Datalogger Temperature Sensor

david miles

Member
I would like to use my AXE110 Datalogger to record temperatures. I have tried the DS18B20 digital temp sensor that is supplied with the datalogger, but it seems to give readings in 1 degree C units. I would like a more sensitive response, something like plus or minus point one degree C, or better if possible. I am not interested in the actual temperature, only the rate of change of temperature. Any ideas anyone?

Technical

Technical Support
Staff member

It's a bit more complicated to use but gives a much higher resolution using the same sensor.

david miles

Member
datalogger temperature

I am using the programme wizard. Should I change "readtemp 7" to "readtemp 12"

David Miles

micky01

New Member

I am using the programme wizard. Should I change "readtemp 7" to "readtemp 12"

David Miles
readtemp12 is a command (check out the 2nd picaxe manual if your stuck), you still need to specify what pin the temp sensor is on, so in your case you would have:

etc etc

BeanieBots

Moderator
In case you were wondering, readtemp12 gives the temperature in 1/16ths of a C and returns bigger numbers so you should be using a word variable.
w0=w0*10/16 will give the temp in C X 10.
b2=w0/10 get degrees
b3=w0//10 get tenths

craigcurtin

Senior Member
What do you want to do with the data david ?

I found the easiest way for my application was to leave it as word data and then store it to EEPROM like that. When i send it to the PC for analysis i do all the maths in excel.

On the picaxe if i want to do comparisons for temp set points i just use the word number

'pseudo code
' READTEMP12 returns numbers that are HEX and need to be divided by 16 for Celsius
' 344 = 21.5 C
If BarTemp > 344 then Goto Overheat

Obviously you will need to convert if you are going to output to a LCD etc

regards

Craig

xnederlandx

Member
In case you were wondering, readtemp12 gives the temperature in 1/16ths of a C and returns bigger numbers so you should be using a word variable.
w0=w0*10/16 will give the temp in C X 10.
b2=w0/10 get degrees
b3=w0//10 get tenths

Thanks very much for the code!

I am making a inside/outside temp feature for my picaxe organiser and was puzzled how to convert the temprature

SCaruthers

New Member
If one wanted to use such a datalogger in a freezing (or below freezing) environment, what type battery would be best? For example, I have had problems with "button" batteries not working in very cold weather.

Cruiser

Member
Lithium (Li/FeS2) AA and AAA batteries will work below 0Â°C (but not sure how far below) as they don't contain water in their electrolyte.

Super long shelf life (15 years).

Do a bit of research on Energizer L91 (AA) and L92 (AAA) batteries.

They cost 3 times the price of Alkalines though.

Cruiser.

Dippy

Moderator
I agree with Cruiser.

There's a bit of info at the bottom of Page 1 of this DATA SHEET about lithium vs alkaline.
http://data.energizer.com/PDFs/l91.pdf

Panasonic make a CRV3 lithium note 3V in AA format.
http://www.farnell.com/datasheets/38704.pdf
Bottom of page 1 shows lithium vs Alkaline at different temps.

A number of manufs do Lithium Thionyl Chloride (usually 3.0 / 3.6V) which I have used in devices used in the 'wilderness' for several years, eg:
http://www.farnell.com/datasheets/75434.pdf
and
http://www.farnell.com/datasheets/85380.pdf
the SAFT ones (previously Crompton Eternacell taken over by Saft) I found to be excellent.

Also Sonnenschein is another well known (by many) manuf.
If you want to run a PP3 plus regulator look at Ultralife and there is a similar one from someone else but I've forgotten.

BE AWARE:
Watch out for voltage even in AA/C/D size format.