Vaisala PTB220 - Manual (Page 37)

C HAPTER 4_____________________________________________________________ COMMISSIONING
V AISALA _________________________________________________________________________ 31
x = pressure reading (in current unit)
This command is used to define the maximum pressure difference
between the pressure readings from different pressure transducers
(P1/P2 or P1/P2/P3). If the defined value is exceeded, the relevant
digits in the ERR field (see FORM command) will change from 0 to 1.
It is recommended to use the ERR field as part of the FORM
command definition, if there are two or three pressure transducers in a
PTB220 series digital barometer. More than one ´1´ in the ERR field
indicates that the pressure reading output of the barometer is not
reliable.
Following basic cases may occur for barometers with two or three
pressure transducers (only the differencies found between the readings
from the pressure transducers are important):
Two transducers: Three transducers:
P high
P low
Pdmax ?
P high
P low
P middle
Pdmax ?
Pdmax ?
For an acceptable measurement crucial conditions are:
- two transducers: P high - P low ≤ Pdmax
- three transducers:
P high - P middle ≤ Pdmax and P middle - P low ≤ Pdmax.
The factory setting for Pdmax is 1 hPa.
Example of setting the limit to 0.5 hPa:
>pdmax <cr>
Pd max
: 1.000 ? 0.5 <cr>
>
Examples of exceeding the Pdmax limit in case of two and three
pressure transducers:
>form <cr>
4.2 P " " UUUU #r #n
? 4.2 P1 " " P2 " " P " " UUU " " ERR #r #n <cr>
>send <cr>
1020.30 1020.32 1020.31 hPa 00
>send <cr>
1020.30 1022.30 1021.30 hPa 11