Author Topic: Voltage "divider" after PSU to highten the resolution?  (Read 5152 times)

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Offline FriedMuleTopic starter

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #25 on: February 21, 2019, 01:45:22 pm »
Calvin yes they du fit better but it looks to me as if only the M8851 do have 0.1mV adjustable resolution.
Am I reading wrong?
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Online rstofer

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #26 on: February 21, 2019, 07:54:52 pm »
The easiest way to handle these kinds of experiments is to pick a voltage that is 'about right' and measure it with a DMM.  Get as close as you can to the desired value.  Do the experiment while measuring everything with DMMs, preferably simultaneously.  All meters should be calibrated annually - and we KNOW that won't happen!  So, all of this supposed accuracy isn't traceable - it is pretty much meaningless but we carry on...

We pick another voltage nearby and measure again.  We rinse and repeat until we have enough points to make a graph.

It's a matter of choosing the tool.  A high resolution power supply is pricey and unless it is of the 4 lead Kelvin type of connection, the power leads voltage drop won't be included in the readings.  A DMM, OTOH, measures right at the load.  It doesn't care about voltage drops in the leads.  And it can measure voltage and current.  Some can do it simultaneously but they too are high $ items.  Current measurements change the associated voltage measurement due to voltage drop in the meter's shunt resistor.  So, measure the voltage after the current measurement.

High resolution DMMs are cheaper than high resolution PSs.  That's good because you need two or three of them.


 

Offline FriedMuleTopic starter

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #27 on: February 21, 2019, 09:13:18 pm »
LOL yes, we all hope and believe that we are reaching precision even when all our meters do not agree completely.
What I hope is not to measure by what value a component do what, but more find out what it does, to do that, I'd need small steps, even if these steps may not be counted precisely. Not much luck in water your plants, if you only have a fire hose! :-)
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Offline Calvin

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #28 on: February 22, 2019, 09:10:01 am »
Hi,

You might ask yourself, how come they state such high resolution, but ripple figure is more than a decade higher?
Ands still You haven´t told us why You think You ´need´ that high resolution in first place

regards
Calvin
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Offline tggzzz

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #29 on: February 22, 2019, 09:38:32 am »
I have a standard power supply with 10mV resolution and max 30V, what I need is a far better resolution.
My first thought was just to put two resistors on the output as a voltage divider, i.e. 1,000:1 but that would also reduce max voltage to 0.03V and that's fare less then the 10V I want and is wary inefficient!!

Is there an other way to increase the resolution by adding some circuit between the PSU and DUT?

You need to state why you need those features - the best answer will vary depending on your requirements.

I rather like my Power Designs 2020 PSU: 0-20V in 1mV steps, plus a pot for tweaking down to 10uV. Low noise too, since the internal reference is an LM399 :)

Good luck finding one, though. I'm not selling mine :)
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Offline FriedMuleTopic starter

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #30 on: February 22, 2019, 10:10:23 am »
I am sorry that I have not been clear on why I think a 0.1mV would be great.
I already have a standard Korad 10mV supply and is normally fine for just delivering stable power, but I am becoming wary interested in how components, chips and circuits are behaving under different voltages and 1mV is to big steps, it's almost like the Korad.


tggzzz could you please tell me how you have made your 2020 PSU, sounds like what I need? :-)
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Offline beanflying

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #31 on: February 22, 2019, 10:34:41 am »
Power Designs are a bit of a 'Relic'  ;) If you want serious control then buy a DC voltage Calibrator  >:D

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Offline tggzzz

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #32 on: February 22, 2019, 11:28:51 am »
I am sorry that I have not been clear on why I think a 0.1mV would be great.
I already have a standard Korad 10mV supply and is normally fine for just delivering stable power, but I am becoming wary interested in how components, chips and circuits are behaving under different voltages and 1mV is to big steps, it's almost like the Korad.

How. Much. Power.? 1uW, 1W, 1MW? There's a big difference between each of those.

Quote
tggzzz could you please tell me how you have made your 2020 PSU, sounds like what I need? :-)

https://www.ebay.co.uk/sch/i.html?_nkw=%22Power+Designs%22++precision

Be aware some Power Designs PSUs are 115V only. With the 2020 it is only necessary to change the transformer taps; soldering required.

Manuals, including schematics are available free on the web.
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Offline jackthomson41

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #33 on: February 22, 2019, 02:12:52 pm »
Power Designs are a bit of a 'Relic'  ;) If you want serious control then buy a DC voltage Calibrator  >:D

eBay auction: #401701628039


How much does it cost ?? I am thinking of designing one using PIC Microcontroller.
« Last Edit: March 10, 2021, 01:26:56 am by jackthomson41 »
 

Online ebastler

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #34 on: February 22, 2019, 02:16:46 pm »
 

Offline ArthurDent

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #35 on: February 22, 2019, 03:32:39 pm »
HP made several precision bench power supplies like the Power Design one pictured above starting in the 1960s and a lot of those are still around and working just fine today. They frequently show up on eBay. Here is a picture of my HP 6111A outputting 20.00005 VDC
« Last Edit: February 22, 2019, 05:05:11 pm by ArthurDent »
 

Offline FriedMuleTopic starter

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Re: Voltage "divider" after PSU to highten the resolution?
« Reply #36 on: March 06, 2019, 04:23:42 pm »
Great idea to get a DC voltage Calibrator, I can se that the one in the picture da have 500mA.
I have looked on ebay but I cant seem to find out the max current, or if I do, they look to be max 50-100mA, and that is maybe a bit to low.
Anyone who know great DC voltage Calibrator with about 500-1,000mA?
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