17
..... Additional setup menus within the FLOW submenu
F
IGURES
3.10-A
THROUGH
3.10-C (
LEFT
TO
RIGHT
,
TOP
TO
BOTTOM
)
3.
Low Flow Cutoff
setup menu (34): When a zero flow condition occurs (for example, as the result of a
pump being shut off), internal sloshing, check valve leakage, and other fluid movement can prevent
the flowmeter from reading total zero. This phenomenon can result in totalizer errors. Minimize these
errors by entering a low flow cutoff, which drives the flowmeter to zero for flow rates at or below the
specified value. If the flow rate falls below the low flow cutoff value, the indicated flow rate is driven to
zero and the totalizers stop incrementing; this is the case regardless of flow direction (Figure 3.10-D,
below).
For example, if you enter a low flow cutoff of 0.1 ft/s (.03 m/s), the flowmeter is driven to zero for flow
rates less than 0.1 ft/s in the positive direction and greater than -0.1 ft/s in the negative direction
(Figure 3.10-E, below).
F
IGURES
3.10-D (
LEFT
) & 3.10-E (
RIGHT
)
4.
Low Signal Cutoff
setup menu (35): Empty pipes or solids, bubbles, or voids in the flow stream may
cause temporary drops in signal strength and erroneous readings. Minimize the effect of these
dropouts by setting a low signal cutoff, which drives the flowmeter to the loss-of-signal (LOS)
condition. The low signal cutoff should be set at the minimum acceptable signal amplitude.
a.
Access the
Low Signal Cutoff
setup menu
(Figure 3.10-F, page 18)
.
b.
Enter the low signal cutoff and press
ENTER.
The value for the low signal cutoff should usually be set at approximately one-
half of the value of the signal strength present under flow conditions. Typically,
signal strength is not significantly affected by flow rate.
c.
Select one of the following
(Figure 3.10-G, page 18)
:
•
ZERO
: Drop the reading to zero during LOS condition
•
HOLD
: Hold the last valid reading during LOS condition for about 3 seconds
