[chbot] Insulation Tester

Richard Jones richard.jones.1952 at gmail.com
Sun Jan 24 08:49:08 GMT 2021

Here is a link to the insulation tester that I bought for $38.61US:
https://www.aliexpress.com/item/32888285436.html  The goal being not to
repeat destruction of my test setup by faulty PSU construction.

For a PSU / Wall Wart test I short live and neutral together and perform a
1000V test between Live+Neutral and Earth (if there is one) and between
Live+Neutral and 0v output.

So far I've not detected any leakage on everything that I've tested, and
I've not blown up any electronics either.

When I measured the tester output voltage it came up short of 1000V, which
I put down to the input resistance of my voltmeter in series with the
unspecified output resistance of the tester.

I could bring the tester along to the next meeting if anyone is interested,
while keeping in mind that it is a potentially dangerous device (pun
intended :-)

I'm no expert on insulation testing other than having designed Telco line
interfaces years ago, so any comments on the test approach most welcome.

For telco line interfaces we used to consider 5mm PCB gaps between copper
tracks adequate insulation. These days I find that JLCPCB are quite happy
to route air gaps between mains and low voltage connections for no extra
charge. So I design 1.5mm air gaps as well on a pcb routing layer. I view
this as a much safer approach to give reasonable isolation even when things
get damp and/or dirty.

Richard Jones

On Sun, Jan 24, 2021 at 2:24 PM Volker Kuhlmann <list57 at top.geek.nz> wrote:

> On Thu 21 Jan 2021 14:33:11 NZDT +1300, Richard Jones wrote:
> > Consequently I bought a new laptop motherboard, rpi, and a HV insulation
> > tester!
> Could you give details on the HV tester, please? How much can one test
> without blowing electronics up with the tester? Ta.
> Volker
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