Can I use an RIO MM1001 to natively measure natural gas flow through pulse output?

Hello all!

I want to measure the output of a rotary gas flow meter, and I am wondering if I can simply run my output wires into channel 1 of the GRV-R7-MM1001-10? Or if I will need a convertor or something in between?

This is the pinout of my rotary flow meter:
Pulse Output

And channel 1 on the RIO module says it supports “Pulse Measurement”.

Thank you!
Please let me know if I can provide any further detail.

Welcome to the Forums Luke!

Do you have a model number of the gas flow meter?
The pin out comes close, but knowing if its PNP or NPN or dry contact ect is pretty critical to knowing how to hook it up to a RIO

Hi Beno! Thank you

The model number is: NDM - 3M

I looked for more detail and found this description of the pins on the meter:
Wiring Photo

Before I dig too deep… Do you have an intrinsic isolation device?

I do not, the meter has natural gas moving through it, so it makes sense that we need to avoid ignition.
Once I find one of those, it’s basically a passthrough to the RIO, right?

Both the PDFs on that linked page don’t make any mention at all of the electrical interface.
That’s a real shame.

So to answer your question, the meter to intrinsic barrier is on the meter folks (ie, you will need to reach out to them before you buy the barrier to see if the meter will interface to it).

After you know which barrier you are going to use, we can then look at the output of the barrier (which I’m confident will have more electrical information than the meter docs) and guide you on how to interface the barrier to the RIO.

Probably not the exact answer you were hoping for, but since we don’t have anything to go on, its hard to answer wiring questions.

Hi Beno,

I have my next steps, hopefully I’ll get a meeting scheduled with the utility company in the next week.
The customer site is about two hours away from me, so I’m working with limited information from photos for now, thank you for bearing with me!

Thank you for your help! I’ll be back with details.

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Hello, I have returned.
It turned out that the customer’s gas meter uses a reed switch dry contact.
We wired the Opto22 like this:

And configured the RIO for “Switch Input, Powered Digital Input” and the RIO supplies the voltage for the switch.

Thanks for your help Beno, and hopefully this will help others in the future.


Thanks a ton for the follow-up. It was really helpful and greatly appreciated.
Glad you got it working.
Now, the fun part starts: doing the calcs and presenting the information in a meaningful way.


Did someone say monitor their gas meter?


As I like to say, anything is possible with Node-RED…


@torchard and I did the same with an old Logitec webcam, openCV and some Python to read my home gas meter.
Our meter was analog style, so had to defocus, ramp the contrast and then divide the ‘face’ into 12 and we looked for the pixel change as the hand moved over the background.
Worked great for more than 2 years and then the webcam setup had a… uh… side swipe with a wheeliebin and that was that.

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Awesome! I originally set up something similar for a 7-segment LCD (this program runs fine in an Exec node), but the above gas meter used a more complicated LCD so I had to spend some time getting it worked out.

Sweet! That’s a good solution.
We had a direct connection to the meter which provided pulses, so we didn’t go this route.

That was my plan A. The local gas company did not want to share anything and wouldn’t let me play with their meter, so I had to go with plan B.

Interestingly, the local electric company does it much better, and publishes one’s hourly usage data via a unique URL that is made available to all of their customers (no login required!).

Hi @luke.rector

This is the sticker on the back of our meter. Given your diagram above with the Rio (which uses 2 wires) and this sticker (which lists 6 wires), does it make sense which 2 wires I would use?

Looks like they provide two pulse outputs? If so, you can use orange and yellow or white and green. 100 cubic foot/pulse.

Thanks @philip

Will try it in the coming days and report back here…