DP Transmitter Sees the Light  Rainy days depress a DP
transmitter; E-mailing a prospective engineer; and a new
puzzler: Hair-trigger temperature loops  Share Print Related RSS
: We had smart answers about the dumb DP transmitter puzzler in
the March issue from Bob Cameron and Paul Fielding. Paul also
had an interesting anecdote...and antidote for boredom.  Paul:
Sounds to me like the dumb transmitter has a zero shift due to
ambient temperature change. The smart DP has internal
compensation for ambient temperature change. Actually, about 30
years ago, one of our service engineers finally solved a similar
problem. A low-range (draft) transmitter would change output on
a somewhat regular schedule but after a while return to being
OK. Both field and bench calibration checks showed it to be OK.
On one of several trips he made to this plant, a rainstorm
occurred after lunch on a bright sunny day. The transmitter,
which was bathed in sunlight in the morning, suddenly shifted
after the rainstorm started. Only the