Custom Scale for Ion Gauge HELP

[Subquantum369]

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.

[billko]

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.)  😉

[JÞB · Accepted solution]

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@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.)  😉

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I Don't know why not?

[billko]

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@JÞB wrote:

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@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.)  😉

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I Don't know why not?

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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...

[Subquantum369]

Thanks for the help!

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

[billko]

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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.

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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?"  😉