Renewable Energy Monitor

Thoughts on processing the Senis/Ametes 200 Amp Bus Bar current sensor output to report to the Nagios Renewable Energy Monitor.

The Senis/Ametes BBMXX-kit-1 kit is a step up into the world of industrial sensors. It can measure up to 200A along a chunky bus bar bored at each end with 8mm connector holes.

It uses two sensors arranged around the bus bar so their outputs cancel noise. It squirts the measured current as a voltage difference between the two sensors that appears as up to a 4V difference on the unit's two output wires.

I processed the output through an LM324 instrumentation amplifier to present a high impedance to the sensor's output - a decision made on a “it couldn't hurt” basis. More importantly perhaps the instrumentation amplifier boosts the BBMXX's output by 20% to extend its 0-4V output range to the full 0-5V input range that the Arduino makes available.

Here's how that all looks:

We have the BBMXX at top right, with its dual output and 0-5V power supply connected by its supplied RJ-11 plug to a standard phone pattress, then via coiled length of four-core phone cable to the inputs of the instrumentation amplifier.

The output is being fed into one of the analogue ports of a chibiArduino. Nothing special about that choice - just a spare Arduino I happened to have available. The chibi is running the Arduino code that re-formats the 0-5V input voltage to the real voltage it represents and squirts it across the network to the Nagios Renewable Energy Monitor.

All powered up in the photograph above, the BBMXX's output with no current flowing through the bus bar reads 0.01%.

BBMXX-1-Kit v AttoPilot Current and Voltage Sensor