Vaisala PTU300 - Manual (Page 71)

Chapter 4 _________________________________________________________________ Operation
VAISALA ________________________________________________________________________ 69
Using Serial Line
Pressure 3h trend and tendency reading is also available through serial
line. Key in the lines below:
>form "P=" p "trend=" p3h "tend=" a3h #r#n
OK
>send
P= 1024.7trend= 0.8tend=1
The last line shows the values.
For more information on the Form command, see the section Changing
Quantities and Units, starting on page 101.
Missing Trend
The PTU300 series barometers output a code "*" when the pressure
tendency has not yet been calculated - that is, less than three hours have
elapsed since the power-up of the barometer. The absence of the pressure
trend is indicated in a similar manner, too.
NOTE When the P
3H
tendency is chosen as a display quantity, the PTU300 logs
actual measured pressure, instead of trend or tendency value.