Hadn't seen this mentioned but perhaps I missed it, more plumbing hardware than electronic, but perhaps useful for others.
Having tried a variety of plates and heat-sink compounds and tie-wraps to hold these little chips in position on small sections of metal pipe (my rads are fed with fused plastic pipe), I came up with the solution of using pipe clips, the cheap plastic variety from DIY stores and hardware merchants.
The first problem hit was with attaching plated sensor the the boiler clamp nut, it was off by 10c and no way could I get a more accurate reading, presumably angle? Finally found a pipe clip which got hacked in half to fit in the tiny gap in the photo... Some hacking with a Dremel, some soldering to a pin connector, some fiddling around with epoxy and voici....

The gap
The tie wrap in the top of the photo is the original plate mounted version which was "off"..

Having scored on that front with more reliable readings I looked at the roving radiator test kit and realised the same solution might apply so epoxied the chip on the end of some telephone line in a 22mm clamp and it works a treat. Cable and chip fit neatly into the screw-hole, flood with epoxy and done. The pipe it fits is 21.5mm so tighter than a duck's rear end...

As said, a tight fit to a twinwall radiator feed pipe, and a complete swine to get back off even with pliers, but no broken wires or oopsies to contend with, and so much faster to fit.
For those looking to measure metal pipe temperatures, possibly an unusual if fiddly solution, but no need of tie-wraps in the latter case...

Not so much a MySensors build as an example of how even the most basic information can inform changes for the better, in this case space heating.

The system here is fairly basic, an array of DS18B20s, some ultrasonic tank probes and a gas reed sensor, temperature is updated every 5 minutes, the gas updates every 0.05m3...
With winters here down to -20, the first priority last year was insulation, and even though a modern house, the gas bills essentially halved over the year, effectively funding not only the insulation, but replacement axial radiator valves and thermostat heads (Heimeier) to replace the typical arrangement of unknown origin, with spare... But now the MySensors impact..
This autumn's attention turned to the central heating unit, a modern combi unit of good manufacture, installed by a 'certified' heating engineer, but aside what little I knew about condensation boilers and the steep learning curve that followed, I was bemused by the return from the radiator loop almost burning my finger within 10 minutes of the system being fired up. This did not make sense for what I understood of a condensing boilers, which compelled a look inside for the first time, the manual and some googling.

The boiler is a 25kW combi with minimum output 7.6kW, the radiators account for ca 13kW at Delta 60 set for 15c drop (previously set ca 20c drop), settings since day one were 65c and the pump was set at max output of 3, last year's -20 resulted in 13.5m3/day gas consumed, not crazy by historical records, but hmmm.
So now comes tinkering with data from MySensors via Domoticz to inform...
Currently the boiler is set at 55c, the pump is on Low (40 v 84w), but the results are surprising - Slower rising temperature when ON, 42 minutes v 25, but gas use dropped from 0.75 to 0.6m3, but here's the kicker from that longer heating time, not only less energy used per cycle, but longer and thereby fewer cycles per day. Current evaluations are between 15 and 20% savings, so thank you to all the MySensors community and contributors..

Surprised I'm not bald will all the hair pulling and failed attempts to get there but after a year it is finally working...
The task was simple enough, to measure fluid depth in two tanks, one a sewage holding tank, the other a bulk water tank. Just figuring out which method worked with which board was an exercise in frustration, but the JSN-SR04-2.0 turned out the only one of the two I could get to reliably work.

Despite the industrial look, these waterproof light switch enclosures proved ideal, as the batteries in holders fitted beneath the clear plastic. A little hacking out of the switch 'fingers' with a Dremel gives plenty of space in the base area.
Battery holders are held in plastic conduit which are hot glued to the back of the box poking through the front section aperture.

The top case is a 3v3 WhisperNode with onboard RTC and RFM69, and tucked under the spaghetti in the top left back corner is a level converter. The RTC wakens the Node every hour to initiate readings, and despite a few hiccups seems to be reliable. The WhisperNode is allegedly capable of draining the 2 AA cells down to 0.9v, time will tell...

