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Pairing 100A max clip-on current sensor CT with RaspIO 8 channel Analog->Dig converter


(George) #1

Hi guys

Looking at doing as much of this myself…

Thinking about pairing a 100A (as a main house feed) / phase #1 with a 8channel Analog->digital converter from RaspIO, being 8 channels I can then later add 7 more lower Ampage sensors for more circuits in the house.

Also want to use a Optical Utility Meter LED Pulse Sensor unit to count led flashes, 1Wh/flash.
The Optical Utility Meter LED Pulse Sensor it seems presents a RG45. whats the output on this from the unit? My Analog -> Digital takes a 0-1V input and outputs a similar digital reading.

Anyone with more electronic skills than me please check, compatibility…

Will then use Python and MySQL and Flask + Dash, or Plotly to graph usage.

G


Whats the output from : Optical Utility Meter LED Pulse Sensor
(Robert Wall) #2

You should follow the general design of the Arduino current sensor that is described in the ‘Learn’ section here. I do not know what the capabilities of your particular ADC are, but there are two important parameters, the input should be sensitive enough so that the c.t. you intend to use operates within its VA rating, and the sample rate should be high enough to give you at the very least two samples per cycle at the highest harmonic of mains frequency that you’re interested in. As a guide, the Atmel328P takes an input of around 1 V rms at maximum current (lower would be better), and runs at around 100 samples per cycle (5 k samples per second).

The optical pulse sensor from the shop actually has an overdriven analogue output - everything we know about it is either on the OEM Shop website or in ‘Resources’ here.


New emonSD release: emonSD-30Oct18 (Raspbian Stretch Pi3B+ compatible) :tada:
(George) #3

you write: “but there are two important parameters, the input should be sensitive enough so that the c.t. you intend to use operates within its VA rating”

so can a 0-100Amp sensor be accurate in a 0-10Amp circuit with the right burden resister configured?

G

so sorry, but my electronic understanding is not good, so following a general design section and I don’t understand what they saying is not helping, thus I ask questions until I understand. thought this was a help community and not a go read the docs…

G


(Robert Wall) #4

You should always choose a c.t. that is as close to, but larger than, the maximum you expect to measure. Every c.t. that has ever been made is inherently inaccurate at “low” current. The meaning of low depends largely on how much you pay for it. E.g. a “revenue” grade will be more accurate at lower current than a cheaper one of the same rating.

We were all there once, but no-one here is going to repeat what is already written up for you. If there is something specific that you don’t understand, please do ask. But most of us who are answering on these forums are doing it in our own time, just being helpful. We aren’t mind readers, so until you say exactly what you don’t understand, we can’t help.