Changing Calibration Parameters - GF PF220 V2 Betriebsanleitung

Operating Instructions
8.3

Changing calibration parameters

The flowmeter is fully calibrated before it leaves the factory however, the following adjustments are provided to allow you to fur-
ther 'fine tune' your instrument to suit local conditions and the user's 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.
8.3.1 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.
FLOW READING OPTION
Data review
Zero cutoff (m/s)
Set zero flow (m/s)
Damping (secs)
Totaliser
Reset + Total
8.3.2 Adjusting the set zero flow offset
The flowmeter operates by comparing the time taken to send an ultrasonic signal between two transducers in either direction.
A 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.
The sign of the zero-flow volumetric reading or the velocity is always the same irrespective of the direction of flow because the
ZFO is a function of the sensor match. If the ZFO offset is significant, and the sensor leads are reversed, one of the following
procedures must be followed again to ensure continued accurate results.
NOTICE
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.
There are two methods for setting the zero-flow offset: the in-built Zero Flow Offset feature (ZFO) or by manual intervention.
Method 1: Using the Zero Flow Offset (ZFO)
Using this method, the unit runs for a period of time and collates the data and averages it over this period. The zero-flow cut-off is
automatically removed while running the test and returned to its previous value afterwards. Likewise, it will remove any existing
ZFO automatically and either replace or restore it. To use the ZFO feature:
Setting Zfo
Running Average
Time Remaining
Set Zero Flow. .
Exit
DD-MM-YY HH:MM:SS
: 0.00
: 0.00
:
10
: Run
DD-MM-YY HH:MM:SS
-2.24 1/min
0 sec
1. Select View / Edit Site Data from the MAIN MENU.
2. Use the UP/DOWN arrow keys to select Cutoff Velocity.
Press the ENTER key.
3. Edit the value as required and then press the ENTER key.
4. Scroll down to select Exit and press the ENTER key to
return to the View/Edit Site Data menu
1. Stop the liquid flow.
2. With the instrument in FLOW READING mode, press and
hold the 0 (zero) key for at least two seconds.
3. In the Set Zero Flow screen, set the damping time and
the measurement time. The recommended measurement
time should be in the region of 60 to 120 seconds, but
much longer periods are possible if significant drift in
measurements have been noted over a longer period.
4. Select Continue..
5. On the Setting Zfo screen, the Running Average is updated
every second. When the measurement has completed, a
loud ½ second beep will be heard and the countdown will
stop.
6. You may now select Set Zero Flow.. if desired. It should be
noted that you may select this setting at any time before
the measurement is complete if you are satisfied that the
average reading is sufficiently accurate.
Operation of the device
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