Within the UK the second version of the Smart Metering Equipment Technical Specifications (SMETS) has been published and countries around the world are consulting on and publishing their own recommendations for communication and usability standards for smart metering systems. Although these standards specify particular communication protocols, there is still flexibility to allow engineers to use the best protocol for the job. This can however leave buyers frustrated, with diminishing economies of scale reducing their buying power.

Our summary of the SMETS implications below includes tips on how to go about choosing frequency products for your smart meter design. Alternatively you can use the side navigation to  skip straight to our range of recommended products including tips on maximising buying power and achieving ultra-low power consumption when designing your device.

Smart Meter System outline

In essence the standard smart metering system or smart grid is composed of one or more smart meters which have the ability to communicate with an in-home hub and a neighbourhood hub, which in turn communicates with a receiver being monitored by a utility company.

Smart meters are composed of three major blocks of circuits which may be integrated into a SoC or incorporated into the device as separate modules. The purposes of these modules are:

  • Measurement
  • Communication
  • User interaction
Golledge Electronics can provide components for various smart metering applications.

Measurement

Measurement is the primary role of a smart meter. Ultimately these devices are created to measure the usage of gas, electric, water or help with temperature control. Various means of measurement are used dependant on the type of fluid being monitored. Viscous fluids may be measured using flow meters, gases may require pressure monitoring, and electricity may be monitored using single, twin or polyphaser metering.

Time-keeping

All smart meters, regardless of the utility they are measuring, require accurate time-keeping in order to allow accurate data analysis and billing. Most importantly time synchronization also ensures reliable transmission of data to the neighbourhood hub and utility receiver in the wide area network as discussed below.

“The most recent version of SMETS states that the clock within all types of smart metering equipment must be accurate to within 10 seconds of UTC date and time.”

Not only is it important for smart meters to achieve accurate time synchronization, but they must also do so using only a tiny amount of power. Most gas and water meters will be required to maintain power for extended periods of time, reliant solely on battery power. This means every nanoamp of extra power consumption counts and it’s important to specify the lowest energy-consuming peripheral products possible for pairing with communication and measurement chipsets or smart meter SoCs.

What does this mean for frequency components?

In practice the requirements of smart meters mean additional specifications standards are required for frequency components: An operating temperature range of -25 to +55°C with a storage temperature range of -30 to +60°C is common within the industry, with ±10ppm stability over the operating temperature range being preferred to ensure radio frequency accuracy.

Ageing is also paramount: ±10ppm over 20 years is the widely accepted figure for ageing of frequency components within the smart metering industry.

Communication

Many types of communication protocol are common within smart metering systems including short range wireless standards for home or building networks, such as ZigBee and BLE (Bluetooth low energy). Neighbourhood area networks also make use of 2.4GHz ZigBee and BLE but also commonly use sub 1GHz communications. Finally WAN (wide area networks) may use GSM and 3G or Ethernet and fibre.

SMETS standard stipulates the use of ZigBee in some types of smart meter systems (see below) but for others engineers are free to find a novel solution.

Measurement

These short-range networks within a smart meter system allow communication between the smart meter, in-home display (or "home-hub") and smart appliances within the building or home.

This type of communication between the meter, appliances and the home or building hub means the user can see a full picture of their energy usage, including a breakdown of that usage by appliance, great for monitoring peak time activity and energy budget expenditure. Some smart appliances and hub communications also allow for on/off signalling so an appliance can be controlled directly from the home hub.

For both Gas and Electric Smart Metering Equipment (GSME or ESME) the SMETS standard stipulates:

“The HAN Interface of GSME [or ESME] shall be capable of joining a ZigBee SEP v1.2 Smart Metering Home Area Network which: …operates within the 2400 – 2483.5 MHz harmonised frequency band”

SMETS

Both electric and gas metering equipment must also be "certified by the ZigBee Alliance as compliant"

The In-Home Display device used within the HAN must also meet both of these functionality requirements.

There are also auxiliary devices which may be included in the HAN section of a smart metering system, including prepayment interface devices and connected auxiliary load control switches.

