Update:
In the scenario described in my initial post:
– The SSR Relay +/- terminals were disconnected
Seeing different behavior once the SSR terminals were connected, I have these additional findings:
– When both SSR terminals are disconnected, temp error is about 30-40 degrees C [this is the ‘wildy incorrect values reported previously]
– When the – SSR terminal is connected, error is reduced to ~15-20 degrees C
– When both the + and – SSR terminals are connected, error is reduced to 10-12 degrees C
[The two leads from the SSR terminals are approximately 12 inches in length; perhaps they are functioning as an antenna for noise?]
Finally, I have verified that when the UI is NOT connected to the OsPID, the temperature error disappears (is less than 1 degree C).
Although my 10nF capacitor has not yet arrived, I’ve added a second 22nF cap and can also report that now the temp error I get when powered by the AC-DC convertor is similar in magnitude to the error I see when the UI is connected (10-12 degrees C).
– scott
