ADS Environmental Services Portable FlowShark Pulse QR 775006 A2 - Manual (Page 158)

Parameter Settings 6-59
min. + max. value
This parameter defines the range within which the Portable FlowShark Pulse will
measure flow velocity.
Measurement range for flow velocity
h_crit
A sensor cannot measure flow velocity once the depth falls below a certain threshold
referred to as h_crit. The value of h_crit is determined based on the construction of
the sensor and method of measurement. This information is stored in the sensor
memory.
The Portable FlowShark Pulse automatically receives the stored h_crit values from
the sensor following the initialization process.
The sensor memory stores the following h_crit values based on the sensor type:

POA sensor 2.6 inches (65 mm)

CSM sensor 1.2 inches (30 mm)
The Portable FlowShark Pulse will now use the h_crit values from the sensor;
however, these values will not be available through the Cal > Flow velocity > h_crit
menu at this time. This menu will still indicate 0.000 for these values. However,
once you manually modify the h_crit, the Cal > Flow velocity > h_crit menu will
display the corresponding modification.
The unit will adjust the h_crit values in the background automatically if the mounting
height of the velocity sensor is changed.
Following start-up, the Portable FlowShark Pulse will use the initial values from the
Manning-Strickler table (available through CAL > Flow velocity > v-crit
determination > Manning-Strickler) until the readings reach the stored h_crit value.
Flows ranging from 3.5 to 4.7 inches (9 to 12 cm) that exhibit a downward trend will
cause the unit to recalculate the application coefficient for h_crit (automatically
selects YES). Then, the unit will continue to estimate velocity when depth is below
h_crit using the calculated application coefficient based on Manning Strickler.
Parameter h_crit