Rate of change Measurement

Attila Kovacs

Hi Everybody,

I am a newbee here having a project idea with some difficulties:


I want to build a Rate of Change Meter on Temperature.

Input signal: analogue (from a thermocouple or LM34)
Sampling time: adjustable constant
Integration time: adjustable constant for elimination of noises
Required output: rate of change
Transmission: rate of change on serial RF line

Does anybody has such project or can help me some codes?
Any help is very welcomed

thank you very much
regards,
redrunner

SRLM

So, you basically want to build something that measures the second derivative of temperature? Out of curiosity: why would you be interested in that number?

In any case, I'd probably start by looking at the various papers and books on numerical differentiation, such as this: http://books.google.com/books?id=lxGPQmuSwBQC&pg=PA214&lpg=PA214&dq=discrete+numerical+derivative&source=bl&ots=Jnn9OjfehR&sig=xpogU8Ifs3FT1raf3Gh_ZHSNZ_E&hl=en&sa=X&ei=dHP_UP69NYmEjAKt2YDgDA&ved=0CDwQ6AEwAg#v=onepage&q&f=false

Other than that, it's basically adding the building blocks together: code to read the sensor, code to transmit the result, and your differentiation code in the middle.

Phil Pilgrim (PhiPi)

SRLM wrote:

So, you basically want to build something that measures the second derivative of temperature?

Rate of change is the first derivative: i.e. how fast the temp is rising or falling. The second derivative measures the rate of change in the rate of change, IOW "temperature acceleration."

-Phil

SRLM

Phil Pilgrim (PhiPi) wrote: »

Rate of change is the first derivative: i.e. how fast the temp is rising or falling. The second derivative measures the rate of change in the rate of change, IOW "temperature acceleration."

-Phil

Interesting. I didn't know that "rate of change" was considered a single phrase. I parsed it to be "change" in temperature (it's "velocity"), and then the rate of that (it's "acceleration"). But, I found several sources that confirm that rate of change is indeed a single phrase.

Thanks for catching that.

Phil Pilgrim (PhiPi)

Think of it this way: If the temperature rises from 67F to 80F in two hours, the "change" is +13F, but the "rate of change" is +13F/2 hrs. or +6.5F/hr. IOW, the rate is dependent upon the time that elapsed during the change.

-Phil

Attila Kovacs

Hi,

Thanks for quick reply.
Rate of change of temperature gives me additional information about process to be supervised (slope of changing is a very useful extension of discreet sampling of function T(t).

I have found some lexical information about numerical differentiation at :
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDAQFjAA&url=http%3A%2F%2Fwww.parallax.com%2FPortals%2F0%2FDownloads%2Fdocs%2Fprod%2Fsic%2FWeb-PC-v1.0.pdf&ei=Bcr_UN7cDsvDswa5xoDYAQ&usg=AFQjCNHAESjK39kXgzNOLDPnQAZL2h1ZWA&sig2=qn4L9tc7ZoUntkmq5VlP7w&bvm=bv.41248874,d.Yms

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDcQFjAB&url=http%3A%2F%2Fwww.parallax.com%2FPortals%2F0%2FDownloads%2Fdocs%2Fprod%2Fsic%2FWeb-PC-v1.0.pdf&ei=Mcr_UNXNJMTfsgat5oCgBQ&usg=AFQjCNHAESjK39kXgzNOLDPnQAZL2h1ZWA&sig2=jcW1IKv-JLaq6FLQiXmqZA&bvm=bv.41248874,d.Yms

If somebody has implemented such temperature monitoring application, I would be glad to have it

thanks a lot