Thermistors questions

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i am using a MF58 glass bead 100k ntc with pull down of 10k and a series resister of 1k with my micro controler atmega32.

Rjchoudhary

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Rajat choudhary wrote:
acually i  am unable to understand the three coefficient A,B,and c.what  are they and how to find the value of that.

https://instrumentationtools.com...

I googled "how to find RTD coefficient" to find the above

 

Jim

Are they not listed in the datasheet for the RTD?

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

Last Edited: Tue. Mar 17, 2020 - 12:33 PM
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Rajat choudhary wrote:

acually i  am unable to understand the three coefficient A,B,and c.what  are they and how to find the value of that.

 

 

THis is getting annoying....

 

As asked:

ki0bk wrote:
What temperature range are you measuring? What NTC have you chosen to use, part number?

 

Provide a link to the datasheet.

 

Rajat choudhary wrote:
acually i  am unable to understand the three coefficient A,B,and c.what  are they and how to find the value of that.

 

Provide the link to the datasheet for the part.

 

If you continue to offer up nothing you will get nothing...and another thread locked.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Rajat choudhary wrote:
i am using a MF58 glass bead 100k ntc with pull down of 10k and a series resister of 1k with my micro controler atmega32.

Here is a datasheet: https://media.digikey.com/pdf/Da...

for a type MF58, but you will need to know it's full part number as that tells you more about the particular RTD....

Now, in case you missed it in another thread, What is the temperature range you want to measure?

Why use an RTD and not a temperature chip, (analog or digital)?

What is your application?

 

Jim

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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ki0bk wrote:

Are they A,B,C Coefficients not listed in the datasheet for the RTD?

I've never seen these listed in a thermistor datasheet. I don't know why not,

 

Manufacturers instead give either a temperature-to-resistance lookup table or more generally the beta value and R25 which specifies the curve around two temperature points. If your measurement of interest is substantially outside that temperature range then accuracy will become worse.

 

Ignore the https://instrumentationtools.com... link; that is specifically about Platinum Resistance Thermometers, not thermistors.

The better link is  https://learn.adafruit.com/thermistor/using-a-thermistor

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As i said I'm new with avr so i doing small projects but the circuit i have got is only with 100k ntc so i have to make program on it

Rjchoudhary

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Rajat choudhary wrote:
As i said I'm new with avr so i doing small projects but the circuit i have got is only with 100k ntc so i have to make program on it

 

So, this is a school project then?

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Rajat choudhary wrote:
As i said I'm new with avr

As I said, the basics of how thermistors work, how to use them in a potential divider, etc has nothing to do with microcontrollers - AVR or other.

 

You need to understand those things before you can start bringing microcontrollers into the picture.

 

And, as others have said, thermistors are very long-established, widely-used, well-known devices - so there is no shortage of information, examples, etc available on the interwebs and even in good, old-fashioned books!

 

In one of your many re-posts of this, Kartman wrote:

What research have you done? The thermistor is hardly new, so you're not on the bleeding edge. If you Google arduino thermistor, you'll get a few pertinent hits. Start your research there.

 

Hint - add Arduino to just about anything you have a question about (regarding microcontrollers). Odds are you'll get something useful as anything that is of any interest to a hobbyist has probably been done with an Arduino, a blog written about it and sample code and circuit. Don't tell me you don't want to use Arduino, as this makes little difference - the Arduino is just an AVR on a circuit board - no magic.

 

https://www.avrfreaks.net/commen...

 

 

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Rajat choudhary wrote:
... the 100k ntc temperature calculation ...
fyi, a new arrival

Texas Instruments PTC Thermistors | Mouser

...

The TMP63 takes advantage of benefits over NTC thermistors such as no extra linearization circuitry, minimized calibration, and less resistance tolerance variation. It also offers larger sensitivity at high temperatures and simplified conversion methods to save time and memory in the processor.

...

edit : target

 

"Dare to be naïve." - Buckminster Fuller

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Yes sir it is my school project can you give me any example code with 100k ntc

Rjchoudhary

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You still haven't provided the information that's been requested from you - what is the part number, exactly, of the thermistor you are using?

 

Have you really not been able to find any example code anywhere at all on the internet or in your set books?

 

If it is a school project, then it is expected that you should be doing the work - yourself

If you're really stuck, you should be going to your teacher for help.

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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You still have not told us your expected temperature range you want to measure!

How will display the results? single LED's, 7segment LEDs, LCD, Serial terminal, other?

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

Last Edited: Tue. Mar 17, 2020 - 08:29 PM
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Rajat choudhary wrote:
Yes sir it is my school project can you give me any example code with 100k ntc

 

I give up.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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What do you want to do?  You must say so!!  Measuring temperature can be much different than using temperature.

 

For example, if you want to sound an alarm at a calibrated temperature setpoint, you may not need to do any type of calculation or math at all.

You can simply set a voltage trip point where some action takes place.  Dial in a pot or software until the action occurs, that is the setpoint.   In that case the software really has no idea at all what the temperature is or that temperature is even involved; it just knows at  xx volts to sound the alarm.

 

Sometimes people go through all kinds of hocus pokus, calculations, linearizations, etc and completely waste all that complexity just to trip at some setpoint.

b=a

calculate sin(a)-sin(b):

1) calc  sin(a) using 5th order polynomial expansion 

2) calc  sin(b) using 5th order polynomial expansion 

3) form difference.

 

shortcut: 0

  

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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You can lead a horse to a useful internet page but you can't make him read it.

 

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N.Winterbottom wrote:

You can lead a horse to a useful internet page but you can't make him read it.

 

+1

 

I would suggest we stop feeding this one until it spits up a little

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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What do you want your project to DO?   Is there an application in mind, or just experimentation?

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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