Dwyer UFC - Manual (Page 26)

3: Operating Procedures
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units by pressing keys 7 (liters), 8 (Gallons, Barrels) or 9 (m³), or change the display to show velocity by pressing
key 4.
If the flow reading exceeds a value of +/-9999 in the current units, then a *10 multiplier will be displayed above
the units and the value displayed will be a tenth of the actual value. Similarly a * 100 and *1000 may be displayed
on very large flow rates.
Once a valid flow reading is obtained, if the pipe conditions change (such that the flow reading is lost) then the
system will automatically rescan to re-establish a stable flow reading. It is important that the instrument is left with
the
FLOW READING screen on the display because the automatic rescan is disabled if any of the other screens
that can be reached from the FLOW READING screen are being displayed.
Note: There will be a delay in the keyboard response if a rescan is in progress when a key is pressed.
3.3 Instrument Calibration
The instrument is fully calibrated before it leaves the factory; however the following adjustments are provided to
allow you to further ‘fine tune’ your instrument to suit local conditions and applications where necessary. Apart
from the ‘zero flow offset’, these adjustments are normally carried out only where the instrument is to be used at a
permanent, or semi-permanent, location.
3.3.1 Adjusting the zero cut-off
This adjustment allows you to set a minimum flow rate (m/s) below which the instrument will indicate ‘0’. The
default setting is 0.1 m/s but you may adjust this value if required.
1. With the instrument operating in FLOW
READING mode, press the Options key to
access the
FLOW READING OPTIONS menu
shown (password required).
2. Select Zero Cutoff (m/s) and press
ENTER.
3. Enter the value for the Zero Cutoff (e.g. 0.06
m/s) then press ENTER.
4. Scroll down to select Exit and press ENTER to return to the FLOW READING screen.
3.3.2 Adjusting the set zero flow offset
The UFC instrument operates by comparing the time taken to send an ultrasonic signal between two transducers
in either direction. A
Set zero flow offset adjustment is provided to compensate for any inherent differences
between the two sensors, noise pick-up, internal pipe conditions etc. It can be used to ‘zero’ the flow indication
under no-flow conditions.
1. Stop the liquid flow.
2. With the instrument in FLOW READING mode, press the Velocity function key and observe the reading
(m/s). Any reading other than 0.000 indicates an offset error and in practice this will typically be in the range
Key Point: If you have adjusted the Zero Cutoff point to anywhere above ‘0’ you
must reset it to ‘0’ before you can observe and adjust the Set zero flow offset, as
its value is very small. Once the Set zero flow offset has been cancelled you can
then reapply the Zero Cutoff if required.
FLOW READING OPTION DD-MM-YY HH:MM:SS
Data review
Zero Cutoff (m/s) : 0.100
Set zero flow (m/s) : 0.000
Damping (secs) : 10
Totalizer : Run
Reset +Total