LPS-1 measurement 'problem'

Kingpin

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Mar 5, 2017
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Recently i did a measurement on the Uptone LPS-1 on ripple and noisefloor.
As Uptone stated it should completely free from 50/60Hz ripple from the AC mains.
The strange thing is that i measure a 50Hz (in my country) ripple (-90dB).
Maybe i picked up a 50Hz at my probe but to clearify i switched the LPS-1 with my LiPo powered Power Supply which is completely free from AC.
The LiPo PS was completely free from a 50Hz ripple at the output, so i can conclude that my probe wasn't pick up any interference noise.
But what could cause the 50Hz ripple at the output of the LPS-1 ?

Did anybody here some measurements on the LPS-1 ?
 

amirm

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I have not seen any measurements of it. If you explain more how you made your measurements I am game for buying a unit and testing it to verify.

The issues I have heard about is noise induced due to bank switching (voltages are not the same so cause a glitch).
 

Kingpin

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Mar 5, 2017
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Test Setup:
Meanwell -> LPS-1 -> 50? resistor -> Spectrum Analyzer


Probe measured as the one on the right picture over the resistor at the end of the LPS-1 dc cable:

f1.jpg


Today i measured again on my work with a PicoScope.
Also here i measured the 50Hz ripple and his harmonics at -90dB.
The only devices which where on the same outlet are a computer/picoscope/Analyzer and the LPS-1(Meanwell)
I kept my probe away from any 230V cables.

I don't have differential probes, so if that should be the problem ? I don't know.
What i know is that when i measure my LiPo powered Supply (no AC) i have no 50Hz ripple, so i think the probe isn't picking up some noise (but i'm not shure of course, but that's my theory).

Therefor i posted the question here because i'm curious if it's my faulty test setup or i do have a device which generates a (little) 50Hz ripple.
 

Kingpin

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Mar 5, 2017
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Found the 'problem'.
It was not the probe but the dc-cord which pick-up some 50Hz noise !

I always measure at the end of a dc cable with a resistor for more reallife presentation instead directly after the regulator smoothing capacitor.
 

jkeny

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Feb 9, 2012
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Found the 'problem'.
It was not the probe but the dc-cord which pick-up some 50Hz noise !

I always measure at the end of a dc cable with a resistor for more reallife presentation instead directly after the regulator smoothing capacitor.

You mean you had the sense resistor at the end of a DC cord - the good probing diagram you posted did not represent your measurement setup?

Well done in chasing down the issue which requires some application & desire to find out the truth - it's a good lesson to learn for the other poster on this thread :)
 

Kingpin

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Mar 5, 2017
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You mean you had the sense resistor at the end of a DC cord - the good probing diagram you posted did not represent your measurement setup?
That's correct, i should have mention that !

Well done in chasing down the issue which requires some application & desire to find out the truth - it's a good lesson to learn for the other poster on this thread :)
Thanks.
 

amirm

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Found the 'problem'.
It was not the probe but the dc-cord which pick-up some 50Hz noise !

I always measure at the end of a dc cable with a resistor for more reallife presentation instead directly after the regulator smoothing capacitor.
Which indeed is how users utilize the unit. By measuring right at the dc terminal you are measuring a scenario that is not in use.
 

jkeny

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That's correct, i should have mention that !


Thanks.

How long is the DC cord - how close to other power cables carrying mains - have you tried other DC cords with what results? Is this the Dc cord you normally use to carry power?
If you are using this DC cord config to emulate real world conditions - have you found a real world solution that obviates these mains harmonics i.e a coaxial cable or such?
 
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jkeny

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Which indeed is how users utilize the unit. By measuring right at the dc terminal you are measuring a scenario that is not in use.

By measuring at the end of a DC cord, he measured device + cord & not device alone. Your continual conflating of these issues doesn't serve you well as a self-appointed "measurement police" & "consumer protector"

He didn't denigrate the device (as you seem you want to do) - he found out what was causing his measurement anomaly - a lesson you might learn someday? BTW do his measurements remind you of any of your own results?

As my follow up post asked - did he stop at this point or continue his investigation to find a "power cable" he could use which doesn't pick up the mains harmonics - it requires some desire for getting to the realistic sit
 

amirm

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By measuring at the end of a DC cord, he measured device + cord & not device alone.
A cord is mandatory for use of the device with consumer products. So the only test that matters is one that includes that cord.



Kingpin, did you use the above supplied dc cord or did you make your own?
 

jkeny

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A cord is mandatory for use of the device with consumer products. So the only test that matters is one that includes that cord.
Sure & a speaker is mandatory for a stereo reproduction system so by your logic that is where all measurements should be taken - forget any conflating issues!


Kingpin, did you use the above supplied dc cord or did you make your own?
That's a reasonable question - any guesses as to what he used before he answers?
 

jkeny

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My guess is that he made his own cable.

There you go - so it's not, as you posted "how users utilize the unit"
 

amirm

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There you go - so it's not, as you posted "how users utilize the unit"
I said this:
Which indeed is how users utilize the unit. By measuring right at the dc terminal you are measuring a scenario that is not in use.
I am being very clear that measurements at the terminal are not representative of how the unit is used.

The measurements must include a cable unlike what you are representing. Using your speaker analogy, it is like expecting people hooking them up to an amplifier without wire. That can't happen, nor can this. So measurements need to include the interconnect and if that interconnect creates problems that this device is supposed to solve, it is a big deal.
 

jkeny

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I said this:

I am being very clear that measurements at the terminal are not representative of how the unit is used.
Characterising a device by measurement involves isolating the unit in the first place & measuring it's output alone, without any conflating variables - a basic step you continually skip.
Next step, attach cords & do far end measurements, knowing that you are now measuring device + cord/cable. IMO you have shown a continual desire to conflate these issues for whatever reasons best known to yourself.

