Pic NTC calculation

[ssaguiar]

I needed to calculate a table, for a pic project, to use a thermistor (NTC) in a resistive divider circuit.
So, I made an excell spreadsheet to make this.
The spreadsheet is attached to this post.

You must inform:
- the pic's supply voltage;
- the adc resolution (8 or 10 bits - if 10 bits, must change the formating of hex column);
- the temperatures;
- the resistance of the ntc, at the temperature;

The circuit is a resistive divider, with the first resistor with a value of 1K1 1% and the second resistor composed of the ntc in paralel with an 7K5 1% resistor.

Observation: I have made this spreadsheet using openoffice and exported it in excell format. The formula used to print the hexadecimal values was:
=DECAHEX(G22;2)
This to print the hexa of cell G22, showing it using 2 characteres.
If you use MS excell, you must change the formula.

Help this can be useful.

 

[ssaguiar]

Added a graphic and some comments to the columns headers.

 

[Acetronics]

Hi, Ssaguiar

Could you explain which kind of file this is ???

couldn't succeed to open it whether the used program ( open office, Excel, ... etc,etc ...)

Thanks

Alain

 

[ssaguiar]

Hi, Ssaguiar

Could you explain which kind of file this is ???

couldn't succeed to open it whether the used program ( open office, Excel, ... etc,etc ...)

Thanks

Alain

Hi, Alain.
I used the BRoffice 3.X wich is the OpenOffice, in Bazilian Portuguese.
I exported the file in MS Excell format, but, as I don't have it installed, I could not test it, but I can open and edit it using BROffice (OpenOffice 3.x).
Now, I attached the file thermistor.zip, wich contains the file thermistor.ods, in OpenOffice format.

Please, let me know if it works.

Sergio

 

[Acetronics]

Hi, Ssaguiar

Finally got it ...

1) unzipped your file with UltraZip ( a free dezipper )
2) unzipped the produced file with 7 zip ( another Free dezipper )
and 3) Yess , got an Open Office file ...

Alain

PS: here is a little document explaining how to achieve a good linearization ... but that need a translation.

 

[ssaguiar]

I am glad you got it.
I don't understand why you had to use 2 unzipers (UltraZip and 7zip), because I used only the winrar to compress the file in zip format.
The most important is that it worked for you.
Let me know if the spreadsheet is usefull.

Sergio

PS: I see that you like Asterix. My avatar is Asterix, in several places.
I will upload it asap.
I like it since I was a student at Marseille, in France, a loooong time ago (1971).

 

[Acetronics]

I don't understand why you had to use 2 unzipers (UltraZip and 7zip), because I used only the winrar to compress the file in zip format.
Sergio

I do not understand nor ... but it works !!!

Thanks once more
Alain

!!! changed the download

 

[toonman]

Hi ssaguiar, not bad ... quite usefull. I just changed the spreadsheet so I get 10bit and 16bit values in HEX as well. I altered the formula to =DEC2HEX(G3,(CEILING((B6/4),1))). Thank you for sharing!