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Electronics => Beginners => Topic started by: ert829 on March 07, 2014, 08:09:53 pm

Title: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: ert829 on March 07, 2014, 08:09:53 pm
I have a new lab power supply which has single turn 10K potentiometers on it.  It is difficult to set precise values with these pots.  I would like to replace some them (voltage) with 10 turn 10K pots.  But...I noticed that the minimum resistance on these devices is 100 Ohm, not zero, like I measured on the single turn pots.  I suspect that this will be a problem.  Any thoughts out there?

-ert829
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: uwezi on March 07, 2014, 08:39:15 pm
What's in the specs is not always what you see in reality. It is what the manufacturer is willing to guarantee.

I have not seen a 10-turn pot which would perform worse than a 1-turn pot with regard to lowest resistance.
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: SeanB on March 07, 2014, 08:41:56 pm
If they fit behind the panel just replace them Any 10 turn pot of reasonable quality will have lower end travel resistance than most single turn composition pots. If you need lower resolution look for some 3 turn or 5 turn pots instead, they are shallower.
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: Golana on March 07, 2014, 10:00:02 pm
I would recommend these:

http://www.digikey.com/product-search/en?vendor=0&keywords=3590S-2-103L-ND (http://www.digikey.com/product-search/en?vendor=0&keywords=3590S-2-103L-ND)

I replaced some single turn pots with these on a cheap Mastech power supply and they have been working great for several years.  Minimum resistance is 1Ohm.  They are a bit bulky but if you have room for them they are great quality.
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: plesa on March 07, 2014, 10:20:50 pm
I have a new lab power supply which has single turn 10K potentiometers on it.  It is difficult to set precise values with these pots.  I would like to replace some them (voltage) with 10 turn 10K pots.  But...I noticed that the minimum resistance on these devices is 100 Ohm, not zero, like I measured on the single turn pots.  I suspect that this will be a problem.  Any thoughts out there?

-ert829

The Vishay 534 Spectrol can go down to bellow 0.05 Ohm, measured on 10k.
http://se.farnell.com/vishay-spectrol/534b1103jlb/pot-rotary-10k-20-6mm-5/dp/1144786 (http://se.farnell.com/vishay-spectrol/534b1103jlb/pot-rotary-10k-20-6mm-5/dp/1144786)
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: JOERGG on March 08, 2014, 10:02:09 am
I dropped the idea of inserting a  10 turn pot in my power supply, because i could not find knobs for a 6.35mm axis and thought that it was to expensive to realize later that a 6mm knob will not fit.
Does a 6mm knob fit onto the slightly thicker axis or how did you solve this problem?
Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: Psi on March 08, 2014, 10:12:13 am
I dropped the idea of inserting a  10 turn pot in my power supply, because i could not find knobs for a 6.35mm axis and thought that it was to expensive to realize later that a 6mm knob will not fit.
Does a 6mm knob fit onto the slightly thicker axis or how did you solve this problem?

Search for 1/4" knobs instead  ;)
Trying to find 6.35mm knobs is like trying to find a M6.35 machine screw.

Title: Re: Replace Single Turn Potentiometer with 10 Turn Precision Pot on Lab Power Supply
Post by: JOERGG on March 08, 2014, 10:27:27 am
Search for 1/4" knobs instead  ;)
Trying to find 6.35mm knobs is like trying to find a M6.35 machine screw.
That makes sense, thank you so much, how blind can one be if not to be used to calculate with inches  :-+. I really couldnĀ“t see it.  :palm: