We tried to measure the dewpoint for Argon and Nitrogen compressed gases which theoretically are at -186degC and -70 degC using the DMP74B dewpoint analyzer, but we are unable to get the accurate reading of the dewpoint.

Wanted a few clarification:
a) If the medium tested for dewpoint have a higher range than the analyzer used, will the analyzer give a lower reading instead as it is beyond the accuracy region?
b) Can dry gases like argon & nitrogen be used to test dewpoint with the Vaisala DMP74B type analyzers?