S-G-03–Specifications for the approval of type of gas metering devices–Part 7

Category: Gas
Issue date:
Effective date:
Revision number: 3
Supersedes: S-G-03 (rev. 2)


Part 7: Ultrasonic gas meters

Table of contents


1.0 Scope

This part of the Specifications applies to ultrasonic gas meters which operate by determining the difference in transit times of bursts of ultrasonic energy travelling in the upstream and downstream direction.

2.0 Unit requirements

Note: The following requirements of Part 1, section 1.0 apply:

  • 1.1 Use of units
  • 1.2 Metric units of measure
  • 1.3 Display of units of measure for non-trade purposes

3.0 Metrological requirements

Notes: The following requirements of Part 1, section 2.0 apply:

  • 2.1 Rated operating conditions
  • 2.2 Flow rate characteristics
  • 2.3 Maximum permissible errors
  • 2.6 Working pressure
  • 2.7 Temperature
  • 2.8 Durability
  • 2.9 Vibrations and shocks
  • 2.11 Flow direction
  • 2.12 Flow disturbance
  • 2.16 Supply voltage variation

According to the characteristics of the meter, the following requirements may also apply:

  • 2.14 Different gases
  • 2.15 Influences from ancillary devices

3.1 Maximum permissible errors

The error of the volume registration must not exceed the following maximum permissible errors (MPE) indicated in Table 1 below.

Part 7, Table 1: Maximum permissible errors for ultrasonic gas meters
Meter type Test conditions Registration type MPE
Ultrasonic gas meter Footnote 1 Reference or "other than reference" Unconverted volume ± 1.0%
Ultrasonic domestic gas meter Reference
or "Other than reference" with ambient temperature within ± 5°C of the working temperature
Unconverted volume ± 1.0%
"Other than reference" Converted volume ± 2.0%

3.2 Weighted mean error

The weighted mean error (WME) must not exceed the tolerances indicated in Table 2 below.

Part 7, Table 2: Weighted mean error for ultrasonic gas meters
Flow rate (Q) Ultrasonic gas meters Ultrasonic domestic gas meters
QminQQmax ± 0.3% of reading ± 0.5% of reading

Note: The tolerances apply after any corrections performed within the meter itself but prior to the application of linearization algorithms by equipment auxiliary to the meter.

3.3 Repeatability

The repeatability error must not exceed the tolerances indicated in Table 3 below.

Part 7, Table 3: Ultrasonic meter repeatability
Flow rate (Q) Ultrasonic gas meters Ultrasonic domestic gas meters
QminQQmax ± 0.2% of reading ± 0.4% of reading

3.4 Component exchange

The meter's performance as a result of any component exchange (i.e. the exchange of one circuit board, one transducer or one set of transducers) must not change by more than ± 0.2% and in no case must exceed the MPE specified in subsection 3.1.

4.0 Technical requirements

Notes: The following requirements of Part 1, section 3.0 apply:

  • 3.1 Design, composition and construction
  • 3.4 Case
  • 3.5 Zero flow
  • 3.6 Flow direction
  • 3.7 Indication
  • 3.8 Output
  • 3.9 Power sources
  • 3.10 Software
  • 3.12 Registration

According to the characteristics of the meter, the following requirements may also apply:

  • 3.2 Minimum temperature range
  • 3.3 Automatic volume conversion
  • 3.11 Compressibility factor

4.1 Interior finish

The interior finish of the meter must not exceed a relative roughness of 0.0000625.

4.2 Pressure tap

A pressure tap must be located on the meter body.

Note: This requirement does not apply to meters with a Pmax of 10 psig or less.

4.3 Outputs

The meter must provide one or more outputs proportional to the volume of gas, expressed at line conditions of pressure and temperature, which has passed through it.

Note: This requirement does not apply to ultrasonic domestic gas meters.

For bidirectional applications, a separate volume output must be provided for each direction.

