Dynasonics 701_771C Series Insertion Ultrasonic Flow Meter - Manual (Page 35)

Rev. 12/97 -34- D77X
at zero flow equals 4mA and 20 FPS (6.08 MPS) equals
20mA. The 4mA key allows fine adjustments to be made
to the “zero” of the 4-20mA output or allows offset to be
placed on the 4-20mA output. To adjust the 4mA 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 4mA key.
3. With no flow moving through the pipe, adjust the
setting count using the arrow keys until 4.00mA is
indicated on the ammeter. The typical count value
range for this setting is between 3350 and 3850.
4. Press ENTER to store the value.
5. Re connect the 4-20mA output circuitry as required.
{2
nd
FUNCT} VEL ADC
Press VEL ADC to display the raw analog to digital
converter counts that are being processed by the
microprocessor. This count value will vary linearly with
flow rate from 0000 at zero flow rate to 1024 at maximum
full-scale flow rate. No modifications of this count can be
made, this display is for diagnostic purposes only.
{2 nd FUNCT} BLANKING
This key is unused.
{2 nd FUNCT} 20mA
The 4-20mA output on standard D77 flow meters is scaled
PART 3 - KEYPAD CONFIGURATION