Moisture Analyzer

It depends upon which way round the signal range goes. -30 is 70/120ths of the way along a rising range and 50/120ths of the way along a falling range. Which, in turn is 100/150ths of 20mA rising or 100/150ths of 20mA falling, coincidentally.

All clear now?

Does that allow for the 4mA offset (assuming it's a 4-20mA loop)?

Edit: if 50% is 12mA then it is 4-20mA.

Do check the arithmetic in #1 on the grounds of suspect onset senility.

What's the question again?

As PW says, it depends whether the output is 20mA at -100degC or +20degC.

1. 20mA at +20degC

mA = 0.13333 x T + 17.3333, giving 13.3333 mA at -30degC

2. 20mA at -100degC

mA = 6.66667 - 0.13333 x T, giving 10.6667 mA at -30degC

(according to the back of my envelope).

But, I still don't understand what that's got to do with moisture analysis

Sounds like they are looking at dew points for combustion analysis. We did this sort of thing all the time on exhaust gas from continuous flow tube furnaces for heat treating small metal parts.

......I wish I had an envelope like that.....

LRV is -100 @ 4ma and URV is +20 @ 20ma.

I want to know the calculation IF my output display is -30DegC what is the value in MA and in %

0% -100 4ma

25% -70 8ma

50% -40 12ma

? -30 ?

75% -10 16ma

100% +20 20ma

Is there any graph paper there?

Very simple algebra will give you the answer. Really, you should be able to get this with a 6th grade (or less) education.

Tell you what - try and come up with the answer on your own and post it here. Then we will tell you if it is right or not.

See John DG's answer 1 at #5 above

Can you see a trend in here?

0% -100 4ma

25% -70 8ma

50% -40 12ma

? -30 ?

75% -10 16ma

100% +20 20ma

It looks like 4mA per 30 degrees to me, so 10 degrees will be 1 and a third mA.

similarly 25% is 30 degrees so 10 degrees is 8 and a third %

So your missing line is

58.333% -30 13.333 mA

simples

Read analyzer manuals, see tranducer set-up. As far as I know, if I have to design the whole set-up for this instrument (moisture analyzer), I need 2 temperature sensor (dry & wet), given those inputs, I could use some function features(means Td,Tw, is to %Moisture) through a microprocessor to arrive a plot of moisture content.

It's like %M = f(Td,Tw)

Although, perhaps there are other ways than this.

<...anyone..> has helped. Some feedback over whether the help was sufficient to determine the correct answer is now overdue.

The answer is 42.

....don't muck about Lyn.....is that % or mA....?

The answer is yes. and I am unanimous in that.

Yes I guess it is.....but you don't know Lyn.....

We'll have to wait and see.....

We don't have the answer yet.

Deep Thought is still calculating the Answer to The Ultimate Question of Life, the Universe, and Everything.

This may take awhile. There's still seven and a half million years of calculation to do.

Per the Guide, the question came as random drawings of scrabble tiles from a bag. Final answer: The computer broke.

Would you like tomato ketchup with that?

<... help me calculate this.... kindly show me the calculation...> Already done. See #1 and #8 above.

Yes, for $30.

You can do that if your process variables are linear.

Thanks John and Randall.

I don't want to worry you, but it sounds as though you are using a P205 sensor. My experience with those sensors is that they are fundamentally unstable and require lots of calibration and re-activation because the sensors are not stable. I suggest you look into a chilled mirror moisture analyzer. They are more accurate, but only go down to about -80 degrees C (with a 3 stage cooler).