The lower box holds the 5v ProMini, a small latching relay, and the ultrasonic board, the button type ultrasonic (like parking sensor) is mounted on the end of a 3/4" collar to 1/2" galvanised steel tube drilled centrally through the roof of the 1.34m x 1.67m tank area.

Connection between the cases is via Cat5e in 16mm conduit, 2 cores for I2C, 3 cores for relay control and 3.3v power, 2 cores for 5v and ground to the level converter.

Despite worries over echoes in the resulting space, the tank was emptied last night, and the reading is coming in with the occasional glitch at 1620mm depth from the head, which I believe has a cone angle of 45 degrees.
The Node control of a Relay by On/Off pins to Mosfets may seem wasteful, but I had them anyway. The 5ms on/off of this small latching signal relay boots up the ProMini and seems reliable.
Still to incorporate a WDT/Reset on the 5v as it periodically hangs, and a time limiter on the Node to complete the task, but glad it is all all working semi-reliably, even if some of the programming side I still don't understand...
The 5v tests for 2 consecutive identical readings, the 3.3v tests that it fits within acceptable range, and if not calls for a further reading.

Once delivery of a second identical board from China is done, the water tank should be a lot easier. This one is the more important, as ran out of water previously due to corrosion of the level probes in the tank (3 core cable and short bolts) which stopped the borehole pump topping up the tank, and the hidrofor hit it's cut-off electrode. The level monitoring will give early warning to go investigate long before the bulk tank is 'empty'...

Postscript 12/7/18 - Water tank worked flawlessly from first deployment, but led to concerns over dropping battery voltage.. The problem appeared to lie with the Master sinking power through the I2C lines, but a routine to null the SDA/SCL lines prior to sleeping seems to have halted the decay.
One of the unexpected results of the Sewage Tank deployment was detecting a dramatic rise in level during a heavy storm (85mm in 24 hours) initially thought to be ground water intrusion.
Excavation to the incoming pipe connection to the tank found a round pipe in a square hole (not exactly an unexpected building practice here, now packed out and sealed.
Losing 30% of storage capacity would otherwise never have been detected, so it the deployment has already paid for itself handsomely...

@pepson This reminds of that famous quotation "Any ship can be a Minesweeper..."
"Once...."

@neverdie Would this work ?

@sundberg84 Yeah, this brings back memories, particularly of quite a few hangovers.
I used 3 and four wide fireclay pipes for bottle storage, they were used for ducts back in the day before plastics took over, cable went optic fibre. I noticed recently here they are back in stock in stores as....yep...wine storage racks.... but wacko pricing relatively...
The beauty of the fireclay was it's slow temperature and humidity change, and this formed the bulk of the thermal mass in the cellar I made below the floor.
I used a 150mm glazed ceramic drainage pipe dug in under the garden as a loop (rope caulked joints - anybody remember them), from memory down about 1.5m, both avoiding frosts and baking sun, don't think the temperature varied over a degree all year round, the ground acting as a massive heatsink which maintained a constant temperature all year round.
Only when the hatch was opened did the temperature jump, a small fan kicked in when the hatch was closed and ran for 30 minutes, a second contact switched on the lights and shut them off, long before LEDs were so prevalent, old reliable (until you were depending on them) incandescent bulbs.
That was it really.
Biggest problem I found was humidity in the early days, probably the fresh construction...

@tbowmo Hah, you were lucky, I finally upgraded from the monochrome to colour...

@sundberg84 Easy, one is disconnected... At 90 degrees?

