Measuring O2 in enriched air

[Storker]

I'd say that paying anything to someone who claims that a 2-point calibration would require 2 knobs is a waste of money.

Interesting. Given that we seem to veer away from personal insults, I'd really like to know how you'd perform a 2-point calibration (i.e. adjusting both slope and intercept) with fewer than two adjustment dials.

 

[tarponchik]

Interesting. Given that we seem to veer away from personal insults, I'd really like to know how you'd perform a 2-point calibration (i.e. adjusting both slope and intercept) with fewer than two adjustment dials.

That's easy, my friend. You need 2 points to build a line, right? So you adjust the 2 points using 1 knob, and the built-in calculator builds the line. This is exactly how a pH-meter is calibrated with 2 or even 3 buffers.

To make it even simpler, you have only one scale, right? So why would you need 2 knobs to adust one scale?!

 

[Storker]

You need 2 points to build a line, right? So you adjust the 2 points using 1 knob

A line through two points has a slope and an intercept. To get the line right, you need have both of them right. 1 knob can only adjust one of them.

If your 1 knob adjusts the intercept, you can get one of the calibration points on the line, but not the other.
If your 1 knob adjusts the slope, you have zero on the line and can get one of the calibration points on the line, but not the other,
Your 1 knob is unable to adjust both the slope and the intercept independently.

 

[tarponchik]

A line through two points has a slope and an intercept. To get the line right, you need have both of them right. 1 knob can only adjust one of them.

If your 1 knob adjusts the intercept, you can get one of the calibration points on the line, but not the other.
If your 1 knob adjusts the slope, you have zero on the line and can get one of the calibration points on the line, but not the other,
Your 1 knob is unable to adjust both the slope and the intercept independently.

Oh boy...Yes, a linear approximation line has a slope and and intercept. However, you still do not need 2 knobs since you are adjusting the same scale. One scale => one knob! And BTW you can adjust the intercept and the slope directly only if you use zero point, like 100% N2, as one of your calibration standards.

 

[Storker]

you still do not need 2 knobs since you are adjusting the same scale

What do you mean by "scale"?

A sensor outputs a signal. That signal has some kind of proportionality to its reading. That's the slope. Which requires one knob to adjust. But then there's the offset, which may give a difference between zero concentration and zero signal. With one point to calibrate on, you can adjust the proportionality. But you don't know if the offset is right. With a two point calibration, you can check that both are good, but you need two adjustment knobs. Can't get around that, no matter how much you flail

 

[MargaritaMike]

Can you guys take this to a PM thread?

Thanks -

 

[tarponchik]

What do you mean by "scale"?

A sensor outputs a signal. That signal has some kind of proportionality to its reading. That's the slope. Which requires one knob to adjust. But then there's the offset, which may give a difference between zero concentration and zero signal. With one point to calibrate on, you can adjust the proportionality. But you don't know if the offset is right. With a two point calibration, you can check that both are good, but you need two adjustment knobs. Can't get around that, no matter how much you flail

Scale = digital display. We are talking about a XXI century digital device here but you are still thinking in analog ways. Like when you had to manually adjust Resistor 1, then turn the switch and adjust Resistor 2, etc. Forget it, these times are long over. A couple of primitive chips will do the job for you. Just imagine, once you turn the adjustment knob a-little, the device automatically switches into the calibration mode and you adjust for Standard 1. Once you'd stopped for 5 sec it automatically switches into adjusting for Standard 2. You adjust for Standard 2, stop for 5 sec, and it is ready.

 

[tursiops]

Can you guys take this to a PM thread?

Thanks -

Actually, I'm enjoying seeing Storker calmly dissassemble tarponchik. It's about time. His continuing assertion that he is the only one on the planet who knows anything about physics and math and chemistry is tiresome, as well as blatantly wrong.

 

[tarponchik]

Actually, I'm enjoying seeing Storker calmly dissassemble tarponchik. It's about time. His continuing assertion that he is the only one on the planet who knows anything about physics and math and chemistry is tiresome, as well as blatantly wrong.

Let's make this one clear once and for all. Do you agree or not that
(1) temperature has no effect on O2 sensor?
(2) pressurized gas will not cool down upon rapid expansion?

If you agree, then go read Physics for Dummies. If you do not agree, then what are you arguing here about?

 

[tursiops]

Let's make this one clear once and for all. Do you agree or not that
(1) temperature has no effect on O2 sensor?
(2) pressurized gas will not cool down upon rapid expansion?

If you agree, then go read Physics for Dummies. If you do not agree, then what are you arguing here about?

LOL! I rarely have any idea what you are arguing about, other than to be contrary.
Re (1): of course there is a temp effect, as there is a pressure effect, and a humidity effect....what do you think the relative importance of those factors is?
Re (2): basic thermodynamics, why are you even asking?