Digital and Analogue in real terms what do they mean?

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
With a PLC a 256 step controller was considered analogue even if technically it was still digital, but a CD player is called digital even with far smaller steps.

So if a dial is connected to a scroll wheel as used in an old computer mouse then it is digital but if it connects to a variable resistor with a carbon track it's analogue, but a wire wound variable resistor then it changes in steps so is digital. So in real terms turning a dial you have no idea if analogue or digital, however if you select temperature with the dial position then I would call it analogue, but if it has a LCD display giving numbers it's digital but if it also has a bar graph not so defined.

So taking a very common human machine interface the wall thermostat, what is digital and what is analogue, are all off/on thermostats digital and all modulating thermostats analogue even if that modulation is in steps, or are all thermostats digital and so it's pointless to use digital or analogue when describing them?

As to the TRV some old models did switch off/on, but in the main the control is gradual, be it a wax pellet or a motor, they close bit by bit, however some have a LCD display so will show a setting at best 0.5°C increments but some do not have anything more than a single button the control being from a PC or Phone. I would say they are analogue what ever the display, and motorised valves are digital i.e. off/on.

So with heating systems analogue is far better than digital, but the general public that digital is best, so should the two words be simply banned to save confusion?

Thoughts please.
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The term digital was hijacked by marketing decades ago to mean something more modern and sophisticated than an old analog control. Each have there place but their are few true analog systems (those with an infinite resolution) around today. Many systems appear analog but are actually digital eg. modern vehicle dashboards...the needles are driven by stepper motors.

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