[RE-wrenches] Data System Puzzle

[vince at solarenergydesign.com]

There is no other wiring close to the sensors. There is likely some radio
frequency interference on site because my client uses a radio transmitting
system for his internet and phone connection. Can Hall Effect Sensors be
effected by RF?

> Do you have any wiring close to the actual sensors or circuit board that
> might be interfering with them?
>
> -----Original Message-----
> From: vince at solarenergydesign.com
> Sent: Thursday, February 03, 2011 11:46 AM
> To: RE-wrenches
> Subject: [RE-wrenches] Data System Puzzle
>
> Sorry for the long post. I don't know how else to communicate this issue.
> We installed an Energy Recommerce data system on a project last year that
> we have not been able get working properly. Everything works except the
> monitoring of the series string amperage outputs from the solar array.
> There are 3 pv source circuit combiner boxes with 11 series strings of 14
> modules and 1 with 10 series strings of 14. Each combiner box feeds one
> inverter with its own conduit run. The data system shows amperage from
> each circuit consistent within each combiner box, typically with a range
> of variance of about 1.5 amps DC between series strings.  Each combiner
> box will show totally divergent amperages. For example, combiner box 1
> might read 2 amps, combiner box 3 reads 10 amps, and at the same time our
> clamp meters are reading the actual amperage at around 5 amps consistently
> between every box for every circuit. The same combiner boxes will
> consistently read either too low or too high. The problem may be in the
> interface between the Hall Effect sensors that the circuit board in the
> combiner box uses to measure the DC current. The Hall Effect sensors
> deliver a calibrated voltage based on the strength of the magnetic field
> around the series string circuit as it goes through the box. The combiner
> box then calculates the amperage based on the millivolts that the Hall
> Effect sensor produces. For example 500 millivolts equals 5 amps.  The DC
> output voltage of the Hall Effect sensor varies by about 50 millivolts or
> more, so rapidly that it’s hard for our meters to follow it. We have
> spent
> countless hours on the phone with Energy Recommerce technicians trying
> everything that anyone could think of to trouble shoot the problem. Their
> system uses a MODBUS protocol for transferring the data and there seems to
> be no problem with the data transmission or connectivity.  I would love to
> hear from anyone that sees a pattern to this problem that might help us
> find a solution.
>
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