for example, you have two processors running off
Of equal concern for minor excessive temperatures, is that the bond
strength of the copper on the PWB will be the first thing affected. The
copper may pull away from the laminate due to thermal stresses and
eventually result in high impedance connections. Such poor electrical
connections could
Hello everyone,
Could someone please confirm that all commercial aircraft, world-wide, have
North American outlets on board and that the power available at these
outlets is 115 Volts at 400Hz.
Thanks,
Paul Schilke
Advance Machine Company
pschi...@advmac.com
To add to Art Michael's ways used to work around the problem of PCBs
getting too hot, if the heat is being radiated (rather than conducted
through the leads) from the component to the PCB, put a shiny reflective
surface on the PCB (self adhesive aluminium foil, or just an area of
copper on the
We run into this quite often, and yes, I do consider the PCB measurement
to be a valid measurement of the PCB temperature whether you are on a
pad, a trace, or laminate. My experience with agencies is that they
agree, and will allow (for example) a power resistor to be as hot as it's
Good point. Local heating can damage a board locally.
Although people often do not test the way you indicate,
I've seen several failures due to long-term heat aging
of the board under a hot component.
Some things I've done:
1. Space the component body off the board and/or use longer leads to
How about another test case:
A radio transmitter - carrier only. Turn it on. Then measure the RF
output at my local test site.
Does the spectrum analyzer report a constant/consistent amount?
Seems to me we'd need to define fixed emission
Hello Kevin,
This is not an uncommon problem as you have probably guessed. Rather than
get embroiled in discussing the details of what one should measure, I'd
rather offer a couple of ways I've seen used to work around the problem.
A) Assuming you are using leaded diodes; Raise the diode off of
I understand what you mean, but I'm not sure this is the whole story.
I often check a product which is in idle mode, i.e. the processor is running
in a tight loop, repeating itself every X microseconds (which is probably less
than the measurement equipment integration time). In this situation
I understand what you mean, but I'm not sure this is the whole story.
I often check a product which is in idle mode, i.e. the processor is running
in a tight loop, repeating itself every X microseconds (which is probably less
than the measurement equipment integration time). In this situation
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