Teledyne 4250, Installation And Operation Manual, Page: 45 / 204

4250 Flow Meter
Section 2 Programming
2-17
If there is a number greater than zero displayed for signal
strength , the following is generally indicated:
1 = a very weak return signal; 100 = a very strong return signal.
Numbers from 10 to 90 are normal, and numbers of 50 to 90 are
typical for sewers.
If there is a number greater than zero displayed for spectrum
strength , the following is generally indicated: Below 25, the
area-velocity return signal is very noisy. A number near 100 indi-
cates the return signal is very clear. The typical range in most
installations is from 40 to 100.
There are two important things to remember when interpreting
these numbers:
• Is the current velocity value on the display accurate?
• Are these two numbers fairly consistent from one
reading to the next?
If the level/flow readings are valid, you can assume the system is
working and the signal and spectrum percentage values dis-
played here should be adequate. The values should not change
more than 25% from one reading to the next. By contrast,
numbers that vary widely from one reading interval to the next
are indications of an unstable installation, and you should
recheck the level/flow measurement.
If you press Enter again, the flow meter will display the system
voltage:
This value should be from 10.5 to 13.5 (volts DC). Note that if you
do not press
Enter after the first diagnostic menu appears, the
flow meter will automatically advance the display through the
next two screens and finally revert to the
Setup menu after a
short time-out.
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
SUPPLY VOLTAGE:
XX.X
YSI SOFTWARE REV:
XX.X
LEVEL ENABLE/ALARM
HYSTERESIS
X.XXX FT (or other units of measure)