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Mettler TM15 RDT PT100 mecanical temperature display 1970 test teardown

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oz2cpu:
this one i just have to share :-)

my latest
Mettler TM15 RDT PT100 temperature display 1970 test teardown

This is one of them WOW how cool type of display readout tech :-)
mecanical counter, gears, stepper motor, feedback potentiometers,
bridge, PT100 sensor, AC drive and compare with ref potentiometer,
to figure out if motor needs to go forward or reverse, amazingly nice construction, and it really works.

video link
https://youtu.be/DJZji0WJ-Ho

MK14:
Nice video, and very interesting piece of equipment.

I'm wondering, what the display shows if the temperature goes negative?
Also, as it seems to show ' [ o ] C', can it be switched to a Fahrenheit scale 'F'?

Edit: Putting some table salt, onto the ice (ideally with little or no, extra water, as it dilutes the salt action), should create temperatures below zero Centigrade.

TomKatt:
Great video!  Subscribed!

They had several numeric display technologies in 1970 (planar, nixie, numitron etc)...  I wonder why they went with a mechanical display ?

MK14:

--- Quote from: TomKatt on November 02, 2023, 12:19:07 pm ---Great video!  Subscribed!

They had several numeric display technologies in 1970 (planar, nixie, numitron etc)...  I wonder why they went with a mechanical display ?

--- End quote ---

I think it is because its circuit action, is basically analogue (comparison, between the measured temperature, and the potentiometer, which moves along with the mechanical counters, if I have following things correctly), so it doesn't need the digital circuitry for the other display types, which would have been very expensive, at that time (or even non-existent, depending on when this design was first used).
I.e. If this technology was old enough (when it first came out), it could pre-date, integrated circuit counters and stuff.

oz2cpu:
>I wonder why they went with a mechanical display ?

I think it is due to the compare potentiometer is insanely accurate and linear,
converting potentiometer position to a type of readout that is non mechanic
would add all sorts of not so accurate details

I also like the fact that this unit display the last known value, when power is missing

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