Flowmeter - Pulse and 4-20mA Data Logging

Hardware
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I have a GPI TM Series flowmeter (2in, TM Series (Water Meters) - FLOMEC) and I am considering adding their 4-20mA module (https://s3-us-west-2.amazonaws.com/catsy.467/4-20mA-module-owners-manual.pdf), which has both 4-20mA (flow rate) and pulse (volume, one pulse per gallon) capabilities. The pulses are Open Collector (NPN), Current Sinking.

I know NCD has this: https://store.ncd.io/product/iot-long-range-wireless-pulse-frequency-meter/ which would count pulses (if it can handle the above) and send them to a receiver, but I’m wondering how I can log the 4-20mA output at a certain frequency during each pumping session and send that to an Azure IoT db, say once per day, like at 3am when no one is there and we’re not pumping? Could I use a RPi and one of the 4-20mA Devices and a Shield? Is there a pulse-counting Device, so I can just have it all done by the RPi?

I have wifi/internet at the farm, and the flowmeter is <100ft away from one of the Ubiquiti mesh antennas. I can tap into the 220V circuit that drives the pump for power. I’d have a small battery to keep everything alive. This is in Belize, btw! I am in the US, but I want to build and test a solution before I head down there in a few months. I can’t test on that particular model of flowmeter, but I can probably fake up a proxy here using anything I can lay my hands on that produces a pulse, and anything else that cranks out 4-20mA.

2

Pulse counting really does not require any special hardware. You could do this with one of the GPIOs on the RPi. That along with one of the 4-20mA input modules we sell should be all that would be required.

If this is a high use case(you need several of these) we could develop a custom version of the IoT Long Range Frequency Meter devices with a 4-20mA input in addition so one device would do everything you need without the use of a RPi.

3

Thanks for the quick response, Travis. I think I’ll just use an optocoupler board for the pulses and get one of the 4-20mA boards so I’m not reinventing the wheel. I have a cheap Hall Effect flowmeter here, so that should suffice for generating pulse inputs. Looks like going with 24Vdc is probably easiest, given that’s the industrial standard.

There’s already a standard method published for streaming RPi data to Azure using node.js, so having the RPi makes my life a little bit easier!

Once again, thanks!

Neil.

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4

By the way, store.ncd.io has an out-of-date certificate, might want to get that looked into.

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5

This seems to be a bug somewhere. If you look at the certificate for the site it doesn’t expire till the end of February. We are looking into it though.

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