HyQuest Solutions Pty Ltd
Point Velocity Display - Model PVD100
©
Copyright
16
Issue 1.00 4 Apr, 2007
DWELL?
YES
CAT
- - -
- - - - - -
4.3.11 Dwell
Measurement
Using the Function button scroll to the “Dwell ?” menu and
press Select to move the arrow to Yes, and then press the
ON/OFF button to enter the dwell function. Refer to
Appendix B Measuring Meter Dwell
for a further
explanation of this function.
The opening display for the special operating function called ‘DWELL’ is shown. This
function measures the dwell angle (ratio of meter contact time to the total time for a single
rotation) for a meter contact and is useful for making
adjustments to a cat whisker type meter in the field. For a cat
whisker contact head, the optimum adjustment is 60º or a
single meter cup width (US Geological Survey Price AA or
Pygmy meter). A variation to an adjustment of +/- 10% is
acceptable. For this function, (3) measurements are taken from
a rotating meter. The results of the measurement are displayed
in whole degrees of dwell. The measure of dwell angle for the magnetic head contact does
not apply but can be performed. To perform the measurement, the following steps are used :
1. Before enabling this function from the menu, select the type of contact head, i.e
magnetic head or cat whisker head contact. This is done from a different menu.
2. After selecting the type of meter contact head, when the ‘DWELL’ measurement
function is enabled, the opening display presentation will show the type of meter
contact selected to make the measurement.
CAT
is shown when a cat whisker
head is chosen and
MAG
is shown when a magnetic head contact is chosen.
3. From the ‘DWELL’ measurement function display as shown above, free spin the
meter at a rate of about 2 rotations per second.
4. Depress the ‘SELECT’ key.
5. As each measurement is taken, a whole number display of dwell angle (in degrees)
will be shown. If no contact closures are detected within a 4 second period, the
display will read “NO DWELL”. Conversely, if the contact closures are too long,
the display will read “EX DWELL” indicating exceeded dwell.
6. To repeat the measurement, simply spin the meter and depress the ‘SELECT’ key.
7. During the measuring of dwell angle, the ‘STATUS’ indicator will flash ‘
red’
at
each detected contact closure to show a cat whisker head is selected and the
display shows
CAT
. If the STATUS indicator is flashing
green
during the
measurement, the meter selection is Magnetic Head and the display will show
MAG
. Again, select the type of meter contact head before selecting this function
to measure the dwell angle of the meter.
8. To exit from this function, simply depress the ‘ON/OFF’ button.