In addition to the above requirements all smart meters must be registered and conform to DLMS (Device Language Message Specification) standards. DLMS have a conformance checking tool which you can find here.

WAN - Wide Area Network

In order to transmit data to a utility company the smart meter will then transfer data through a secure data network outside of the home, usually known as the wide area network.

WANs may consist of data transmission directly to the utility receiver, or depending on the density of meters and level of network coverage within an area, data may first be aggregated at a neighbourhood hub or data aggregation point (DAP) using ZigBee communication. This data is then parcelled into secure data packets and transferred using the WAN communication protocol.

Wide area network communication does not require the fast data rate necessary within HANs but must instead ensure the signal can be carried greater distances than those within the HAN. Protocols common to this level of network include Cellular GSM, LoRa, 3G technology and even Ethernet and fibre.

Lower data transfer rates are typically employed and available channels can be significantly narrower, requiring the use of smaller bandwidths.

 

Recommended frequency products for Smart metering systems

Get the lowest-power consumption for your smart metering device using our ultra-low power, industry standard footprint, low cost products listed here.

Can’t find quite the right frequency or specification? Golledge have a range of over 20,000 product lines so drop us an email at sales@golledge.com and one of our knowledgeable sales engineers will be in touch to help.

 

Ultra-low power crystals are the mainstay frequency provider for smart metering systems


32.768kHz crystal solutions for smart metering projects

Golledge recommend the following three 32.768kHz crystals for use within smart metering projects. In particular:

  • CM7V-T1A is available with a 6pF option help achieve low current consumption
  • The most popular option for the GSX-315, 12.5pF, is perfect for pairing with the majority of industry chips
  • Although older technology, the GSX-200 offers a low-cost option for boards which can absorb the extra board space required for this component

You can access more information on each of these 32.768kHz crystals below:

32.768kHz crystal options for Smart metering

CM7V-T1A

SM 32.768kHz Watch Crystal with Military Temperature Range


The CM7V-T1A surface mount watch crystal offers high shock and vibration resistance within a minature ceramic package with metal lid. Optional automotive and military operating temparture ranges means this 32.768kHz crystal is available for a wide range of applications. 

  • 32.768kHz
  • Miniature ceramic package with metal lid
  • High shock & vibration resistance
  • Extended temperature range options
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GSX-315

Miniature SM 32.768kHz Watch Crystal


Our most popular 32.768kHz solution, the GSX-315 offers highly competitive pricing and low power consumption (just 0.1uW typical) in a miniature vacuum sealed ceramic package.

  • 32.768kHz
  • Miniature ceramic package with metal lid
  • Vacuum seal for excellent long-term stability
  • Low cost for volume applications
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GSX-200

32.768kHz CM200C Watch Crystal


The plastic moulded surface mount package of the GSX-200 is a fully compatible drop in replacement for MC-306, DMX-26S, FSRLF, E1WS, SMQ32SL, RSM200S and other industrial standard plastic-package crystals. The ideal part for use within existing designs where a footprint has already been decided, the GSX-200 offers highly competitive pricing and is available up to industrial operating temperature ranges.

  • 32.768kHz
  • Low profile plastic moulded package
  • Miniature size for high density applications
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12.0MHz timing solutions for smart metering

For boards that call for a 12.0MHz crystal timing solution, the GSX49-4 provides the lowest cost solution, whereas the GSX-331 features superb aging (±1ppm in the first year for many options) and has a small 3225 form-factor package to allow for more board space during the design stage.

12.0MHz crystal solutions

GSX-331

3.2 x 2.5mm High Frequency SM Crystal with Tight Specifications


The GSX-331 miniature surface mount crystal is available over wide available frequency range from 10.0 ~ 125MHz. GSX-331 features a miniature package measuring 3.2 x 2.5 x 0.8mm, and is available in a choice of operating temperature ranges and with a range of temperature stabilities. Find more information and configure your product here.

