Bench Power Supply Readout Drifts

Discussion in 'General Electronics Chat' started by G-ManX, Mar 20, 2016.

  1. G-ManX

    Thread Starter New Member

    Jan 14, 2014
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    I am using one of those cheap generic Chinese bench power supplies from eBay (Model 3010D) which is a 30V 10A DC supply. I normally would have stayed away but it was seriously marked down due to a minor crack in the faceplate which I easily fixed with epoxy.

    This unit turned out to be fairly reliable aside from the LED display which starts out accurate enough, but then over time drifts upwards consistently after being dialed in and left alone. Interestingly the actual voltage output remains perfectly stable and quite usable irrespective of what may be displayed on the LED display. As well, the Current (Amps) LED display reads correctly.

    As a workaround I have wired up 2 cheap multimeters (one to monitor current and the other for voltage), but I would like to see if any of you folks know anything I could adjust internally to get the actual LED readout back on track and stay on track. If not, maybe at least someone could explain what causes such a consistent drift in the readout of these cheap supplies.

    I haven’t timed it, but it appears the voltage readout increases by consistent increments over consistent time period - for example an increase of 1 full volt per every 10 minutes of use. Keep in mind the actual voltage output remains at 1 volt (or whatever I originally set). Any help is greatly appreciated.

    P.S. This issue is the same with and without a load.
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    Could be a resistor problem in voltage divider of the LED meter.
     
    Last edited: Mar 20, 2016
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I guess a schematic won't be forthcoming from the manufacturer. Can you reverse-engineer the voltage sensing part?
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
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    Not a good idea to leave an ammeter connected unless it's in the feedback loop so output voltage can compensate for meter voltage drop.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Take some pictures of it, you maybe better getting a ready made voltmeter module on ebay, plenty of choice.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    3,229
    I suspect the cheap Chinese voltmeter used a poor voltage reference device in the circuit.
    Whatever the case, it likely will be difficult to fix.
    Easier would be just to buy a new, cheap voltmeter to fit and hope it is more stable.
     
    RamaD likes this.
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Drifting over time is almost certainly a thermal problem. Probably as Wally suggested, a voltage reference is drifting as the temperature inside the case warms up. Clearly not the same reference as used for the regulators, a good thing. The two displays might be independent modules with their own internal references.

    ak
     
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