Smart meter sizes - SMETS1 and SMETS2

  • 19 March 2018
  • 26 replies

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26 replies

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Good question @gingertips 

Mains gas passes through your meter at very low pressure - the equivalent pressure to that imparted by a 250mm high column of water.

We also have domestic devices which use very small volumes of that gas. The gas meter must be capable of registering the amount used by a pilot-light, for example.

Using a rotating device like a propeller/turbine in the gas flow is not going to be very accurate. The force required to move the blades in the gas flow is pretty high, and the bearings deteriorate over time.

The well-established method is to use a system of four diaphragms. This provides an accurate measurement based on volume, whilst remaining unaffected by particles of dust in the flow. The standard gas meter size is dictated by the four volumetric chambers inside it.

Landis & Gyr use reflections of ultrasonic pulses to detect gas flow. The return-pulse is slightly delayed if the gas is flowing.

There’s a more detailed technical explanation of ultrasonic flow measurement here on an external website.

There is also a list of the currently-approved Smart Meters here on the SmartMe site. This shows that Landis & Gyr have one approved SMETS2 gas meter, the G470-672



The 470-672 is fitted by British Gas. I’m not aware of any other Energy Supplier who uses them.