Dwyer Series PUF - Manual (Page 41)

3: Operating Procedures
37
Converting the measured current to flow rate
Assume the maximum flow rate is F
max
(gal/min) and the minimum flow rate F
min
is ‘0’ (gal/min), as shown.
To calculate the flow rate (gal/min) for a measured current I mA then:
3.8.2 Pulse output
The pulse output can be used in two modes, ‘volumetric’ and ‘frequency’. When operating in the ‘volumetric’
mode a pulse is produced every time a pre-selected volume of liquid passes through the pipe; and when in the
‘frequency’ mode the output is a continuous pulse-train with a frequency proportional to the flow rate (gal/min).
Using the instrument’s menu system, the operator can use the following procedures to:
• Select the pulse output function Off/On/Frequency.
• Volumetric mode – select the output pulse width and volume per pulse.
• Frequency mode – select the maximum pulse frequency and the corresponding maximum flow rate.
Turning the pulse output OFF/ON (volumetric mode)
0-20 mA 0-16 mA 4-20 mA
1. With the instrument operating in the FLOW
READING mode, press the Pulse function key to
access the
PULSE OUTPUT screen.
2. A Pulse output is ON (or OFF) message
appears in the second line of the display.
3. To change the pulse output operational status,
select the
Output menu option then select Off/
On as required.
4. Select Exit and press the ENTER key to return
to the FLOW READING screen.
PULSE OUTPUT DD-MM-YY HH:MM:SS
Pulse output is ON Qxx.xx%
Flow units : gal
Output : On
Vol per pulse : 10.00
Pulse width (ms) : 10
Max Pulse Freq (Hz) : 10.00
Flow at Max Freq : 200.00
Calculated Pulse Value: 20.0
Exit
4 8 12 16 20
F
max
Flo
w
(g
al/m
in
)
I (mA)
F
min
[0-16 mA scale]
[0-20 mA scale]
[4-20 mA scale]
Flow rate
I F
max
F
min
–
( ) ×
20
------------------------------------------- F
min
+ =
Flow rate
I F
max
F
min
–
( ) ×
16
------------------------------------------- F
min
+ = Flow rate
I 4 –
( )
F
max
F
min
–
( ) ×
16
( )
--------------------------------------------------------- F
min
+ =