S-G-03–Specifications for the approval of type of gas meters, ancillary devices and associated measuring instruments
Revision number: 1
Supersedes: LMB-EG-08 and S-G-03
Part 13: Indicating devices
Table of contents
- 1.0 Scope
- 2.0 Metrological requirements
- 3.0 Technical requirements
- 4.0 Marking requirements
This part of the Specifications applies to indicating devices used with gas meters or ancillary devices submitted for approval. The indicating devices may be integral or non-integral mechanical, electro-mechanical or electronic.
2.0 Metrological requirements
The applicable requirements of Part 1, section 7.0 shall apply unless otherwise stated in this section.
2.1 Mechanical indicating devices
2.1.1 Mechanical indicating device gear ratios between all dials or drums shall be correct and in agreement with the intended values.
2.1.2 Proving and test provision (dial or drum) capacities, where present, shall be correct as marked on the faceplate of the mechanical indicating device.
2.1.3 The overall gear ratio of mechanical indicating devices from the input shaft to the lowest reading dial or drum shall be correct for use on the meter.
2.1.4 Mechanical indicating devices shall function as intended at any "other than reference" environmental conditions (gears shall mesh and shall not bind).
2.2 Electronic indicating devices
2.2.1 The following requirements shall be met at reference and "other than reference" environmental conditions:
- Electronic indicating device input parameters and displayed numerals shall be correct and in agreement with the intended values.
- The capacity of proving and test provisions, where present, shall be correct as marked.
- The operation and readability of electronic indicating devices shall not be affected by variations in temperature.
3.0 Technical requirements
In addition to the applicable requirements of Part 1, section 8.0, the following apply.
A cumulative, non-resettable indicating device, whether corrected or uncorrected, shall be so designed that the cumulative indication of the measurement units will not repeat when the host meter operates continuously at its rated or maximum capacity for a period of 90 days, unless stated otherwise in the subsequent sections of these specifications.
3.2.1 The indicating device face and markings thereon shall be of contrasting colours to provide for ease of reading.
18.104.22.168 All markings shall be indelible and shall not be adversely affected by environmental conditions.
22.214.171.124 The size of letters and numerals shall be such that they are clearly legible.
3.3 Mechanical indicating devices
3.3.1 Pointer type mechanical indicating devices
126.96.36.199 Pointer type mechanical indicating devices shall meet the following requirements:
- The minimum diameter of clock dial circles shall be 10 mm;
- Each dial shall be divided into 10 equal and clearly numbered divisions;
- The dial centres shall be located so as to avoid any possibility of ambiguity in reading;
- Each dial shall be marked to indicate the number of measured units per revolution of the pointer;
- The dials shall be distinctly separated from each other;
- The indicating device gearing shall be such that a complete revolution of any pointer shall cause the adjacent pointer on the left to advance one division;
- There shall be no overall multiplier indicated on the indicating device.
3.3.2 Drum type mechanical indicating devices
188.8.131.52 Drum type mechanical indicating devices shall meet the following requirements:
- The digits of the counter shall be in a straight horizontal line and easily visible through one or more cut-outs in the indicating device face;
- The arrangement of the counter drums and the cut-out(s) on the indicating device face shall be such that, with the exception of the fastest rotating drum, only one digit per drum is in full view at all times except when a drum is advancing from one position to another;
- The duration of this change period shall not exceed the time required for the fastest-rotating drum to make one-tenth of a revolution;
- Where the last digit shown on a drum type mechanical indicating device represents a multiple of applicable units of measurement, there shall be one of the following:
- A number of zeros marked on the indicating device face immediately to the right of the last digit, and in line with it, so that the reading of the indicating device with the additional zeros is in applicable units; or
- An inscription below the drum digits on the indicating device face to show the applicable multiplier, such as "Reading X l00 = m³". The multiplier shall be an integral power of 10.
3.3.3 Proving provisions for mechanical indicating devices
184.108.40.206 Mechanical indicating devices shall be equipped with one of the following to facilitate proving and testing:
- A proving dial;
- A proving drum that meets the following requirements:
- The proving drum shall be divided into 10 equal numbered divisions;
- The diameter of the proving drum in relation to the size of the cut-out in the register face shall be such that for any rotational position of the drum there is at least one numbered division in full view;
- There shall be a reference mark or marks designed in a manner to reduce or eliminate reading errors caused by parallax;
- The volume per revolution of the proving drum shall be marked on the face of the indicating device in the vicinity of the proving drum;
- The proving drum division markings and the size and location of the reference mark shall be such that the position of the drum with respect to the reference mark can be accurately determined;
- Where an indicating device is an integral component of a meter, the measured quantity per revolution of the proving drum shall be such that the proving drum makes at least one revolution every two minutes at Qmax.
- A proving dial and a test dial that meet the following requirements:
- They shall not be in the same geometric line as the reading dials;
- They shall have a minimum of 10 equally spaced divisions, each division shall have at least five equally spaced subdivisions and arrows shall show the direction of rotation of the pointers;
- The quantity per revolution of the associated pointer shall be clearly marked;
- No numbers shall appear on the divisions;
- Where an indicating device is an integral component of a meter, the measured quantity per revolution of the proving pointer shall be such that the proving pointer makes at least one revolution every two minutes at Qmax.
3.3.4 Gas meters with built-in correcting provisions
Where mechanical indicating devices are employed on meters with built-in correcting provisions, both the corrected and uncorrected indicating devices shall meet the requirement set out in 3.3.3(c), (ii).
3.4 Electronic indicating devices
3.4.1 The operation and readability of electronic indicating devices shall be suitable for use under the variety of environmental conditions which may be encountered in the intended operation, such as temperature, bright light, humidity, etc.
3.4.2 Where one electronic indicating device is used to indicate several different quantities, the following requirements shall be met:
- The quantity and the direction of bidirectional measurement shall be indicated;
- When not controlled by the operator, the minimum indication time shall be six seconds;
- The units associated with the registration and applicable multiplier, if other than unity, shall be indicated by use of one of the following:
- Abbreviations accepted by MC;
- A code (an explanation of the codes shall be available without the use of specialized equipment); or
- Other methods which clearly identify the units and applicable multiplier, without the use of specialized equipment.
3.4.3 Where an electronic indicating device is designed for use with a host meter which has no other indicating device conforming to the requirements of subsection 3.3.3, the electronic indicating device shall incorporate provisions for proving the meter with sufficient resolution so that the time required to conduct the test is no more than two minutes at Qmax.
4.0 Marking requirements
The applicable requirements of Part 1, section 9.0 shall apply unless otherwise stated in this section.
4.1 Indicating devices forming an integral part of a meter shall be exempt from the requirements set out in Part 1, section 9.0.
4.2 Indicating devices which are an integral component of the host meter shall bear an indelible marking of the manufacturer's part number, which shall be unique for each model of indicating device. Where only one model and version is available, the device is exempt from this requirement.
4.3 Where an indicating device is not intended to display more than one quantity, the units or symbol being indicated shall be prominently marked or indicated on or adjacent to the indicating device face.
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