2. Architecture of a smart gas meter with wM-Bus
The main buildings blocks in a smart meter fully based on electronic components include:
• sensor(s) for the metrology part
• ultra-low-power MCU to process the sensor data and calculate the consumption
• communications system
• a power supply system
In today’s gas meters, the sensing portion (Figure 4
) reports the flow throughput (often thru a Reed switch) along with exact gas pressure and temperature measurements. The main MCU block processes the sensor data and adjusts the gas flow volume to a normalized quantity, which is required for customer billing.
Normally, there is also a motor valve that can also be controlled remotely (e.g. over the wM-Bus link) and in some countries a pre-payment option is required as well.
Click on image to enlarge.
Figure 4: Smart Gas meter (wM-Bus as a Sub-1GHz RF link at 169MHz or 868MHz)
Click on image to enlarge
For water and heat meters, the most common sensors used today are detecting the flow thru measuring rotation speed and direction.
A heat meter is a water meter with additional precision temperature measurements for capturing the temperature of forward and backward flow. Adding an RF subsystem (such as a sub-1GHz or 2.4GHz communications module) is the way to make heat and water meters “smart”.
It’s important to remember that water, heat and gas meters are all powered thru batteries, meaning ultra-low-power consumption is a major consideration. Since these three types of meters have a limited space for the battery, a dedicated power solution for optimizing battery life becomes mandatory.