I was hoping to compare PSUs.
I found you can measure ripple with a DMM.
But when I read up on it, some say you can, some say you can't some say it depends, some say it is more complicated than that.
But i don't understand the reasons.
I have an Aneng AN870:
https://www.aliexpress.com/item/33004463675.html?spm=a2g0o.order_list.0.0.b1c11802kFg5wk
First thing is to find whether mine is able to.
it states True RMS.
I found you can measure ripple with a DMM.
But when I read up on it, some say you can, some say you can't some say it depends, some say it is more complicated than that.
But i don't understand the reasons.
I have an Aneng AN870:
https://www.aliexpress.com/item/33004463675.html?spm=a2g0o.order_list.0.0.b1c11802kFg5wk
First thing is to find whether mine is able to.
it states True RMS.
Then it probably can.
Some really cheap meters cannot measure AC on top of DC. Here is the very simple test. Take a 9v battery and measure its DC voltage. You should get something near 9vDC. Now switch your meter to AC volts and remeasure. A good meter will initially measure something, but will settle down to zero volts AC after a moment. However, if your meter tells you there is something like 12vAC on that 9v battery, then that meter cannot handle it.
I use my Fluke meters to measure ripple on top of DC all the time
Some really cheap meters cannot measure AC on top of DC. Here is the very simple test. Take a 9v battery and measure its DC voltage. You should get something near 9vDC. Now switch your meter to AC volts and remeasure. A good meter will initially measure something, but will settle down to zero volts AC after a moment. However, if your meter tells you there is something like 12vAC on that 9v battery, then that meter cannot handle it.
I use my Fluke meters to measure ripple on top of DC all the time
Wonderful.
Thank you.
Good news. It does exactly that.
Well, flips to OL first, then briefly shows a low voltage and yes, drops to zero.
Is it just as simple as using the AC reading on the output of the power supply?
I am not too worried about its accuracy, mainly to compare one supply to another.
It seems to be showing 6mV on an old Linear supply and 5mV on my L-Ad.
Are those the sort of range of numbers I would expect?
Am I reading it right?
Thank you.
Good news. It does exactly that.
Well, flips to OL first, then briefly shows a low voltage and yes, drops to zero.
Is it just as simple as using the AC reading on the output of the power supply?
I am not too worried about its accuracy, mainly to compare one supply to another.
It seems to be showing 6mV on an old Linear supply and 5mV on my L-Ad.
Are those the sort of range of numbers I would expect?
Am I reading it right?
It would be a very bad DMM when it would measure 12 V AC on a 9V (DC) battery 🙂
No idea what an L-ad is as it is jargon probably but 6 mV ripple/noise could be right when the power supply does not have a load. It is not a very precise measurement for the average DMM but with either 50 or 60 Hz mains voltage it will be about right and it gives an indication. There are other instruments more capable of precise measuring of noise and ripple voltages.
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oops. Sorry. L-Ad is a Salas L-Adapter.
The measurements were with load.
Thank you for that confirmation and information.
So I can just get a ball park idea is good fun.
Compare one supply to another.
I would like an oscilloscope to be able to read it properly but I am still a way off that.
This is fun enough for now.
The measurements were with load.
Thank you for that confirmation and information.
So I can just get a ball park idea is good fun.
Compare one supply to another.
I would like an oscilloscope to be able to read it properly but I am still a way off that.
This is fun enough for now.
If I want to determine a DC source ripple with my Fluke meters, I simply put it on AC volts and read the amount.
I'm usually satisfied when the reading is 0.001-.0.000v AC.
So what sort of number range is considered good/acceptable/bad from a Linear Power Supply.
Obviously 0.000V is acceptable. 😊
Am I meant to take readings with or without load?
I am taking it with load thinking that is when I care about it.
(Although I have no way of knowing how near my dmm is to reality)
Obviously 0.000V is acceptable. 😊
Am I meant to take readings with or without load?
I am taking it with load thinking that is when I care about it.
(Although I have no way of knowing how near my dmm is to reality)
It depends.
Before/after loads it will naturally be different.
And depends on is theres a regulater involved.
The lower, naturally is better.
Before/after loads it will naturally be different.
And depends on is theres a regulater involved.
The lower, naturally is better.
A 12V sealed lead battery that is not being charged (i.e. it is not connected) should have very little ripple voltage 🙂 Normally ripple voltage is a subject before and even after regulators in AC/DC conversion power supplies. A 12V lead acid battery that is being charged has ripple voltage generated by its charger. It is one of the parameters that have influence on battery lifetime.
Grarea: bringing down ripple voltage is a good thing to do in power supplies. CRC or CLC filtering before the regulator brings more than one would assume. It also filters out incoming HF/RF.
Grarea: bringing down ripple voltage is a good thing to do in power supplies. CRC or CLC filtering before the regulator brings more than one would assume. It also filters out incoming HF/RF.
AC mV mode can be of different noise sensitivity between various meters and test setups. A fast verification is, while measuring, don't disturb the test leads and power down the device under test. Compare the on/off readings. If the DMM shows more than zero when the DUT is off, keep this value in mind as the particular test situation's noise floor limit.
Depending on the meter it may help, none of my current meters need the blocking capacitor at low voltages but I have had meters in the past that had problems particularly on HV DC supplies with very low ripple and the capacitor made ripple/noise measurements possible with a meter. I generally use a scope for these measurements particularly with SMPS.
Indeed, I agree.
A scope is really the best (and visual) way of determining such things.
My Heath VTVM was never confused. It had a blocking cap.
But it seems none of us know what Aneng's meter does with AC on DC. He would not be asking if he knew, or if he had a 'scope. The blocking cap is a direct hack at the unknowns.