Did you ever investigate & get to the bottom of the cause for the mains harmonics you saw in your measurements of the microrendu?

The measurements must include a cable unlike what you are representing.
You are misrepresenting what I'm saying or more worryingly, you don't understand it - it's a basic approach to measurements that everyone knows - characterise the DUT first.
As I said your approach & continually presented logic is to NOT try to characterise the device but instead conflate other variables in the measurements & claim that "this is how the device is used" or "this is what we listen to".

Why don't you just take your measurements at the speakers output because up to this point we don't hear anything - this is your argument distilled to the absurd? Your MO is - when it suits you (i.e it's a negative measurement) you show the DUT measurements - when a DUT measurement shows a positive change you state that this is immaterial as it's not what we hear & insist that only measuring the analogue side is of importance.

Using your speaker analogy, it is like expecting people hooking them up to an amplifier without wire. That can't happen, nor can this. So measurements need to include the interconnect and if that interconnect creates problems that this device is supposed to solve, it is a big deal.
I didn't see anywhere that it was claimed that the LPS-1 could be used with any cable (DIY or otherwise) & it would be deliver perfect power - did you?

Your arguments are all over the place, as usual. "So measurements need to include the interconnect" - which Kingpin didn't do - I believe he used an interconnect of his own making. But he was at least inquisitive enough to chase down the anomaly he saw in his measurements & report it here. Something I have never seen you do except when your obvious measurement gaffs are pointed out to you!

"if that interconnect creates problems that this device is supposed to solve" where is it stated that the LPS1 will solve problems that are created by a home made cord?

You need to stop plucking claims out of the air for products, building strawmen & then showing some dubious measurements to tear down your self-built strawman.
 
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microstrip

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Recently i did a measurement on the Uptone LPS-1 on ripple and noisefloor.
As Uptone stated it should completely free from 50/60Hz ripple from the AC mains.
The strange thing is that i measure a 50Hz (in my country) ripple (-90dB).
Maybe i picked up a 50Hz at my probe but to clearify i switched the LPS-1 with my LiPo powered Power Supply which is completely free from AC.
The LiPo PS was completely free from a 50Hz ripple at the output, so i can conclude that my probe wasn't pick up any interference noise.
But what could cause the 50Hz ripple at the output of the LPS-1 ?

Did anybody here some measurements on the LPS-1 ?

No, but let is look at the technical details ...

Admitting you are measuring at 5V and I am not misinterpreting the frugal information you supply the noise/ripple is around 150 microvolt - a low value. Strange it is at 50 Hz and not at 100 Hz - power supplies ripple is usually at double the mains frequency, the 50 Hz can suggest you are measuring artifacts due to the measurement technique.

As you are measuring a very low value, the conditions of carrying the measurement can affect the result. What was the load resistor? In any system using AC we can expect that ripple will depend on load. Perhaps you can try using one more resistor in series or parallel to change the load and watch the the changes - if you are really measuring ripple it should change. It is natural that ripple reduces or disappears at low load current or no current at all. Surely using a battery to power the device eliminates any ripple, but perhaps also the cause that can affect you measurement. Was your measuring computer battery powered or being used with mains supply? Any USB or network cables?

Did you check the mains voltage? Low mains can easily cause an increase in ripple.
 

Kingpin

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Mar 5, 2017
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The attached dc cable was the standard 70cm 16awg cable from Uptone.
And i must agree that the only correct presentation of the measurement is at the end of the cable, at least if you want realworld statistics.
I could make a twisted pair screened dc cable with both ends emc proof connectors to prevent any noise come in or out.

My plan is to make a decend dc cable which i always use for my power supplies.
Today i measured the same with another dc cable and gone where the 50Hz ripple, so it has to do with the dc cable.

HP3561A measured the ripple:
 

amirm

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No, but let is look at the technical details ...
Did you pay attention to which device he is measuring? This is from their web site:

"2) 100% galvanic isolation from the AC mains at all times. While one bank of ultracapacitors is supplying output, the other bank is charging. The output is never connected to the bank that is recharging, and the sophisticated design ensures silent and smooth transitioning from one bank to the other."

100% means zero connection to mains input and its AC waveform. This is a bank switching supercapacitor module. It is supposed to act like a battery, not a mains power supply as you are imagining.
 

amirm

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Apr 2, 2010
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The attached dc cable was the standard 70cm 16awg cable from Uptone.
And i must agree that the only correct presentation of the measurement is at the end of the cable, at least if you want realworld statistics.
I could make a twisted pair screened dc cable with both ends emc proof connectors to prevent any noise come in or out.

My plan is to make a decend dc cable which i always use for my power supplies.
Today i measured the same with another dc cable and gone where the 50Hz ripple, so it has to do with the dc cable.

HP3561A measured the ripple:
Good work :). If that 50 Hz bleeds into the device being powered it would show very careless design. And/or not bothering to make the simple measurement you did.
 

jkeny

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Feb 9, 2012
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The attached dc cable was the standard 70cm 16awg cable from Uptone.
So it was the Uptone cable seen in the photograph that you used. How did you attach a resistor to the end barrel plug? Got a pic of your setup?

And i must agree that the only correct presentation of the measurement is at the end of the cable, at least if you want realworld statistics.
Yes, I agree but if you had first measured the device without cable, from it's direct output, you would have answered your initial question - "is it my LPS-1 or my measurement technique that is faulty ?"
 

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