4.4 Speed of sound

Multipath meters must be capable of indicating the speed of sound in gas for each path.

4.5 Transducer malfunction

The malfunction of any transducer pair in a multipath meter must not cause the meter to cease functioning but must cause an alarm to be generated.

4.6 Communications

The meter must use the standard communication protocol set out in:

  • ANSI C12.18-1996; and
  • IEEE P1377/ANSI C12.19-1996

Alternately, the manufacturer must provide, free of charge, software to interrogate, control and verify the meter, subject to the following conditions:

  • The executable software must be formatted for personal computers.
  • Operating manuals and documentation must also be provided.
  • The software must preclude the possibility of disruption of the meter's operation during the verification process.

    Note: MC will ensure that the software is used solely for the purpose of the inspection of meters by government inspectors and will not disclose the contents of the software or its documentation to third parties.

4.7 Low flow cut-off

The meter must accumulate zero volume at flow rates of less than 0.5% of Qmax.

5.0 Marking requirements

Notes: The following requirements of Part 1, section 4.0 apply:

  • 4.1 Permanency and legibility
  • 4.2
    • (a) Departmental approval number;
    • (b) Manufacturer's name or registered trademark;
    • (c) Model or type designation;
    • (d) Serial number (on the meter body) or meter serial number if different;
    • (f) Pmin (where applicable) and Pmax;
    • (g) Qmax;
    • (h) Qmin;
  • 4.10 Software;
  • 4.12 Inspection number;
  • 4.13 Verification marks;

According to the characteristics of the meter, the following requirements may also apply:

  • 4.3 Bar codes or quick response codes;
  • 4.4 Temperature converted volume;
  • 4.5 Pressure converted volume;
  • 4.6 Unidirectional flow measurement (for domestic ultrasonic meters; the inlet connection);
  • 4.7 Bidirectional flow measurement;
  • 4.9 External power supply;
  • 4.11 Connection terminals
  • 4.14 Operating information
  • 4.15 Ancillary devices

5.1 Inside meter diameter

The inside meter diameter must be marked on the casing or on a nameplate permanently affixed to the meter in such a way to be easily readable when installed.

Note: This requirement is not applicable to ultrasonic domestic gas meters.

5.2 Additional markings

The following information must be indelibly marked on, or be capable of being displayed by, the meter:

  • Final meter factor, where used;
  • Zero offset, where used;
  • Density, where used;
  • Viscosity, where used;
  • Delay times for transducers, where used;
  • Any other user-programmable factors used;

5.3 Component exchange

5.3.1 Transducers

The following information must be marked for meters with transducers which can be exchanged at the meter's operational location:

  • Transducer model number (on each transducer);
  • Transducer serial number (on each transducer);
  • Pressure range of transducers (on each transducer);
  • Identification of each transducer port (on the meter body).
5.3.2 Electronics

The following information must be provided for meters with circuit boards which can be exchanged at the meter's operational location:

  • Circuit board model number;
  • Circuit board serial number.

5.4 Remote component parts

Where portions of the meter are intended to be installed remotely from each other in a multi-meter installation, the component parts must bear sufficient additional markings as are necessary to clearly identify which components of the system will operate with each other.

6.0 Sealing requirements

Note: The requirements of Part 1, section 5.0 apply, except subsection 5.4.

6.1 Transducers

Where a manufacturer cannot demonstrate through test results that transducers can be exchanged without requiring reprogramming of the processing circuitry and without affecting the meter performance, individual transducers must have suitable provisions for sealing them to the meter body.

6.2 Electronics

The processing circuitry must have suitable provisions for sealing circuit boards to the meter body. Where access is not otherwise prevented by the conventional sealing method, as per S-EG-02, the electronics package may require a jumper to prevent unauthorized changing of calibration parameters.

7.0 Administrative requirements

Note: The requirements of Part 1, section 6.0 apply.

8.0 Performance test requirements

Note: Test conditions and performance tests can be obtained by contacting MC.