Alicat PCU Portable Calibration Unit - Manual (Page 12)

12
Select Main
>
LCD Contrast (10) . 10
PVM DBand (0.5 %
FS )
PRESS Avg
(008) . . . 008
FLOW Avg
(100) . . . . 100
UP DOWN Misc
Figure 7. Miscellaneous Display
LCD Contrast: The Liquid Crystal Display Contrast can be adjusted between 0 and 30 with zero being
the lightest contrast and 30 being the darkest contrast. To change the contrast, press the “Select”
button in the upper left hand corner of the display until the cursor arrow is in front of the words “LCD
Contrast (X)”. Then using the UP and DOWN buttons at the bottom of the display, change the contrast
value as desired. The change is immediate and the effect can be monitored as the value is changed.
Display Zero Deadband: Zero deadband refers to a value below which the display simply jumps to
zero. This deadband is often desired to prevent electrical noise from showing up on the display as minor
flows or pressures that do not actually exist, especially in high noise (electrical) environments. This
display deadband does not affect the analog or digital signal outputs — there is no zero deadband on the
output signals. The display zero deadband can be adjusted between 0 and 3.2% of the Full Scale (FS)
of the sensor. PVM refers to Pressure, Volumetric Flow and Mass Flow, the three parameters to which
the deadband applies. To adjust the display zero deadband, press the “Select” button in the upper left
hand corner of the display until the cursor arrow is in front of the words “PVM DBand (X %F.S.)”. Then
using the UP and DOWN buttons at the bottom of the display, change the display zero deadband value
as desired.
Pressure Averaging: It is sometimes advantageous to apply an averaging factor to the pressure output
(and display) to make it easier to read and interpret rapidly fluctuating pressures. Pressure averaging
can be adjusted between 1 (no averaging) and 256 (maximum averaging). This is a geometric running
average where the number between 1 and 256 can be considered very roughly equivalent to the
response time constant in milliseconds. This can be very effective at “smoothing” high frequency process
oscillations such as those caused by diaphragm pumps. To adjust the pressure averaging, press the
“Select” button in the upper left hand corner of the display until the cursor arrow is in front of the words
“PRESS Avg (XXX)”. Then using the UP and DOWN buttons at the bottom of the display, change the
pressure averaging value as desired.
Flow Averaging: It is sometimes advantageous to apply an averaging factor to the flow output (and
display) to make it easier to read and interpret rapidly fluctuating flows. Flow averaging can be adjusted
between 1 (no averaging) and 256 (maximum averaging). This is a geometric running average where
the number between 1 and 256 can be considered very roughly equivalent to the response time constant
in milliseconds. This can be very effective at “smoothing” high frequency process oscillations such as
those caused by diaphragm pumps. To adjust the flow averaging, press the “Select” button in the upper
left hand corner of the display until the cursor arrow is in front of the words “FLOW Avg (XXX)”. Then
using the UP and DOWN buttons at the bottom of the display, change the flow averaging value as
desired.