I am using the ADT7470 and the TMP05 in a daisy chain configuration and there are five sensors. I get temperature readings that intermittently vary by huge amounts and then return back to the expected temperature.
Please refer the attached documents for more details.
Block diagram - ADT7470_TMP05_Block_Diagram.pdf
Problem Report - ADI Enginnering Zone.pdf
Circuit diagram - TMP05 Daisy Chain Temperature Sensors.PDF
First I have to commend you for providing decent documentation right out of the chute.
Sometimes we get: "I hooked your part up and it doens't work, why".
Although you said it doesn't do it when the 250 Wt. transmitter is off, I would not completely eliminate
RFI. Is this a repeater site with other transmitters in the area?
The fact that it is intermittent and varies, makes me think your digital timing is off a little bit.
Look at all the signals zoomed in with respect to set up and hold times. The temp sensors
are not designed to drive long cables at high speeds. Shielded twisted is good for RFI, but
adds inductance and capacitance.
At the moment we are testing and there is only one transmitter. In the real application also there will be one transmitter per site and will not consist of any repeaters. I am in the process of doing more testing and will keep you updated.