Teledyne 4220 specification

4220 Flow Meter

Section 2 Programming

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:

LEVEL ENABLE/ALARM

HYSTERESIS X.XXX FT (or other units of measure)

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