  • 10.0 ~ 125MHz
  • Metal lid can be grounded to minimise EMI
  • Seam sealed for excellent stability
  • Tight specifications available
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GSX49-4

4.3mm Low Profile SM Crystal


The highly configurable, low profile GSX49-4 crystal is available at frequencies between 3.18 ~ 90.0MHz and features a range of calibration tolerance, temperature stability, operating temperature range, and circuit condition options. One of our most competitive crystals, you can find full product specifications and configure your product here.

  • 3.18 ~ 90.0MHz
  • Industry standard HC49 footprint
  • Low profile case
  • Fundamental mode available up to 50.0MHz
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24.0MHz and 26.0MHz frequency solutions for smart metering

Some of the communication protocols used within smart meters call for 24.0MHz and 26.0MHz frequency products. For meeting these frequency requirements we recommend the GSX-331 (with max. aging of ±1ppm first year for most options) and the GSX-333 (with max. aging of ±2ppm in the first year for most options)

24.0MHz and 26.0mhZ crystal solutions for smart metering

GSX-333

3.0 x 2.5mm High Frequency SM Crystal with Tight Specifications


The GSX-333 is available at high frequencies from 12.0 ~ 125MHz and features a miniature package measuring 3.2 x 2.5 x 0.7mm. This miniature SM crystal is available in a choice of operating temperature ranges, temperature stabilities and calibration tolerances. Find more information and configure your product here.

  • 12.0 ~ 125MHz
  • Metal lid can be grounded to minimise EMI
  • Seam sealed for excellent long-term stability
  • Ultra-miniature for maximum space saving
VIEW PRODUCT

GSX-331

3.2 x 2.5mm High Frequency SM Crystal with Tight Specifications


The GSX-331 miniature surface mount crystal is available over wide available frequency range from 10.0 ~ 125MHz. GSX-331 features a miniature package measuring 3.2 x 2.5 x 0.8mm, and is available in a choice of operating temperature ranges and with a range of temperature stabilities. Find more information and configure your product here.

  • 10.0 ~ 125MHz
  • Metal lid can be grounded to minimise EMI
  • Seam sealed for excellent stability
  • Tight specifications available
VIEW PRODUCT


30.0MHz and 32.0MHz crystal timing solutions for smart metering projects

Finally for projects which require 30.0MHz or 32.0MHz options we would recommend the GSX49-4 for projects where cost is paramount, and the GSX-331 for projects where aging is paramount. Don't forget our expert team will be happy to help answer any queries you have on using crsytals within your metering project. You can contact a team member here.

30.0MHz and 32.0MHz crystals for metering solutions

GSX49-4

4.3mm Low Profile SM Crystal


The highly configurable, low profile GSX49-4 crystal is available at frequencies between 3.18 ~ 90.0MHz and features a range of calibration tolerance, temperature stability, operating temperature range, and circuit condition options. One of our most competitive crystals, you can find full product specifications and configure your product here.

  • 3.18 ~ 90.0MHz
  • Industry standard HC49 footprint
  • Low profile case
  • Fundamental mode available up to 50.0MHz
VIEW PRODUCT

GSX-331

3.2 x 2.5mm High Frequency SM Crystal with Tight Specifications


The GSX-331 miniature surface mount crystal is available over wide available frequency range from 10.0 ~ 125MHz. GSX-331 features a miniature package measuring 3.2 x 2.5 x 0.8mm, and is available in a choice of operating temperature ranges and with a range of temperature stabilities. Find more information and configure your product here.

  • 10.0 ~ 125MHz
  • Metal lid can be grounded to minimise EMI
  • Seam sealed for excellent stability
  • Tight specifications available
VIEW PRODUCT


TCXOs for smart metering applications

Temperature compensated oscillators allow for extreme accuracy over a wide range of temperatures, perfect for smart meters that require time accuracy whilst withstanding extreme weathers

Both of our smart-recommended TCXOs feature aging of ±1ppm as maximum within the first year as standard, and both feature superb temperature stability options. The GTXO-93T usually represents the lowest cost option, whereas the GTXO-253 minimizes board space with a tiny 2520 form-factor package.

