Sub-Metering Made Easy

The system developer wanted to design a digital solution where a PCB based hardware device would calculate energy usage in various sub-panels and circuits without any electrical re-wiring becoming necessary. The development team knew that current transformers could be installed on existing wiring to get readings, which could be utilized to calculate the energy usage. They used Akida’s TARAS cards, which easily plugged into their PCB design with standard pin connectors and its diminutive 1.5 inch square template meant that the final PCB was a manageable size that fit into a standard weatherproof panel. Current transformers are attached to appropriate wiring in the existing electrical panels and connected with low voltage cabling to the new sub-metering hardware device. The readings from the current transformers are transmitted to the TARAS cards via the PCB. When the system’s software needs real time information, the TARAS cards are interrogated through the PCB in order to receive energy data calculated from the coil readings. Since the data packets use a standardized protocol and are in ASCII format, the PCB can feed them directly into the system software (without any further software coding to interpret the readings). There was no impact to the choice of communication method for the system since the energy metering was an “on-board” component of the PCB allowing the developer team to build in the communication platform of their choice elsewhere on the PCB to relay the data to the end-use point.

The developer team saved at least a year of engineering time needed to design hardware to perform the digital energy metering with such a small footprint. The final cost of the TARAS cards purchased in large volumes becomes a nominal component cost similar to communication modules and memory cards so the net effect on the end product cost was negligible. A compact sub-metering panel that can be installed without any building re-wiring gives the system developer’s customers a definitive edge in the competition for real estate management. The TARAS card’s standardized communication protocol provided the added advantage where all the devices based on the card could communicate easily with each other to create systems with flexible configuration that can even be used in campus settings.

The TARAS card’s ability to offer digital energy metering in a plug-in card allows energy metering hardware to be developed quickly reducing development cost as well as manufacturing cost. Even though the TARAS card is not certified for revenue metering for utility use it meets accuracy standards that allow its use for cost sharing systems.