On 13/04/2018 16:44, whisky-dave wrote:
On Friday, 13 April 2018 15:44:58 UTC+1, The Natural Philosopher wrote:

Thanks, yes I agree completely about the sampling strategy, but I'd sort
out details once I knew the capability of the device. My point was that
I think I am looking for slowish variations rather than microsecond
transients. (I am trying to find what is killing electric kettle elements).

My point is, do the low pass filtering in software, though.

A bridge rectifier and smoothing cap is a peak voltage reading abortion
for this: you want to do an RMS average especially for kettle elements.

My solution is less components, but more code.

Code is cheap!

Depending on how long it takes you.
The idea device would just be a pen holder that respondened to changes in the voltage a bit like an old chart recorder and I'm still not sure how you'll detect what's blowing a kettle elimante I wouldn't have thought they'd be suseptable to transients.


Only issue is doing a square root in binary integers...arduinos don't
have native floating point ****!

I'm still note sure how you'll know what caused teh transcient even after detecting it.

How long will this kettle element be ON for ?




OK, it's not an element in a kettle. It's in a wallpaper stripper, used
as a steam generator. They are typically failing after half a dozen
(separate) 20 minute sessions. They are not being boiled dry, they are
on a timer to prevent that. Oh, and nothing else seems to be blowing. I
*originally* thought it must be a problem with the chemistry of the
local water supply but two separate chemists with long experience are
convinced that this is unlikely.

I just thought that for less than £100 worth of re-useable bits it would
be nice to investigate the electrics.