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Subquantum369

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04-17-2014 09:09 AM - edited 04-17-2014 09:14 AM

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I have a Kurt J Lesker 354 ion vacuum gauge that puts out an analog 0-9v representing vacuum pressure in Torr.

I'm having trouble getting the custom scaling to work. I have been trying to use the DAQ assistant custom polynomial scale since I need logarithmic scaling.

The KJL354 manual gives the analog output (log-linear 0 to 9 Vdc,1 volt per decade)

Pressure Torr Voltage

1.0E-10 0.0

1.0E-09 1.0

1.0E-08 2.0

1.0E-07 3.0

1.0E-06 4.0

1.0E-05 5.0

1.0E-04 6.0

1.0E-03 7.0

1.0E-02 8.0

5.0E-02 8.698

As you can see, the highest vacuum at 1^(-10), is zero volts and every volt represents a magnitude of ten as the vacuum pressure decreases to 5^(-2)

since these are negative values inverse of the voltage, I put polynomial scale coefficients at:

Order Coefficient

a0 1

+x*a1 10

+x^2*a2 9

+x^3*a3 8

+x^4*a4 7

+x^5*a5 6

+x^6*a6 5

+x^7*a7 4

+x^8*a8 3

+x^9*a9 2

+x^10*a10 1

The scale ends up upside down and representing a small range of exponents, whether I put the coefficients ascending or descending.

I have the pre-scale selected as volts. from what I understand each volt would be the coefficient of x.

Any Help would be apprecieted.

Solved! Go to Solution.

billko

Proven Zealot

04-17-2014 09:36 AM

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The manual is here. Look on page 32 of the pdf and it shows the conversion formulae. (Hey, I'm not going to do ALL the legwork for you.) 😉

Bill

(Mid-Level minion.)

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Solution

Accepted by Subquantum369

JÞB

Knight of NI

04-17-2014 09:51 AM

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billko

Proven Zealot

04-17-2014 09:54 AM - edited 04-17-2014 09:58 AM

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@JÞB wrote:

@billko wrote:

The manual is here. Look on page 32 of the pdf and it shows the conversion formulae. (Hey, I'm not going to do ALL the legwork for you.) 😉

I Don't know why not?

LOL it was more an exercise about how to go about finding information. 😉

You know, all that good stuff about teaching a man to fish, etc, etc...

Bill

(Mid-Level minion.)

My support system ensures that I don't look totally incompetent.

Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

Humble author of the CLAD Nugget.

(Mid-Level minion.)

My support system ensures that I don't look totally incompetent.

Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

Humble author of the CLAD Nugget.

04-17-2014 09:59 AM

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Thanks for the help!

I thought I could do it from the custom scale in DAQ Assistant, but your solution makes more sense.

billko

Proven Zealot

04-17-2014 10:01 AM

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@Subquantum369 wrote:

Thanks for the help!

I thought I could do it from the custom scale in DAQ Assistant, but your solution makes more sense.

I don't even want to think about how many times I overcomplicated something and someone else just comes along and says, "Why not just do it this way?" 😉

Bill

(Mid-Level minion.)

My support system ensures that I don't look totally incompetent.

Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

Humble author of the CLAD Nugget.

(Mid-Level minion.)

My support system ensures that I don't look totally incompetent.

Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

Humble author of the CLAD Nugget.