Reference, Installation, and Operations Manual

Section 6: Meter operation

3-9000-743 Rev S

June 2013

 

 

 

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:

Table 6-2 AGA10 calculation status

AGA10SndVelStatus

Description
Value

 

 

 

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.

 

 

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).

Average weighted sound velocity

189