Dynasonics 701_771C Series Insertion Ultrasonic Flow Meter - Manual (Page 36)

Rev. 12/97 -35- D77X
at zero flow equals 4mA and 20 FPS (6.08 MPS) equals
20mA. The 20mA key allows fine adjustments to be made
to the “span” of the 4-20mA output. To adjust the 20mA
output, an ammeter or reliable reference connection to the
4-20mA output must be present.
Procedure:
1. Either break the present current loop and connect the
ammeter in series (disconnect either wire at the
terminal block labeled 4 -20mA on the Main PCB of the
D77) or, if this output is not being utilized, connect the
ammeter + to the + terminal and – to the – terminal of
the 4-20mA output.
2. Press the 20mA key.
3. With maximum flow moving through the pipe, adjust
the setting count using the arrow keys until 20.00mA is
indicated on the ammeter. The typical count value
range for this setting is between 1450 and 1950.
4. Press ENTER to store the value.
5. Re connect the 4-20mA output circuitry as required.
{2
nd
FUNCT} SS CUTOFF
This entry represents the signal strength cutoff level (low
velocity cutoff). At flow rates below 0.2 FPS [0.06 MPS]
the readings displayed by the D77 are unreliable. By
utilizing the default SS CUTOFF of 100 counts, small
unstable readings at low flow rates will be avoided.
Note: If SS CUTOFF is set to a level higher than the
SIGNAL STR value the meter will not show flow or output
any values.
{2 nd FUNCT} INPUT F.S.
This key is used to select a maximum velocity that the
PART 3 - KEYPAD CONFIGURATION