Micronics portaflow 220, User Manual

Page: 23 / 44

3: Operating Procedures
Portaflow 220 User Manual
19
(Issue 1.0)
3.5 Instrument Calibration
The Portaflow 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 application where necessary.
Apart from the zero flow offset adjustment, these are normally carried out only where the instrument is to be
used in a permanent or semi-permanent location.
3.5.1 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 0.02 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.
3.5.2 Adjusting the set zero flow offset
The Portaflow 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 ±0.005m/s (possibly higher on smaller diameter pipes). If a greater figure is shown it is worth
calibrating the offset to obtain a more accurate result. Continue as follows:
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.
FLOW READING OPTION DD-MM-YY HH:MM:SS
Data review
Zero Cutoff (m/s) : 0.00
Set zero flow (m/s) : 0.00
Damping (secs) : 10
Totaliser : Run
Reset +Total
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 calibrated you can then reapply
the
Zero Cutoff
if required.
3. Press the
Options
key to access the
FLOW
READING OPTION
screen shown.
4. Select
Set zero flow (m/s)
and press
ENTER
.
5. Press
ENTER
on the subsequent screen to
accept the change, which will return you to
the screen shown.
6. Scroll down to select
Exit
and press
ENTER
to return to the
FLOW READING
screen.
FLOW READING OPTION DD-MM-YY HH:MM:SS
Data review
Zero Cutoff (m/s) : 0.00
Set zero flow (m/s) : 0.00
Damping (secs) : 10
Totaliser : Run
Reset +Total