Model 2000 Flow Computer Instruction Manual
2.0 GENERAL DESCRIPTION
Model 2000 issue 21 Page No
26
2.4.2.3. METER LINEARISATION
A facility is provided which gives the option to linearise the meter line flow rate value. The options are selected using the
parameter Lin Corr . on the Ultrasonic set-up page and are:-
off No correction
20 pnt Linearity correction using 20 point interpolation.
The meter is characterised by entering up to twenty co-ordinates for flow and corresponding error values which are stored in
the Model 2000 memory. A linearity correction applied to the corrected flows by interpolating between the co-ordinate points.
Correction is applied to the uncorrected flow rates, uncorrected and corrected total flows.
The value entered into the %Qmax n data location is in % of maximum flow (Q max.) of the meter, this figure can range from
– Qmax to + Qmax to allow for different linearity in the opposite flow direction and the value entered in the corresponding
%Er.rd n location is the % error of reading. If the output from the meter is less than the actual flow through the meter then
the error is entered as a negative value.
%Er.rd n = the % error in reading of the meter flow rate at %Qmax n flow rate. n is an integer between 0 and 19
The lowest value of flow in this case nearest to –Qmax (or nearest to zero flow if the flow is only in the +ve direction) must be
entered at the position n = 0. The rest of the data points must be entered in ascending value of Q up to the top point. If it is
required to enter less than the maximum 20 points then any unused data positions must be set to invalid data by entering a –
sign with no numbers.
2.4.2.4. METER ALARMS
A number of separate alarm conditions in the Ultrasonic Meter can be recognised and indicated as follows:-
2.4.2.4.1. ACCOUNTABLE METER ALARMS
An accountable alarm will be indicated if any of the following conditions occur:-
If no valid communication is received from the meter for 5 consecutive seconds after this time the flow rate will be
set to zero.
If the number of acoustic paths set in the Model 2000 is different from number indicated by the meter.
If an invalid floating point number has been received from the meter.
If the Security bit in the Meter Status word is set.
If the meter is operating in reduced accuracy conditions as follows:-
Level 1 type All Swirl paths are functioning within limits
and
All Axial paths are in an efficiency alarm
Continue to display and use values from Meter.
Level 2 type If one or more Axial paths is functioning within limits
and
One or more Swirl paths are in an efficiency Alarm
Continue to display and use values from Meter.
NOTES Level 1 and Level 2 only apply to 3, 4 and 5 path meters
For a 3 path meter Paths 1 and 3 are Swirl
Path 2 is an Axial
For a 4 path meter Paths 2 and 3 are Swirl
Paths 1 and 4 are Axial
For a 5 path meter Paths 2 and 4 are Swirl
Paths 1, 3 and 5 are Axial
2.4.2.4.2. NON-ACCOUNTABLE METER ALARMS
An non-accountable alarm will be indicated if any of the following conditions occur:-
If % efficiency for any acoustic path X is below pre-set limit.
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