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esr meter build

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peter g

Member
hi nigel, there are several versions of the software. the reason I picked this one is that it shows three parameters of c.u.t. this is a fairly old project, I would think the designer would have corrected any bugs.
 

Nigel Goodwin

Super Moderator
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hi nigel, there are several versions of the software. the reason I picked this one is that it shows three parameters of c.u.t. this is a fairly old project, I would think the designer would have corrected any bugs.
If it's displaying negative values, then there's certainly got to be a software problem - as it shouldn't be able to do that - who would write a program with the capability of displaying negative values for something which can only ever be positive?.
 

Pommie

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It's probably using itoa(int to asc) function which will display negative numbers. This suggests that it is measuring resistance higher than 32767 which would be a circuit problem.

Mike.
 

peter g

Member
I built three of these meters and they all have the same problem with neg esr readings. the rest of the meter works!
 

ronsimpson

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This suggests that it is measuring resistance higher than 32767
or higher than 127 if 8 bit number.
shows the esr of electrolytic capacitors as a negative value
How about taking a really good 10uF cap or 1uF that we know has low ESR, (non electrolytic) and make certain it works right.
Then solder a 1 ohm resistor in series. (0.1 ohm, or 10 ohm something small) It should read 1 ohm more.
Then increase the resistance a little at a time. I could be that at some value the number flips negative. (What Pommie said)

Can you imagine that anyone could get mixed up about signed/un-signed numbers. LOL
 

peter g

Member
hi ron, o.k. I will do that and post back. btw, in case you haven't guessed my electronic knowledge is limited to fixing TV's.
 

peter g

Member
o.k I got up to 65 ohms display did not turn negative. at 66 ohms the meter stopped reading esr, just a question mark.on a different tack it seems that the esr value to be correct depends a lot on what the Vesr voltage is. when its hi(180 millivolts or more it works)?
 

Pommie

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Most Helpful Member
The meter reads in mΩ and therefor above 32Ω will display as negative. Int to Asc on microcontrollers takes a 16 bit number so it should be above 32767 that is negative.

Mike.
 
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