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Reference, Installation, and Operations Manual Section 6: Meter operation
3-9000-743 Rev S June 2013
Average weighted sound velocity 189
Optional AGA10 sound velocity calculation and comparison
The Daniel Mark III Ultrasonic Gas Flow Meter offers an option to calculate the sound velocity
(using AGA10 equations and gas property data) and compare the result to the meter-measured
sound velocity on an hourly basis. This feature is enabled via the AGA10Key (see Section 4.1.6).
The gas property data required for using this feature can be specified via data points or
optionally read from a Daniel GC (see Section 6.1.16). The AGA8 Detailed Method must be
selected (via the HCH_Method data point, see Section 5.6.14) in order for the AGA10
calculations to be performed (as the AGA10 calculations require AGA8 Detailed method
calculation intermediate results).
Every five seconds the meter updates the AGA10-calculated sound velocity. This value is
readable via the AGA10SndVel data point and the calculation status value is readable via the
AGA10SndVelStatus data point. The status values are as listed in the table below:
Over the course of an hour (starting from the top of the hour), the meter calculates the average
measured sound velocity (the average of the average weighted sound velocity) and the average
AGA10-calculated sound velocity. At the end of the hour, the two averages are compared; the
comparison error (%) is readable via the SndVelCompErr data point.
Note that the comparison error is only calculated at the end of the hour if during the hour all of
the following are true:
• no AGA10 sound velocity calculation errors occurred (i.e., AGA10SndVelStatus always
equal to 0),
• the measured flow velocity was always above the minimum sound-speed-check flow
velocity (specified via the SndSpdChkMinVel data point which has a default value of
1 m/s), and
• the measured sound velocity was always valid (as indicated by the QMeterValidity data
point).
Table 6-2 AGA10 calculation status
AGA10SndVelStatus
Value
Description
0 Calculation OK (no errors).
1 Calculation not performed as the feature is not enabled
(
see Section 4.1.6). AGA10SndVel is set to zero.
2 Calculation not performed as the selected AGA8 method is not the
Detailed method (HCH_Method not set to Detailed Method(3)).
AGA10SndVel is set to zero.
3 Calculation not performed due to invalid AGA8 calculation results.
AGA10SndVel is set to zero.
4 Calculation error due to division by zero. AGA10SndVel is set to zero.