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Electronics => Beginners => Topic started by: altaic on March 17, 2016, 10:14:21 pm

Title: Decade voltage dividers in digital test equipment?
Post by: altaic on March 17, 2016, 10:14:21 pm
It seems odd to me that decade voltage dividers are used in digital test equipment-- digital test equipment use ADCs which produce binary, and engineers already have to compute noise based on bits. Plus, multiplying/dividing the result of the ADC by a power of 2 is just a bit-shift operation, which is really simple and low-power. Furthermore, dividing voltage by two with resistors is really easy: just match the resistors, which is easy to high-precision with something like a Wheatstone bridge.

Is there a technical reason behind not using powers of 2, like noise distribution? One would think we'd use some sort of prime series in that case, and omit any multiple of two.

Are precision binary voltage divider networks available? I haven't been able to find even non-precision binary voltage divider networks.

Title: Re: Decade voltage dividers in digital test equipment?
Post by: Vgkid on March 17, 2016, 10:22:31 pm
Never seen any binary voltage dividers, though you could look through the various resistor networks that are availlable.
You can always order some custom ones...
Title: Re: Decade voltage dividers in digital test equipment?
Post by: danadak on March 17, 2016, 10:44:53 pm
R-2R ladders used extensively in DACs, and early SARs.

https://www.google.com/imgres?imgurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fimage497.gif&imgrefurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fel3.htm&docid=dGxyx3UXocLTfM&tbnid=8w3EHrowjsAC4M%3A&w=1168&h=616&ei=QTPrVs-6FMSy-AHh-afwBA (https://www.google.com/imgres?imgurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fimage497.gif&imgrefurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fel3.htm&docid=dGxyx3UXocLTfM&tbnid=8w3EHrowjsAC4M%3A&w=1168&h=616&ei=QTPrVs-6FMSy-AHh-afwBA)

Regards, Dana.
Title: Re: Decade voltage dividers in digital test equipment?
Post by: altaic on March 18, 2016, 12:01:29 am
Quote from: danadak on March 17, 2016, 10:44:53 pm
R-2R ladders used extensively in DACs, and early SARs.

https://www.google.com/imgres?imgurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fimage497.gif&imgrefurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fel3.htm&docid=dGxyx3UXocLTfM&tbnid=8w3EHrowjsAC4M%3A&w=1168&h=616&ei=QTPrVs-6FMSy-AHh-afwBA (https://www.google.com/imgres?imgurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fimage497.gif&imgrefurl=http%3A%2F%2Fwww.dnp.fmph.uniba.sk%2F~kollar%2Fje_w%2Fel3.htm&docid=dGxyx3UXocLTfM&tbnid=8w3EHrowjsAC4M%3A&w=1168&h=616&ei=QTPrVs-6FMSy-AHh-afwBA)

Regards, Dana.

Ah, thanks. For some reason I only associated resistor ladders with DACs, but of course they are used for Flash ADCs (and, I take it, early SAR ADCs).