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low cost thermocouple DAQ that works with ubuntu linux tia sal22

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I never said that it was. I am talking about the device I posted a link to. The devices I used to make, twenty years ago were far more accurate than that, so they have gotten even better since. That has nothing to do with this cheap cen-tech device for consumer use.

Usually not.

Not at all. All the operator need to do is make the needed compensations for his readings. Again it comes down to operator understanding.

So IF you had said it is very easy to forget about emissivity, you might be closer to being right. Instead you make a blanket claim that I do not know about emissivity, which is untrue.

That is silly. IR is instant. it travels at light speed. The thermocouple has to soak up the temperature it is sensing, and it has to settle in at that temperature. That takes time because metal does not conduct heat through itself instantaneously. The IR device gives an accurate reading within milliseconds of viewing the target.

IR and the air gap between it and what it reads has no such restriction because the air AND the bolometer do NOT need to be brought up to the test temperature.

Another KNOWN factor. However, my cheap device still tells me the wall temp of my room from 12 feet away just as well as it does from an inch away. It works fine.

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I AM THAT I AM
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On a sunny day (Sat, 04 Dec 2010 14:09:56 -0500) it happened Phil Hobbs wrote in :

it does *NOT MOVE AT ALL*.

EITHER*.

course.

Oh no.

It all depends, apart from the issues of ego and losing face, for a man it is better to admit he is wrong, simply, at times, a pussy will blow smoke and go side-paths. You show how much you know about piezo, but this was about electrostatics. Apples and oranges.

Let's look a bit closer.

If you take 'capacitor mike' literally, as one MIGHT do, then neither the capacitor mike, nor the electret mike, really uses the CAPACITANCE. One could make a 'capacitor mike' by making a tuned circuit (LC) oscillator, and have one fixed and one moving membrane form a capacitor, and the frequency would change under influence of the capacitance, so under the influence of the membrane moving, so under the influence of air pressure changes, say audible sound if it is in the air pressure changes occur in the right frequency range. There is a square in there somewhere, so it would not be all that linear over a large movement. Once could use a FM radio to detect this if the circuit was made to oscillate in the FM band. Maybe the correct word here is 'parametric'.

Then there is the real 'capacitor mike' as we call it, and that is actually an 'electrostatic mike',

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where something moves RELATIVE TO (old Einstein ;-) something else, where one of the objects carries a charge. This is the SAME in the 'capacitor mike' and the 'electret mike'.

The difference is that the capacitor mike needs an external supply for the voltage, and the electret uses a polarised film, so needs no external supply, simpler, cheaper, better, no hum, no filtering problems.

So for all practical purposes, and all theoretical purposes, we can compare a 'capacitor mike' with an 'electret mike', as both use exactly the same mechanism. Thank you for your attention and have a nice day.

PS There are also electrostatic speakers, Quad comes to mind as a manufacturer. Very much HiFi. I have even listened to electrostatic headphones. El Pante

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Jan Panteltje

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