I dont have the details of the system such as diagrams schematics. So this will be a big picture question.

I have a system where a 4 gauge transducers are connected to an amplifier box. Amplifier box also supplies power to the transducers. Amplifier box is supplied by 12V power supply. The problem was, at the output I observe around 25mV 1Hz square wave noise on outputs. I tried with different 12V power supplies one was 1A rated I had the same issue.

So I sent the system back to the supplier and they examined the same setup didn't observe this noise.

The only difference is that we use different 12V power supply for the amplifier. And in US they use 60Hz AC mains and we use 50Hz(I don't think this has any effect though).

I just checked the manual again and it says the power supply recommended for this amplifier is 12V and 2A.

Can this be the reason for a 25mV square-wave noise. Would using lets say 12V 1A power supply cause such issue instead of a recommended 12V 2A power supply?

Since the only difference between the setups is the power supply they use I couldn't find any other reason for the source of this type of noise.

  • \$\begingroup\$ Need a crystal ball to tell. Using it outside its specifications anything can happen. Find an adequate lab PSU (2A or more) and test with that as a first step. \$\endgroup\$ Mar 21, 2017 at 10:03

1 Answer 1


The best answer I can give is "maybe".

But first there is an issue that needs to be addressed. It's like this:

If you're not following the manufacturer's instructions, and the unit is not operating properly, you need to start following the manufacturer's instructions before you start complaining.

I am astounded that you don't understand this.

So get a 2 amp power supply and try it. You should have done that before you sent the unit back to the manufacturer, and I wonder if you informed them that you were using an undersized power supply. If not, you were wasting their time.

Of course, when you say, "I tried with different 12V power supplies one was 1A rated I had the same issue," the obvious question is, what were the other supplies rated for? If the 1 amp unit was the beefiest you had, you really were wasting everybody's time.

With that said, a marginal power supply might, under some circumstances, cause something like you've seen, but it requires a pretty delicate balance of being right on the edge of being in current limit. 1 Hz is the sort of frequency that is hard to explain. It's really too slow for most electronic issues, and too fast for thermal, but it's not impossible. It ought to be easy enough to see, though. Use one of your other 12 volt supplies as a reference, isolate either your scope or your power supplies from AC ground, and look at the amplifier 12 volts. If the power supply is the culprit you'll probably see the same 1 Hz there. And, by the way, if you don't isolate properly you'll probably damage your scope.


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