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simple impedance bridge question

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neazoi

neazoi

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hi in this bridge (3rd diagram) do both the 27R resistors need to be better 25R?
Also can the 51R be 50R?

Will it be more "accurate" then with the above changes?
 

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neazoi said:
hi in this bridge (3rd diagram) do both the 27R resistors need to be better 25R?
Also can the 51R be 50R?

Will it be more "accurate" then with the above changes?
Click to expand...

The 51 Ohm resistor could well be 50 Ohms anyway. a 10% tolerance is likely to vary from at least 45 to 55 Ohms anyway so you are not likely to gain anything

same for your 27 Ohm resistor .... I personally haven't seen 25 Ohm resistors ... there may be one of the lesser known E series that has a 25 Ohm

Dave
 
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    neazoi

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davenn said:
The 51 Ohm resistor could well be 50 Ohms anyway. a 10% tolerance is likely to vary from at least 45 to 55 Ohms anyway so you are not likely to gain anything

same for your 27 Ohm resistor .... I personally haven't seen 25 Ohm resistors ... there may be one of the lesser known E series that has a 25 Ohm

Dave
Click to expand...

But ideally, the input resistors should be 25R instead of 27R, am I right?
 

neazoi said:
But ideally, the input resistors should be 25R instead of 27R, am I right?
Click to expand...


maybe ideally, but in the real world it isn't likely to happen
consider you have only been looking at the resistor values. What about the tolerances of the inductors and capacitors ?
they will affect the outcome as well. Living with acceptable tolerances is what it is all about
 

do both the 27R resistors need to be better 25R
Click to expand...
Why? The circuit input impedance is far from 50 ohms in either case.

More generally speaking, as long as the concept behind component choice isn't clarified, the values are just arbitrary.
 

Hi,

The circuit input impedance is far from 50 ohms in either case.
Click to expand...
I see two 27 Ohms in series at the input... making 54 Ohms. Then there is a connection between both of them... decreasing overall input impedance a bit.
Is it really far away from 50 Ohms?

I´m talking about circuit "C", left side of picture. OP says "3rd diagram".

Klaus
 
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KlausST said:
Hi,


I see two 27 Ohms in series at the input... making 54 Ohms. Then there is a connection between both of them... decreasing overall input impedance a bit.
Is it really far away from 50 Ohms?

I´m talking about circuit "C", left side of picture. OP says "3rd diagram".

Klaus
Click to expand...

Can you please tell me If I can connect the 10nF capacitor of circuit A, to the same place on circuit B (shunt between the diode and the choke)?
Will it affect the performance of circuit B in a negative manner?
 

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