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  1. #1
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    May 2007
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    Inet2000,How to programm Resistive Sensor

    I have one Water Level Sensor which has Resistance range 0-250 ohms,I want to use 50-150 ohms range(area).Any hint how to programm this sensor for Inet PCU Model 7718.

  2. #2
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    Mar 2005
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    Inet has lookup tables that you can use. They have some default values available and then you can also customize it for your specific sensor if there default values do not work for you. I assume you have or you customer has full access with the software? I don't do much with INET anymore, but there are others on here that may provide you more with more information.
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  3. #3
    Join Date
    Dec 2006
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    You will need to calculate a conversion coefficient for the Analog Input. There is a built in calculator in I/NET called a pop up calculator. It will execute all the algebra. You will need to manually enter the Counts Low, Counts High and Engineering Units Low and Engineering Units High.

    Go; Edit > Controller > Station > Parameters > Conversion Coefficients.
    On the left side is the "M" (slope) value and the right column is the "B" (offset) value. These values are used in digital-to-analog and analog-to-digital conversion..

    The 7718 PCU has 12 bit resolution.

    Do you know the correct termination on the 7718 and do you have the correct termination resistor?

    Are you familiar with lookup tables and conversion coefficients?

  4. #4
    Join Date
    May 2007
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    Thread Starter

    TP

    Quote Originally Posted by twisted pair View Post
    You will need to calculate a conversion coefficient for the Analog Input. There is a built in calculator in I/NET called a pop up calculator. It will execute all the algebra. You will need to manually enter the Counts Low, Counts High and Engineering Units Low and Engineering Units High.

    Go; Edit > Controller > Station > Parameters > Conversion Coefficients.
    On the left side is the "M" (slope) value and the right column is the "B" (offset) value. These values are used in digital-to-analog and analog-to-digital conversion..

    The 7718 PCU has 12 bit resolution.

    Do you know the correct termination on the 7718 and do you have the correct termination resistor?

    Are you familiar with lookup tables and conversion coefficients?
    I understand conversion coefficients.Let me understand Slope and Offset thoughrouly and then I will tell you if I am able to do it.About Lookup Tables if sensor is non linear it is ok,but if sensor is linear then why it is necassry to use lookup tables.

  5. #5
    Join Date
    Dec 2006
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    coldrig,

    Yes you are correct. As far as the LUT, it was a general question as well as wiring terminations and termination resistors.

    For your conversion coefficients you can look in TCON237 the I/NET 2000 Technical Reference Guide Chapter 6 Input/Output Points, which should be loaded on your PC.

  6. #6
    Join Date
    May 2007
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    330
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    Thread Starter

    TP

    Quote Originally Posted by twisted pair View Post
    coldrig,

    Yes you are correct. As far as the LUT, it was a general question as well as wiring terminations and termination resistors.

    For your conversion coefficients you can look in TCON237 the I/NET 2000 Technical Reference Guide Chapter 6 Input/Output Points, which should be loaded on your PC.
    I have successfully programmed the sensor,I calculate slope and Bias values but It was showing very small Displacement then I tried by Trial and Error method and I got 20 Numbers Displacement for Level Sensor,Now I can assign Low and high Level Numbers in between 20 Displacement Numbers.I want to ask you two questions,Does it make any harm as I am using Bias value -550.and second When float Sensor is Moving Up value is Decreasing and when moving Down it is increasing,can I reverse this to get logical value as moving up Number value should increase and when moving down it should Decrease.

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