Teledyne 4220, Installation And Operation Manual, Page: 42 / 198

4220 Flow Meter
Section 2 Programming
2-14
Return to the Setup menu if the unit has not already done so.
This time select ENABLE/ALARM HYSTERESIS from the
menu. Press
Enter . The following will appear:
The HYSTERESIS menu lets you set the range over which the
level (or other condition) can vary before the flow meter responds
to the change.
In the PROGRAM section of the software there are several steps
that require a
change in a condition to make the flow meter
carry out certain actions. For example, step 6 programs the flow
meter to enable (activate) a sampler. In that step, you select a
condition (or set of conditions) that must occur before the
sampler is enabled. You enter a value (level is an example) that
must be met before the enabling occurs.
But what if this value is met and then falls away? It is possible
for a condition to vary rapidly over a narrow range. Without hys-
teresis, the flow meter will turn the sampler off and on
repeatedly, causing a condition known as
chattering , that would
result in very erratic operation of the sampler.
With hysteresis, you can enter a value that will keep the flow
meter from responding to insignificant changes in the enabling
condition. You should select a value for hysteresis that is narrow
enough to allow the flow meter to respond to any serious change,
but broad enough to ignore minor changes that could cause chat-
tering.
The next three menus may not appear, depending on other selec-
tions you make in
Program . They concern alarm/enable hys-
teresis set points for parameter sensing—temperature, pH, and
D.O.
If you want to set hysteresis for any of these items, you should
enable them when you work through the program section, then
re-enter the
Setup section (Hysteresis) and they will appear.
Note that you can have temperature alone, or temperature with
either pH or D. O. You
must have temperature with either pH or
D. O.
Note
You cannot have pH and D.O. at the same time, and selection
of one will prevent the other from appearing on the menus
later.
The following will appear if you are measuring temperature:
The following will appear if you are measuring pH:
LEVEL ENABLE/ALARM
HYSTERESIS
X.XXX FT (or other units of measure)
TEMPERATURE ENABLE/ALARM
HYSTERESIS
XX.XXX DEG F (or C)
pH ENABLE/ALARM
HYSTERESIS
X.XXX pH