+ Post New Thread
Results 1 to 10 of 10
  1. #1
    Member level 2
    Points: 869, Level: 6

    Join Date
    Nov 2016
    Posts
    52
    Helped
    0 / 0
    Points
    869
    Level
    6

    Interface Temperature Sensor

    Hi,
    I am having an air conditioner temperature sensor for ambient temperature measurement, which value is not in linearity. How to make out the temperature by using only the ADC Value to get degrees in the C code like any formulas.
    For a example this is my temperature sensor chart:

    Code:
    Celsius Ohms(K)  Voltage   ADC value
    15	7.447	2.968	151.349725
    16	7.148	2.918	148.8211329
    17	6.863	2.868	146.2916277
    18	6.591	2.819	143.762488
    19	6.332	2.769	141.2354022
    20	6.084	2.720	138.7136521
    21	5.847	2.671	136.1970731
    22	5.621	2.621	133.6903596
    23	5.404	2.572	131.1935588
    24	5.198	2.524	128.7084369
    25	5.000	2.475	126.2376238
    26	4.811	2.427	123.7795133
    27	4.630	2.379	121.34396
    28	4.457	2.332	118.9245804
    29	4.292	2.285	116.5251927
    30	4.133	2.238	114.1480651
    31	3.981	2.192	111.7936309
    Help me to solve this problem......

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 24,977, Level: 38
    barry's Avatar
    Join Date
    Mar 2005
    Location
    California, USA
    Posts
    4,786
    Helped
    1059 / 1059
    Points
    24,977
    Level
    38

    Re: Interface Temperature Sensor

    You need to know your sensor's voltage(resistance)/temperature relationship. You don't tell us if it's a thermistor, RTD, thermocouple, diode or what. The manufacturer should provide that information.



  3. #3
    Member level 2
    Points: 869, Level: 6

    Join Date
    Nov 2016
    Posts
    52
    Helped
    0 / 0
    Points
    869
    Level
    6

    Re: Interface Temperature Sensor

    I can’t find any datasheet or part number for my temperature sensor. All the air conditioner having a sample type of sensors.
    Click this below link for the image
    https://encrypted-tbn0.gstatic.com/i...PCpTWZ1fxDH2m0



    •   AltAdvertisement

        
       

  4. #4
    Super Moderator
    Points: 30,255, Level: 42
    andre_teprom's Avatar
    Join Date
    Nov 2006
    Location
    Brazil
    Posts
    9,052
    Helped
    1142 / 1142
    Points
    30,255
    Level
    42
    Blog Entries
    9

    Re: Interface Temperature Sensor

    Quote Originally Posted by nis2311 View Post
    How to make out the temperature by using only the ADC Value to get degrees in the C code like any formulas
    There are numerous regression calculator websites on the web on which you can insert the above input/output table, obviously selecting just one pair of parameter ( e.g : Celsius / ADC value ). These tools give you the formula that estimates with a reasonable accuracy the output value depending on the function chosen for this, usually polynomial of order 2 or 3. You can try this one, seems promising: https://planetcalc.com/5992/
    --------------------------------------------------------------------------------------------------
    Part of the world that you live in, You are the part that you're giving ( Renaissance )



    •   AltAdvertisement

        
       

  5. #5
    Super Moderator
    Points: 81,845, Level: 69
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    16,613
    Helped
    3761 / 3761
    Points
    81,845
    Level
    69

    Re: Interface Temperature Sensor

    Hi,

    There are numerous regression calculator
    Even EXCEL can do.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  6. #6
    Advanced Member level 5
    Points: 9,264, Level: 23
    Achievements:
    7 years registered
    Easyrider83's Avatar
    Join Date
    Oct 2011
    Location
    Tallinn, Estonia
    Posts
    1,603
    Helped
    368 / 368
    Points
    9,264
    Level
    23

    Re: Interface Temperature Sensor

    I recomend to use curve expert sw. Very easy to use.
    Love me or hate me. All infractions will be ignored.



  7. #7
    Member level 2
    Points: 869, Level: 6

    Join Date
    Nov 2016
    Posts
    52
    Helped
    0 / 0
    Points
    869
    Level
    6

    Re: Interface Temperature Sensor

    Thanks for your reply.....
    This site help me to solved the problem "https://planetcalc.com/5992/"



  8. #8
    Super Moderator
    Points: 265,300, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    46,354
    Helped
    14107 / 14107
    Points
    265,300
    Level
    100

    Re: Interface Temperature Sensor

    The resistance curve seems to show a 5k NTC. To calculate the translation to voltage and ADC value, you need to know the circuit, apparently a voltage divider. The transfer function can be calculated using the formulas given in NTC application literature.

    For the apparently very small temperature interval, it can be easily fitted by polynomial, as discussed above.



  9. #9
    Advanced Member level 4
    Points: 8,328, Level: 21
    Achievements:
    7 years registered
    paulfjujo's Avatar
    Join Date
    Jun 2008
    Location
    France 01120
    Posts
    1,329
    Helped
    270 / 270
    Points
    8,328
    Level
    21

    Re: Interface Temperature Sensor

    Realy ? not linear ?
    what is the problem ?

    on a very short range of temperature , even a CTN could be considered as linear

    Quote Originally Posted by nis2311 View Post
    ...which value is not in linearity.
    Click image for larger version. 

Name:	CTN.jpg 
Views:	4 
Size:	131.6 KB 
ID:	158415



    •   AltAdvertisement

        
       

  10. #10
    Super Moderator
    Points: 30,255, Level: 42
    andre_teprom's Avatar
    Join Date
    Nov 2006
    Location
    Brazil
    Posts
    9,052
    Helped
    1142 / 1142
    Points
    30,255
    Level
    42
    Blog Entries
    9

    Re: Interface Temperature Sensor

    Strictly speaking, every natural phenomenon is non-linear in some extent, and unless a detailed inspection is made - such as the one you did - it is not possible to know beforehand whether it is feasible to optimize it for the specific case of the 1-order polynomial (linear). In the above range, by visual inspection it is clearly the case. BTW, depending on the region that the PTC is biased, it may exhibit greater non-linearity
    --------------------------------------------------------------------------------------------------
    Part of the world that you live in, You are the part that you're giving ( Renaissance )



--[[ ]]--