Use of ADS1118 with type B thermocouple

Samuel,

I don't know of anyone that is using the ADS1118 with a b-type thermocouple.With the full scale range of +/-0.256V, this gives you an LSB size of 7.8uV, which is a bit large for such a small response. If you do go with the ADS1118, there are a few references to look up. There's an evaluation module (which is more like a demo. There is also an MSP430 booster pack. Finally there is a precision design. Note that all of these are put together with k-type thermocouples.

I'll include some other reading material for the ADS1118:

Since you are using the b-type thermocouple, a better selection might be the ADS1147/8 or ADS1247/8. It will have more resolution with the larger gain settings. There are also similar EVMs and other reading material associated with it:

Joseph Wu

Thanks Joseph.

The  ADS1220  seems to be a perfect solution to our temperature measurement needs.

We will probably purchase the ADS1220EVM.

Are there any application notes for temperature measurement or other low-signal with the 1220? 

Do you know if there is an option to also get a few samples to test with our design?

samtal

To add to my prev answer:
I have seen the attached application note, to which I have a comment to add: The AN shows the TC measurement with an external RTD reference measurement, while stating that TC must have such reference temperature reading.
Well, this is not necessary when using thermocouple compensation wires that move the reference to the board, enabling the use of the chip's internal temperature sensor.
I wonder: Is there a reason to neglecting the commonly used TC compensation wires ?

Sam,


You can find a few ADS1220 designs if you search the TI website:

www.ti.com/.../refdesignsearchresults.tsp

If you want a few free device samples, you'll need to give a company address. Click the "Request Sample" button at the following website:

www.ti.com/.../samplebuy;tisearch=Search-EN-Everything

As for your latest post, I'm not quite sure what you are asking. You're referring to the thermocouple based application where they use an RTD based cold-junction compensation. I think the issue is that the cold junction and the board may not be at the same place or even the same temperature. Even if the ADC uses its internal temperature sensor, you still may need to make a remote temperature measurement (in this case, using a separate RTD measurement).

If that's not what you're asking about, post back and I can comment again.


Joseph Wu