What is the difference between using a chip like the ATM90E32AS used in the circuitsetup vs the MCP3208 the iotawatt uses?
Is one more accurate than the other? Are they both able to measure the same things (reactive power, power factor, etc)?
The ATM is a dedicated energy meter chip. It’s designed to do revenue grade metering for up to three voltage and three current sensors. I’m sure it works very well and it is reasonably priced. They represent accuracy at 0.2% which is great and probably what’s necessary for a very accurate energy meter. The chip measures all six of it’s inputs continuously.
The MCP3208’s that IoTaWatt uses are also very accurate, but at a more basic level. The difference between the two technologies is that IoTRaWatt samples each input periodically.
Each ATM chip can monitor up to three circuits, so it would take 5 ATM chips to do what IoTaWatt does with 2 MCP3208. But the ATM chips can work asynchronously, freeing the main processor from dedicated SPI ADC sampling.
Stepping back, this is a recurring theme, where hardware oriented folks fixate on the hardware capabilities rather than results. If you separate out the data collection activities from the data reporting capabilities, I think IoTaWatt starts to distinguish itself. It would be relatively easy to change the data collection in IoTaWatt to use chips like the ATM. There are some issues, like replicating the any-to-any phase correction capabilities of the MCP3208 collection, but it can be done without any impact at all on the datalogging and reporting functions - except maybe a positive effect of making more processor time available to do it.
If all you want to do is shovel real-time data to the cloud and then play with the bubbles on your phone, I’d probably go with a simple energy chip system. IoTaWatt stores years of high resolution data and makes it available through a web-server in seconds. It can upload data seamlessly to one or many external databases. That’s the real differentiator between it and other monitors.
I believe yopu could get more accurate results from the energy chip model. That said, do you care if you are going 60mph or 60.2935 mph? What is accurate enough for you?
Yes, they both can measure all of those things.
I have to agree with @overeasy here. You really need to be clear on what you want to do and how accurate the measurements need to be to achieve your goals. I still have a strip of energy measuring chips in my parts box. I think I bought them more than a decade ago, when I wanted more channels than the system I was using could do. I didn’t just buy another one of it, or its next generation that did support many more channels, because it couldn’t measure the power when on my generator. Years later, I still hadn’t found the time to do the project and I ran across IotaWatt. It looked like a good solution and I liked that it was open source. So, if I was really motivated, I could improve it. I find that IotaWatt gives me good data, from which I can generate information. That information allows me to make decisions.
If the data was 10 times more accurate, it would not change the decisions I would make. I recently started publishing my data to InfluxDB, but I used IotaWatt by itself for more than a year and was happy with the information I got out of it.
I believe more channels are more interesting and so also use Sonoff devices running Tasmota to get data on particular appliances. I started with my dehumidifier, but am adding the capability to all of my devices that are automatically controlled.
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Thank you so much for the replies. So what I’m looking for is just a way to get this data into InfluxDB and no real need for onboard storage. From what it sounds like both work fine though using a ADC is simpler and supports reading more channels.
IotaWatt is a complete product that will do exactly what you need (and more).
The ATM90 is one component of many that would need to be designed, built, and validated to achieve what you want.
So, the choice is simple. If you want a project to create a system that will enable the measurements you want, before you can actually do the measurements, use the ATM90 or some other circuits. However, if you really just want to start making measurements as quickly and easily as possible, get an IotaWatt.
For your needs, there is value in the onboard storage:
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In the event of internet or influx server outage, the IoTaWatt will seamlessly backfill the missed using the data in the onboard datalog.
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Should you lose your influx database for whatever reason, IoTaWatt can resend up to a year’s history to recreate.
As far as I know, no other energy monitor will do that.
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I can confirm that the backfill of history works well. Had an HDD failure in my EmonSD and was a bit negligent in backups on it. IotaWatt backfilled the missing data and kept on going. I now have 2 of them since I just had solar installed. Waiting to flip the breaker on for the solar to get those readings going in.
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