4230 Flow Meter
Section 2 Programming
2-16
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, 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 briefly and then falls away? It is
possible for a condition to vary rapidly over a narrow range.
Without hysteresis, the flow meter would turn the sampler off
and on repeatedly, causing a condition known as chattering,
resulting in very erratic operation of the sampler.
With hysteresis, you can enter a value that will keep the flow
meter from responding to small changes in the enabling con-
dition. Select a value for hysteresis narrow enough to allow the
flow meter to respond to any significant change, but broad
enough to ignore minor changes that could cause chattering.
Press Enter again and the following will appear:
The next three menus may appear or not, depending on selec-
tions you made earlier in Program. They concern alarm/enable
hysteresis 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. You
can measure temperature alone, or temperature with either pH
or D.O. You cannot measure either pH or D.O. without mea-
suring temperature.
Note
You cannot measure pH and D.O. at the same time, and selec-
tion 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:
FLOW RATE ENABLE/ALARM
HYSTERESIS X.XXX CFS (Or other units of measure.)
TEMPERATURE ENABLE/ALARM
HYSTERESIS XX.XXX DEG F (or C)
pH ENABLE/ALARM
HYSTERESIS X.XXX pH
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