Thanks for the comment everyone. However, this is exactly what I did so far - refreshed the value periodically. This is problematic, because the measurement is slow, and in worst case, if the user wants to switch the lamp on (by triggering a DI switching a relay) he will see the response of his action about two seconds later. This is not fine. If the request was temperature measurement, and the user knows, that the action takes some time, this is not a problem, but an implicit delay is not OK. This is why I want to trigger the temperature measurement explicitely, and don't run it periodically. If the user requests the data, should get the data, otherwise performing a measurement is unneccessary.
Thank you once again!
Zsolt