TCXOs recommended for Smart Meter designs

GTXO-253T

1.8V ~ 3.6V Ultra-tight Stability TCXO for GPS


The GTXO-253T temperature compensated oscillator is entirely suited for GPS applications, featuring frequency stability as tight as ±0.5ppm, fast start up time of 3ms maximum, and a miniature 2.5 x 2.0mm package.

  • 10.0 ~ 52.0MHz
  • Ideally suited for GPS applications
  • ±0.5ppm frequency stability option
  • Supply voltage from 1.8V ~ 3.6V
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GTXO-93T

1.8V ~ 3.6V SM TCXO for GPS


Ideal for GPS applications the GTXO-93T TCXO features analogue compensation, ensuring smooth output at variable temperatures. This miniature 3.2 x 2.5mm footprint component also features exceptional stability performance, with options as good as ±0.5ppm and power consumption as low as 1.5mA.

  • 10.0 ~ 52.0MHz
  • Analogue compensation - no steps
  • Ideally suited for GPS applications
  • Supply voltage from 1.8V ~ 3.6V
VIEW PRODUCT

 

SAW Filters for metering applications

SAW filters provide refined filtering, essential for smart metering systems

In particular TA0223A is perfect of filtering the 2.4GHz ZigBee band, ideal for use with meters utilizing this type of technology. Speak to our team today for more filtering options or for more details.

SAW filters recommended for Smart metering designs
3.0 x 3.0 x 1.4mm

GSRF TA1404A

869MHz RF SAW Filter with 2MHz bandwidth


The ultra-miniature 3.0x3.0mm package of the TA1404A SAW filter makes this product ideal for size-sensitive applications, and insertion loss of only 3.0 dB means you can be assured of a strong in-band signal.
  • 869MHz
  • Narrow 2MHz bandwidth
  • Low insertion loss of 3.0dB
  • Ultra-miniature package
DOWNLOAD PDF
3.0 x 3.0 x 1.4mm

GSRF TA0223A

2441.8MHz RF SAW Filter with 83.5MHz bandwidth


The ultra-miniature 3.0x3.0mm package of the TA0223A SAW filter makes this product ideal for applications where product-size is paramount.
  • 2.4418GHz
  • 83.5MHz bandwidth
  • Insertion loss of 5.0dB
  • Ultra-miniature package
DOWNLOAD PDF

 

Smart metering applications which require Real Time Clock Modules (RTCs)

RTC modules offer extra functionality and lower power consumption than a standard SoC solution

For metering applications which are required to withstand temperature fluctuations, the RV8803C7 RTC with temperature compensation and current consumption of only 240nA is a good option. Alternatively if power consumption is the determining factor in a design, the RV1805C3 consumes just 17nA in standby mode and is a popular option for meters which cannot easily access a power supply.

RTC modules recommended for Smart metering designs

RV8803C7

RTC I2C bus High Accuracy


A highly accurate RTC module with I2C bus interface providing timing accuracy of ±3ppm (or ±1.81 seconds per day), the RV8803C7 is also the world's smallest RTC module, with a package footprint of only 3.5 x 1.5mm. In addition to providing excellent frequency stability this real time clock module is also one of the lowest power temperature compensated RTC modules in the world with back up power requirement of only 240nA with automotive grade options available.

  • 1.0Hz ~ 32.768kHz
  • Temperature compensated
  • Ultra-low Power
  • I2C-Bus
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RV1805C3

RTC I2C Bus Low Power


With ultra-low current consumption of only 17nA the RV1805C3 boasts the lowest power consumption of our entire range of real time clock modules. This RTC with miniature 3.7 x 2.5mm package and I2C bus interface offers excellent stability for an uncompensated part and incorporates many additional functions including alarm, timer, interupt, power management and trickle charge.

  • 1.0Hz ~ 32.768kHz
  • Extremely low current consumption
  • Miniature package with integrated crystal
  • Trickle charger, power management & switch
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