Another option that might be easier for some people is if you have electronic fuel control where your gas setting is done with a potentiometer, that could be swapped out for a dual pot and then use a separate circuit running on the other side. It doesn't get you quite the same thing if your gas pressure isn't consistent, but it might be good enough and may be an easier/cheaper modification. I'm doing this on my 1Kg Diedrich (which came with that dual pot already installed) with Typica software.

I received another sales engineer reply from Amphenol that recommended their NPA Series of pressure sensors:

Please find attached, an application guide and data sheet for the NPA series of pressure sensors. While these parts could potentially meet most of your requirements, Amphenol Advanced Sensors makes no claim, nor are they considered to be, intrinsically safe (explosion-proof).

If you wish to move forward, please contact one of our distributors by using this link

https://app.mectronic.com/stkchk/stck5c ... 9bd0baba97

Similar to the other board-mount sensors these would need something to adapt the line to the pressure port (e.g., silicone tubing and a clamp or epoxy) as well as some electronics.

It'd be an interested homebrew project, but I've settled on the 267 Series from Setra and am just waiting for one with suitable range to show up on ebay.

I also struggled to find a propane-rated sensor, but I found one that works for me: a Rosemount 1151DP3 (full part number 1151DP3E12B1 in my case) "pressure transmitter." The measurement range is 0-30inH20 (0-7.5KPa), and it outputs 4-20ma. It's built like a tank and weighs about 12lb.

New, they are very expensive, but eBay has a pretty good supply of used or occasionally new-old-stock transmitters. The key is to search "1151DP3" the "DP" means differential pressure, the "3" means 0-30inH20 measurement range. I bought mine used for about $80.

I couldn't find documentation explicitly stating that the Rosemount 1151 is explicitly propane-compatible, but the wetted material is 316 stainless steel with Viton O-Rings, both of which are compatible with propane.

Here's a photo of mine, it's not small when compared to my Huky.

I'm still waiting on fittings to test the little sensor I acquired, but have the electronics adapted and ready to go:

This is so rad! Is the plan to seal the silicone tube with a compatible epoxy or do you think it'll be gas-tight enough on its own?

Another thought I had for homebrew gas pressure sensors is isolating the sensor in a compartment with something like an MQ-4 sensor. If gas was detected in that compartment you could alarm and shut off power to the sensors.

I am mainly interested in getting more precision in my gas adjustments, my chem engineering days are loooong ago...but would a simple water column indicator (basically a U turn filled with water) be safe to use next to an open flame? (in principle I think it should, it just feels like a whacky thing to do)
It'll be more precise than the standard manometer...

jpbbden wrote:This is so rad! Is the plan to seal the silicone tube with a compatible epoxy or do you think it'll be gas-tight enough on its own?

Another thought I had for homebrew gas pressure sensors is isolating the sensor in a compartment with something like an MQ-4 sensor. If gas was detected in that compartment you could alarm and shut off power to the sensors.

I'm not thinking too far ahead... for now, I just want this to hold together long enough to do a roast or two and see if it actually works. If it does, I think I'll go back to Mouser and try and find a sensor with a bigger nipple - something that's a much better match for the 1/8" barb, and that would let me use a thicker piece of silicon tubing between the two. I was thinking I might put a little silicone caulk on the connection, since it's flexible. For better or worse, I was thinking some flex would be a good thing for preventing leaks. Maybe rigid epoxy would not be a good thing, or would not stick to the silicone? I'm not sure...

I still would prefer a threaded connection, so will keep my eyes open on ebay for one of those style connectors that falls into the right range.

ira wrote:I don't like the hose stretched over the 1/8" fitting and wouldn't use that long term. I'd try soldering a piece of close fitting brass tube into the hole in that fitting to get something closer to the right size. and if that's to small, you can just solder another piece of brass tube over that.

Ira

Ira, I Agree. If this works, I think I should just chalk this sensor up to a learning experience and go find a sensor with a bigger nipple.

On the ABP2 Series datasheet, they mention the possibility of not needing clamps (p. 36) for working pressures < 15psi. They also mention the use of cable ties:



I have a Setra 264 laying around and cracked it open to check a commercial design. It has metal fittings on the exterior of the case. Inside, it looks like thicker-walled silicone rubber tubing and a rubber grommet for the connections to the board sensor. There was no epoxy or cable clamp on the tube-to-board sensor fittings, though the rubber grommet looks like it has a ring of epoxy and is being supported with the mechanical/screw connections of the pcb to the case. Working pressure of this unit is 0 - 0.25"WC.










Cracking open a commercial unit with NPT fittings, I would expect to see a similar setup to @aabud has with maybe something to hold the barb-to-npt fitting secure in the case. I poked around McMaster-Carr for a minute and didn't see a bulkhead-style barb-to-npt fitting, but I would be surprised if they are not out there somewhere...