Outdoor Temperature with 2441ZTH

[Rod]

I am attempting to use a 2441ZTH Tstat to monitor outdoor temperature. I soldered the external probe in place of the internal temperature sensor as suggested in the forum - which works well. However, when the temperature falls below zero, ISY displays a temperature of 127.5 degrees. It appears the 2441 sends ISY a signed byte with each bit representing 0.5 degrees, so -0.5 is represented as FF. ISY ignores the sign and displays 127.5 (FF/2). A temperature of -1.0 displays as 127.0, -2.0 as 126.0, and so on.

 

If I use the Celsius scale, the negative values are absolutely distinguishable from positive temperatures. However, ISY only allows the temperature to be compared against values of 1-122 degrees. That means I cannot distinguish temperatures between +1C and -6C - a critical range. That deadzone is much colder in Fahrenheit but is still falls in a common temperature range for our climate. Fahrenheit has a second problem of negative temperatures overlapping valid warm temperatures. 

 

A workaround is to use the Climate Module for outdoor temperature. Unfortunately, our nearest weather station is too far away to get an accurate reading. 

 

Has anyone else encountered this problem and found a workaround?

[paulbates]

The insteon protocol is not designed for a wide range of analogue values. The thing I've seen others use are are the CAO wireless tags that include a temp sensor. They can be set up to write temperatures, including outdoors, back into ISY variables via wifi>lan>ISY. Search the forum for CAO and you'll find a number of references

 

 

Paul

[larryllix]

Working at -20C last week.