HyQuest Solutions Pty Ltd
Point Velocity Display - Model PVD100
©
Copyright
22
Issue 1.00 4 Apr, 2007
S
–
Start a measurement:
Begins a measurement at the first contact closure detected.
Number of contact closures and elapsed time counts are accumulated. At the first
contact closure, the
PVD100
begins sending the accumulated contact closures and
elapsed time counts through the serial port every second. The first data string
transmitted through the serial port begins the start of the measurement interval with
the meter contact closure count tally and elapsed time tally of ‘0’. Note that when
this command is received by the
PVD100
, it automatically performs a calibration
then monitors the input for meter contact closures. Following is the output data
format sent to the externally connected device at the 1-second output rate:
dnn,xxxx_
d
= preamble for indicating display data
nn
= number of meter contact closures, transmitted in HEX ASCII
(hexadecimal notation)(i.e. 0-9,A-F)
,
= delimiter
xxxx = counts of elapsed time measured as 0.003333 seconds/count,
transmitted in HEX ASCII (i.e. 0-9,A-F) while in Normal mode
and 0.03333 seconds/count while in Slow mode.
_
= space
This data format that is transmitted to the externally connected device can be used
to display elapsed time and velocity while the measurement is being performed.
At the end of the measurement interval or if the ‘
T
’ command is received, the
PVD100
sends the last tally of accumulated counts and time in the following
format:
fnn,xxxx
or
enn,xxxx
f
= final data, no detected faults
e
= final data, error detected during measurement;
restart the measurement
The measuring interval is based on the user selected measurement time. When the
measuring interval has been reached, (or the T command is received) the
PVD100
,
upon the next meter contact closure, will send the final data for that measurement.
If there is no contact closure detected when the measurement interval has been
reached, the
PVD100
will continue to send data and the user must send the ‘I’
command to abort the function. Note that the meter contact number, nn, is limited
to a total of 255 counts (hexadecimal notation ‘FF’). If more than 255 counts are
detected throughout the measurement interval, the count will rollover to ‘00’ and
continue to accumulate counts. No fault condition is set if this occurs. This allows
for continuous counting in excess of 255 counts occurring during the measuring
interval. External processing software can easily detect this condition and process
total meter counts when the measuring interval is completed. The same condition
occurs for the elapsed time tally. This permits an elapsed time count of 218
seconds for a measuring interval before the count rolls over to ‘0000’.
