Smart energy and metering
A meter sits on the wrong side of the surge protection, has to stay accurate for fifteen years, and must report its own death using energy it stored beforehand.
Evidence
What we can substantiate
Everything below is work we have actually done, described at a level that respects the client’s confidentiality. If you need detail, ask under NDA.
- Metrology accuracy held over temperature and years Class 1 accuracy is not hard to hit on a bench and is hard to hold across the operating range for a decade. Shunt tempco, reference drift, amplifier offset over temperature and self-heating all consume the budget. We write the budget down and design against it rather than calibrating at 25 °C and hoping.
- Isolation between metrology and communications The measurement side sits at mains potential; the comms side connects to an antenna or a service port a person can touch. The barrier has to be reinforced, sized for the working voltage and the pollution degree at the installation, and it must survive surge without the isolator becoming the weak point.
- Dying gasp sized against the real write time The last-gasp message needs energy for a detection delay, a radio transmit and a flash commit. We size hold-up against the longest realistic sequence including a worst-case flash program time, rather than against a typical figure that fails on the one unit that mattered.
- Surge survival where the protection is upstream of nothing A meter at the service entrance sees surges that installation protection downstream never encounters. Coordinated clamping, creepage sized for a polluted and possibly damp environment, and PCB geometry that will not flash over when the barrier is stressed.
- Hybrid RF and powerline, because neither works everywhere Powerline carrier reaches where RF is blocked by structure; RF reaches where the powerline is too noisy or the topology is wrong. A dual path turns a site visit into a retry — which matters when the asset is on a pole.
- Tamper detection that is not trivially defeated Magnetic, mechanical and reverse-flow detection, logged with a timestamp that survives power loss.
Common questions
Straight answers
Why RF and powerline together?
Because neither is reliable everywhere. Powerline carrier works where RF is blocked by building structure; RF works where the powerline is too noisy or the phase topology puts the concentrator on the wrong side of a transformer. A hybrid gives the deployment a fallback path, and that matters enormously when the asset is on a pole and a truck roll costs more than the meter.
What actually limits metering accuracy in the field?
Rarely the converter. Shunt temperature coefficient and self-heating come first — the shunt is dissipating power and its resistance moves with it. Then reference drift over years, then amplifier offset over temperature. A device calibrated at room temperature and deployed in an unheated cabinet in January is being asked to hold a specification nobody verified at that temperature. Write the error budget, and check it at both ends of the range.
How much hold-up energy does dying gasp actually need?
More than people budget, because the sequence is longer than it looks: detect the loss, decide it is real rather than a dip, wake the radio, transmit, then commit whatever has to be non-volatile. Flash program time on the worst-case block is often the dominant term, and it is specified as a maximum for a reason. Size against that maximum and the whole sequence, not against a typical figure.
Got a board to design — or one that won’t boot?
You talk to the engineer who would do the work. Reply within one business day, and we’ll sign your NDA before you go into detail.