Dear Verpies
The problem with it is getting identical resistors and thermocouples or thermistors with a calibrated thermal loss to ambient and no thermal cross-talk.
We do not worry about loss to ambient, as it is a null balance method, not a quantitative method.
Matching of thermocouples is not necessary if they are cut from the same roll of wire.
Cross talk can be held to a minimum with careful construction. The method is still under construction and many of your concerns have been priorly considered and simple solutions worked out, but not yet posted.
How identical would you consider the resistors need to be?...I have resistors that are 0.02% over the range of interest. There are trimming and compensating methods if need be tighter tolerance.
Measuring input power cannot be done this way because the power dissipated in a resistor connected in series with the input terminals of the DUT is not the same as the power delivered to that DUT.
I already explained that there are two methods to use the bridge, one method connects to the input to the DUT in which case power factor to the DUT is compensated by increasing R1
The other method (manual) is by using a power supply to balance the bridge and noting power required. Such null balance methods are tried and true for over 200 years.
I have used the method with great success over the years, and was only trying to share what I have learned from over 30 years of working in the field of thermocouple thermometry.
Lastly, I am familiar with your circuit, Vasiks circuit and other RF bridge circuits that have been published over the years, but I admit not all of them.
I find this approach works just fine, meets my needs, and solves many problems, but not all.
That's why I wanted to share it with others.
Perhaps I need to make the intent of the thread clearer as
you are well respected by all on this forum including me, and your opinions carry much weight, however your caveats have cast this work in a negative light, and IMO perhaps unfairly.
If it doesn't meet your criteria or you find it objectionable, kindly
disregard and by all means,
don't use it.
You could also petition the administrator to have it removed with the claim that it is technically unworkable.
Regards
P.S. I think I may be wasting my time on this forum trying to be helpful, maybe time better spent elsewhere.
"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
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Topic: Flea Power Measurements (Read 8345 times)
