Vaisala PTB220 - Manual (Page 57)

C HAPTER 6________________________________________________________________ OPERATING
V AISALA _________________________________________________________________________ 51
PULSE mode
In the PULSE output mode, the barometer requires a trigger pulse
from the host system. In this case, the barometer must be powered-up
separately and the pulse trigger signal must be given to the barometer
after the settling time has elapsed. The trigger signal must be a TTL
level signal. The pulse output is triggered at the falling edge of the
TTL trigger signal from TTL HIGH (5 VDC) to TTL LOW (0 VDC).
The pulses are output at TTL level voltages.
NOTE See Appendix on page 83 for complete information on how to use the
pulse output mode of the PTB220 series barometers.
Operating the local display and keyboard
The display and keyboard of the PTB220 series barometers is a
configuration option. The LCD display has on/off selectable backlight
for better readability at any light conditions. The two rows of the
display can be defined to indicate different kind of information (see
Software settings, DFORM command on page 22). Besides, the
measured pressure reading itself, the display can contain e.g. the
WMO three-hour pressure trend and pressure tendency code. Error
messages will be indicated on the second row, should a problem occur
in the barometer.
The following basic rules apply to the use of the keyboard:
1. Use ENT key to enter the MENU mode or to acknowledge a
new selection.
2. Use CL key to clear a parameter value in order to input a new
one or to revert to the original display.
3. Use arrow keys to make a selection between functional
alternatives or to enter a new parameter value after clearing the
previous one with CL key.
4. Entering a new parameter value may require each character of
the value to be entered and acknowledged separately. Any
previous value is deleted with the CL key. Scrolling the display
with the arrow keys will then cause one of the following
characters to appear at a time:
space ' '
dash ' - ' decimal point ' . ' number '0 ... 9'