Technical Manual
Page 23
CODEL
OPS.109
Issue : B
Rev. : 1
Date : 23/10/13
Doc. i/d : 0109/6
Ref. : 090028
Cross Sectional Area
The cross sectional area in m
2
currently being used to calculate the volumetric flow.
Data Rate
Data Acquisition Rate of Measurement
The system operates by reading and storing the data from the channel
‘A’ transducer at accurately timed
intervals varying from 0.5 milliseconds to 4 milliseconds. A window of 256 readings provides the basis for the
correlation measurement. The data rate thus determines the time frame of the correlation window from 128
milliseconds at a data rate of 0.5m/sec to 1 second at 4 milliseconds data rate. At a transducer separation of 1m
a time of 1 second gives a minimum measured velocity of 1m/sec.
The data rate also provides the resolution for the time measurement. The most sensitive resolution of 0.5msec
is required for the highest velocities but the correlation window of 128msec only allows for a minimum velocity of
8m/sec to be measured. For this reason the data rate selection is usually operated in auto mode where the
analyser itself selects the correct data rate for the flow conditions prevailing at that time. This enables the
working range of the instrument to extend from 1m/sec to over 50m/sec.
Lead Channel
‘A’ or ‘B’ determines which of the transducers is configured to be the upstream detector.
Channel
‘A’ is always defined as the upstream or lead transducer. Depending on the wiring channel ‘A’ may be
either transducer 1 or transducer 2. It is necessary to select the channel
‘A’ device from transducer 1 or
transducer 2.
7.6.3. Averages
Selecting this option will display the times set for each of the four averaging stacks.
7.6.4. Output
The base, span and averaging of the analogue output are displayed from this option for both outputs 1 & 2.
7.6.5. Alarm
A changeover relay contact output is available to indicate a high flow level. The level at which this output is
operated, and the averaging stack, from which the flow value is obtained, may be examined from this display.
This alarm may also be configured as a cal-in-progress indicator.
A second changeover relay contact output is available to indicate a low flow level.
7.6.6. Plant Status
When plant status is OFF (terminals 28 & 29 shorted together), the minutes, hours and days averaging stacks
do not update - the plant is considered to be not running properly and if this data is stored the averages will give
false (diluted) readings.
This function may be used to ensure data is only collected when the plant is fully operational. The logic input
can be used to determine plant status ON or OFF. The plant status and its governing factor may be viewed from
this display.
The plant status logic input may also be configured as a cal-initiate input (See section 7.6.8.Cal Config).
7.6.7. Clock
The current time and date are displayed from this option in the form :