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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Re:Predictive failures
Date: Mon, 15 Apr 2024 23:33:34 -0400
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"Don Y" <blockedofcourse@foo.invalid> wrote in message 
news:uvkn71$ngqi$2@dont-email.me...
> On 4/15/2024 10:32 AM, Martin Rid wrote:
>> Don Y <blockedofcourse@foo.invalid> Wrote in message:r
>>> Is there a general rule of thumb for signalling the likelihood ofan 
>>> "imminent" (for some value of "imminent") hardware failure?I suspect 
>>> most would involve *relative* changes that would besuggestive of 
>>> changing conditions in the components (and notdirectly related to 
>>> environmental influences).So, perhaps, a good strategy is to just 
>>> "watch" everything andnotice the sorts of changes you "typically" 
>>> encounter in the hopethat something of greater magnitude would be a 
>>> harbinger...
>>
>> Current and voltages outside of normal operation?
>
> I think "outside" is (often) likely indicative of
> "something is (already) broken".
>
> But, perhaps TRENDS in either/both can be predictive.
>
> E.g., if a (sub)circuit has always been consuming X (which
> is nominal for the design) and, over time, starts to consume
> 1.1X, is that suggestive that something is in the process of
> failing?

That depends on many other unknown factors.
Temperature sensors are common in electronics.
So is current sensing. Voltage sensing too.

>
> Note that the goal is not to troubleshoot the particular design
> or its components but, rather, act as an early warning that
> maintenance may be required (or, that performance may not be
> what you are expecting/have become accustomed to).

If the system is electronic then you can detect whether currents and/or 
votages are within expected ranges.
If they are a just a little out of expected range then you might turn on a 
warning LED.
If they are way out of range then you might tell the power supply to turn 
off quick.
By all means tell the software what has happened, but don't put software 
between the current sensor and the emergency turn off.
Be aware that components in monitoring circuits can fail too.

>
> You can include mechanisms to verify outputs are what you
> *intended* them to be (in case the output drivers have shit
> the bed).
>
> You can, also, do sanity checks that ensure values are never
> what they SHOULDN'T be (this is commonly done within software
> products -- if something "can't happen" then noticing that
> it IS happening is a sure-fire indication that something
> is broken!)
>
> [Limit switches on mechanisms are there to ensure the impossible
> is not possible -- like driving a mechanism beyond its extents]
>
> And, where possible, notice second-hand effects of your actions
> (e.g., if you switched on a load, you should see an increase
> in supplied current).
>
> But, again, these are more helpful in detecting FAILED items.

What system would you like to have early warnings for?
Are the warnings needed to indicate operation out of expected limits or to 
indicate that maintenance is required, or both?
Without detailed knowledge of the specific sytem, only speculative answers 
can be given.

>
>