Data Collection Technologies
There are a number of different terms that are used in aM&T system when describing how data is collected:
- Devices = The metering hardware that is needed (Meters | Loggers | Modems | Gateways)
- Device Protocols = How the metering hardware device “talks” to other parts of the aM&T system (Modbus | M-bus | Pulses | Proprietary)
- Device Connectivity = The way the hardware sends information around a site over shorted distances (Wired | Wireless)
- Network Connectivity = The way the hardware sends information across larger distances to monitoring software for example (IP | GSM | future LoRa)
Once the data has moved from the devices, via the protocols and down the wire or over the air the data comes out to your software either in the cloud or locally. The data journey can be somewhat confusing considering the amount of technology and steps that must employed throughout. However, there is always a solution for each scenario and the true skill is to utilise the correct result for each appropriate case, in order to implement the key design principles.
Quite often the site topography is a main driver of system cost when selecting the data collection technology to use:
- Understanding site topography is critical for the design of a successful device connectivity and back haul solution
- Site health and safety working restrictions must be considered in the design
- Connections to tariff meters can be difficult and may need certified connections from the Supplier or Meter Operator
- There can be other end users expectations that must be considered
Data acquisition at different site types
Generally within an office block you will have riser cupboards allowing you to work vertically up and down the building. Landlord supplies, tenant supplies, a lot of meters can also be present but it can be quite an easy installation utilising hard wiring, keeping costs relatively low.
Campus Style sites – e.g a University
This type of site generally has a dispersed estate over a large area with a combination of high and low-rise buildings. In this situation you need a whole variety of technologies – wired, radio, IP, perhaps making this style of site the most complex to design and implement.
Factories – Split sites
Here you can find harsh environments, noise, switch-gear and machinery. This increases the number of health and safety issues to be aware of. Understanding what is happening in that site may determine the technology employed.
Simple from a metering point of view, but from a data connectivity perspective to get to back haul can be quite complex and challenging as distances maybe large.
Understanding the various, different types, colours and size of meters including gas, oil and electricity already present on site is vital. It is useful to be able to account for what parameters are being measured and the communication standards that are currently being used such as ModBus etc. Thereby, accomplishing the aim of standardising across sites as previously described.
It is important that it has local memory and that it can communicate. Generally data loggers are where you come across proprietary protocols and if you take a view of the whole system, that area is where you may need to replace part of the system. As long as you have data loggers that have local memory and can push the data to where you need it then you have made a good decision.
Battery powered devices are reliable but consider their lifetime, how they will be maintained once installed and the management that will be needed?
Typically if you can use a LAN or access an existing WiFi network, you can send data much faster as this is always available. This can be especially useful if you begin to look at demand response and other newer technologies and there is a requirement to get closer to real-time (or near-time) data.
A University for example will have a Local Area Network (LAN) running around the campus. It is an important consideration is that when the site already has a high capacity dedicated network, it’s a clever idea to use it if you can.
The amount of traffic that a metering system will add is negligible, although it’s not always that simple. You can have resistance from the IT staff who look after the network, who may be reluctant to allow data which they do not control to pass over it. Where it is available, do use it or at least pursue the conversation as it will deliver a very reliable, high quality, data acquisition system for not a lot of money. It certainly helps in this instance to consider the standards being employed to make the case for access.
Using mobile GSM/SMS networks is also very common and can be used to isolate aM&T data from any existing network, but consider the costs, configuration and management of any solution using this.