Author Topic: [Solved] Which insulation meter should I buy?  (Read 2106 times)

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Offline blueskull

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[Solved] Which insulation meter should I buy?
« on: April 08, 2017, 01:44:39 am »
In another thread I mentioned I'm building a AC/DC power supply for my laptop (see here: https://www.eevblog.com/forum/projects/a-46win3-power-adapter-with-active-pfc/).
Since I don't want myself killed, I think I should be able to test my finished product with an insulation meter.
According to UL60950-1, for world wide input voltage (I mostly live in the US, but I go to China every year to visit my family), it needs to withstand 2.5kV peak transient.
The transformer I used is designed for telecommunication system and is only certified at 1.5kV RMS isolation (2.1kV peak), therefore I need to test it myself to see if it will withstand 2.5kV.

Is there a good insulation meter that can do 2.5kv testing? So far I know Uni-T has some cheap ones, particularly UT533 and UT502A. I'm not interested in the much more expensive UT513A. My budget is $300 or less.
I don't need high accuracy -- just a qualitative test. For precision works, I have a Keysight U1461A and a Keithley 2410 SMU, but both only go to 1.1kV, even series connect them together it is still not enough to generate 2.5kV test voltage.
Any recommendations? Thanks in advance.

Bought UT502A.
« Last Edit: April 09, 2017, 12:01:00 am by blueskull »
 

Offline boggis the cat

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Re: Which insulation meter should I buy?
« Reply #1 on: April 08, 2017, 03:05:45 am »
You could ask an electrician to test it.  Cheaper than buying your own equipment.

If you want to work on the design, and possibly fix issues, then one of the cheap Chinese instruments is probably adequate.  Ideally you should verify that it is doing what it should (you will need an HV probe and suitable resistive loads), just in case it isn't quite up to specification.

An independent test house will have to certify it if you intend on selling this commercially -- the cost will make your eyes water.  For your own use it is more a case of making sure you don't risk a fire or other problem, because insurers will use that as an excuse not to pay out.
 

Offline blueskull

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Re: Which insulation meter should I buy?
« Reply #2 on: April 08, 2017, 03:19:27 am »
You could ask an electrician to test it.  Cheaper than buying your own equipment.

Well, I just want to hoard more gears. I have access to up to 15kV power supply for power semiconductor characterization, and it does everything (current limiting, voltage ramping, test output pulsing and report generating, all controlled by LabVIEW) automatically and is fully programmable.

If you want to work on the design, and possibly fix issues, then one of the cheap Chinese instruments is probably adequate.  Ideally you should verify that it is doing what it should (you will need an HV probe and suitable resistive loads), just in case it isn't quite up to specification.

I can build a resistive ladder to test its output voltage and current sourcing capability. It's rated at 1mA, 2.5kV, so I can use a 2.4MR HV resistor and a 100K resistor to scale the voltage down, then measure it with a dependable 10MR (99x higher than 100K, ignored) input DMM.

An independent test house will have to certify it if you intend on selling this commercially -- the cost will make your eyes water.  For your own use it is more a case of making sure you don't risk a fire or other problem, because insurers will use that as an excuse not to pay out.

Just build this for fun. Not exactly as a product. Though no liability (compared to selling it), I don't want to earn a Darwin Award for building and using it.
 

Offline boggis the cat

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Re: Which insulation meter should I buy?
« Reply #3 on: April 08, 2017, 05:37:13 am »
It seems to me that you should just buy whatever has the features you might want within your price range.  If you are able to characterise any critical usage then you should be fine with a cheaper, potentially less reliable, instrument.

There are also combined DMM / insulation testers, but I don't recall any rated higher than 1 kV.
 

Offline blueskull

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Re: Which insulation meter should I buy?
« Reply #4 on: April 08, 2017, 06:00:09 am »
It seems to me that you should just buy whatever has the features you might want within your price range.  If you are able to characterise any critical usage then you should be fine with a cheaper, potentially less reliable, instrument.

There are also combined DMM / insulation testers, but I don't recall any rated higher than 1 kV.

Uni-T 533 can do 2.5kV testing while still having DMM functionality. I guess I will get that one, it's only $40 higher than the 502A, so for the buck, having a backup DMM is actually not bad.
 

Offline boggis the cat

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Re: Which insulation meter should I buy?
« Reply #5 on: April 08, 2017, 11:45:05 am »
Uni-T 533 can do 2.5kV testing while still having DMM functionality. I guess I will get that one, it's only $40 higher than the 502A, so for the buck, having a backup DMM is actually not bad.
I think that only gets to 1 kV.  That is what is marked on the case.
 

Offline blueskull

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Re: Which insulation meter should I buy?
« Reply #6 on: April 09, 2017, 12:00:27 am »
Uni-T 533 can do 2.5kV testing while still having DMM functionality. I guess I will get that one, it's only $40 higher than the 502A, so for the buck, having a backup DMM is actually not bad.
I think that only gets to 1 kV.  That is what is marked on the case.

You're right. UT502A purchased.
 

Offline aargee

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Re: [Solved] Which insulation meter should I buy?
« Reply #7 on: April 10, 2017, 06:40:14 am »
Motors, etc might be OK for 1kV testing but anything we test has sensitive electronics, we only test to 500V for leakage and that's medical.
Not easy, not hard, just need to be incentivised.
 

Offline blueskull

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Re: [Solved] Which insulation meter should I buy?
« Reply #8 on: April 10, 2017, 06:47:26 am »
Motors, etc might be OK for 1kV testing but anything we test has sensitive electronics, we only test to 500V for leakage and that's medical.

You are using a certified part, I'm not. Hence I need to test it at UL voltage. I don't want to earn a Darwin's Award.
I am aware of that after hipot test at higher voltage the part may develop more leakage, therefore the DUT will be scraped, will not be used in final prototype.
 

Offline flash2b

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Re: [Solved] Which insulation meter should I buy?
« Reply #9 on: April 10, 2017, 07:09:30 pm »
I have a Duoyi DY30-2, see: http://www.dyinstrument.com/duoyi/?q=insulation_resistance_tester/DY30-1/DY30-2

Very similar specs as your UNI-T UT502A.
 


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