pt100/pt1000 as temp sensor

[naz83]

Hi.
I am thinking of using pt100/pt1000 as temperature sensors in designing an anemometer. the two sensors must be heated equally and one shieled from the other, air blown over one should affect the bridge balance and give a voltage output related to the speed of air..... i then need to use an ADC and AVR to display the results.

can any1 suggest any circuit arrangement for the above and any suggestions plz...........

 

[keith1200rs]

A few ideas here maybe:





**broken link removed**

Keith.

 

[naz83]

hi,

i have tried the thermistor circuit it dint work well.. as one thermistor was heated and another was at room temp... so i was thinking of heating both the sensors and subjecting only 1 to air flow.. i was thinking about using 2 1k thermistors in a wheatstone's bridge with 1k resistors and then amplifying using an opamp....
i am confused as to use constant current or constant voltage and which one will work best for my application?

any circuits/ideas plz help...............

 

[keith1200rs]

I am afraid I don't know which is better - constant current or constant voltage. Both will be non-linear and need calibration, I would expect. I did do something similar nearly 30 years ago but I have no documentation for it. I seem to think I used constant voltage.

Keith

 

[naz83]

I did experiment with pt1000 today.

I did use two bridges each having one pt1000 as a sensor and one of the resistors was 1.2k. as a result the pt1000 was heated to reach 1.2k.

Its like having two anemometers, one of them was subjected to air flow and the other was like a reference. and the outputs from these two was given to a differential amplifier to amplify the difference between the two. I did get it working, when no air flows the diff output is 0.13v and on air flow depending on the amount of airflow it increased to 3.0v.

could u suggest what needs to be done further to get it to a uc and the AVR part plz....

 

[FvM]

For a large dynamic range, constant overtemperature is basically a better method, also widely utilized in thermal conductivity measurements. But the characteristic will be non-linear in any case.

 

[naz83]

Hi all,
My anemometer works fine with pt1000, but when i soldered pt1000 so that it can be mounted on a probe it has stopped working as a sensor anymore, i don know if we can solder a pt1000 or not? any suggestions and also any idea as to how to mount the sensor as the pt1000 is very fragile.
Thanks

 

[grieblm]

Depending on which device you are using it is possible to solder it. If it has leads, you can heatsink the leads closest to the RTD element and solder to the circuit. Surface mount RTDs usually can tolerate soldering temperatures for 10 seconds or so.