On Sat, 02 Jun 2018 22:55:35 +0100, Steve Walker wrote:

On 02/06/2018 01:57, Sam wrote:


"Jimmy Wilkinson Knife" wrote in message
news
On Fri, 01 Jun 2018 17:18:32 +0100, Jimmy Wilkinson Knife
wrote:

On Fri, 01 Jun 2018 17:03:54 +0100, Dave Plowman (News)
wrote:

In article ,
Jimmy Wilkinson Knife wrote:
If you're using a sensor with electronics to set the temperature as
many do rather than a mechanical thermostat these day, the
hysteresis
is what you decide it to be.

The user doesn't always get access to that setting.

Just as well with the likes of you.

Clearly the manufacturer would limit it to a sensible range, so the
user couldn't set "200C +/- 1 billion".

Actually, shouldn't as fine a hysteresis as possible be used?

Not with something like a fridge or freezer where its better
to have the compressor start and stop less frequently.

Take it to the extreme and say the stat could measure 0.001C. Why not
do that? What you'd end up with is the equivalent of a dimmer switch on
the heating element, and once it reached temperature it would be on say
a 30% duty cycle. I'm assuming an electronic stat here and not a
bimetallic strip (do they still use those?) as you'd wear it out damn
quick. Not that a bimetallic strip could have an adjustable
hysteresis.

My marine fish-tank used to have the heaters driven by a pulse-width
modulated supply - total overkill for simple heating of a large thermal
mass by pretty low powered heaters, but I had a spare industrial PID
controller and it gave me an integrated temperature display for free.

Fish are pretty fussy, they probably liked it.

--
The skeleton found in the car park has been confirmed to be that of Richard III, but one question remains unanswered:
Who did I pay £20,000 on Ebay for?