Vaisala PTB220 User Manual download pdf (Page 89)

APPENDIX D ____________________________________________________ PULSE OUTPUT MODE

VAISALA _________________________________________________________________________ 83

APPENDIX D PULSE OUTPUT MODE

NOTE

The pulse output mode can be used with hPa/mbar pressure units only.

The pulse output mode of the PTB220 series barometers is useful

when no serial interface is available in the host system. A standard

pulse counter interface is all that is needed to count the number of

pulses output by the barometer. The host system must create a trigger

pulse for the barometer, and reset and open the gate of the counter to

be able to receive the pulses. The pulse counter must be capable of

measuring pulse rates up to 5 kHz or 50 kHz.

The trigger pulse must be a TTL level signal. The pulse output of the

PTB220 series barometers is triggered at the falling edge of the trigger

pulse. The pulses are then output within 1 to 100 ms depending on the

internal status and settings of the barometer. The recommended

procedure is to first reset and open the gate of the counter and then to

give the trigger pulse to the barometer. The gate-open time must be

long enough to allow enough time for all pulses to be output by the

barometer. The pulse output and trigger input signal levels are at

5VDC level when the barometer is outputting no pulses. The trigger

pulse can be a positive pulse or negative pulse but its duration must be

minimum 1 µs.

The figure below illustrates the timing principle of pulse output mode:

output pulses

counter gate open

trigger pulse min. 1 us, trigger at falling edge of the pulse

pulse output starts within 1...100 ms from trigger

1 2 ... 84 85 86 87 88 89 90 91 92 93 94 ... 112 113

No comments

Vaisala PTB220 User Manual Page 89