Finally the round-tuit UPS got built after the last power cut clobbered the Controller/Gateway system, lesson learned...
Meanwell AD-55A, 7.2Ah Acid gel battery, two usb 5v buck converters, a spare socket for raw volts, and a 15 euro IP66 box from the local shops.. Some drilling and filing to the lid, couple of brackets, spare bolts, banding, soldering and hot glue...
A bit bulky, but disappears in a void under the stairs, two tiny drill holes let the buck converter leds shine threw...
No monitoring as yet, but sailed through a power cut this morning and the Pi didn't skip a beat.. First up is the Pi's RTC then can put the cover back on the Controller...

First of the winter projects done, just the programming to finish and replacement temperature chips to get (broke the legs off both DS18B20s through clumsiness).
With mains/battery backup and RTC, it will record boiler start/stop and run times as well as feed/return temperatures, and as an aside the inevitable power cuts which plague this part of the world.
The MCU plugs into a socketed backplane hot-glued to the back of the box should removal prove necessary, but quite pleased it is sturdy and all fitted into a slim 25mm deep standard (cheap) box.

@Yveaux Yes, but was hoping someone had already gone through similar experiments, and could advise what did/didn't work
Your post prompted a reminder there is a 1/2" valved drain cock for the water meter/PRV in the bathroom... This would simplify testing without having to make plumbing alterations for the final locations

Didn't find exactly what I was looking for in a forum search...

Bought two of these (Chinese?) pressure transducers and 1/2" adapters with the intent of monitoring pressure (initially at 2 points) in the pumped water supply which has various headlosses in the line.
These are listed as 5v supply, 0.5-4.5 output for 0-0.5MPa, 20mA consumption, beyond that only claims the response is "perfectly" linear.

The Node is 3.3v, 5v is available on-board from an external PSU, but the voltage output will have to be scaled down to suit the ADC pin, even more so if aiming for Vref 1.1.
Normally a high value resistance ladder would suffice, but concerned over effect on response (presumably a variable resistance device), checked output resistance to ground, at atmospheric ca 6.7 Mohm, purportedly corresponding to 0.5v.

It occurred to me that if it IS a variable resistance it should also function the same at 3v, so any here able to offer any insights, experience, or tips ?

@amkochaki You imply the sensor sends two different voltages, one for standby and one for active, perhaps you might establish what these voltages are for each condition.
All your ADC is doing is measure the voltage, your sketch takes that value and converts that to a logical 1 or 0, standby/active.
If the voltage swing is large, say 5v for stable and 1v for triggered, perhaps conversion via resistor divider can provide a logical 1 or 0 input simplifying the process ?

@Encrypt It sounds as if you are making progress, moving off breadboard will certainly make for greater reliability.

My reasoning for checking HIGH and LOW is that these are fixed states rather than in transition. FET type sensors are very fast, but the Elster Water Meter Node would send an intermittent false increment (No idea why/what), which is why the additional check on pin state was introduced.
That pin check was spurred by experience with the Gas Node, which gave rapidly escalating readings, found to be caused by the reed closing for ca 6 seconds. Checking in a Sleep loop that the pin had changed back from LOW to HIGH before going deep sleep resolved it, 3 years on it's still in complete sync with the register.

@Encrypt Sorry, meant to respond to this when you posted it but got distracted again...
If I recall correctly the calls to Gateway are limited to 7 or 8 attempts or thereabouts, but if your Gateway falls over every increment it will do the same. This can hammer Node batteries as I discovered after a power failure (regular feature) killed the Pi3, now solved with a DC/DC UPS.
Never had comms issues with the RFM69 on 433MHz but they do use proper whips.

Have a similar setup with an Elster sensor, but by the time the water meter was done I'd learned from similar "issues" from my first ever Node on the gas meter which uses a Reed...

Interrupt on FALLING was causing rapid cycles of the increment the trick was to ensure the increment only happened once on every wake from Sleep.
Set the interrupt to LOW, verify that the pin does indeed read LOW after wakening (in case of false triggers), increment the count, send the updated value, then verify in a SLEEP loop that the pin has indeed gone HIGH again before going to deep sleep.

Hope this helps

@mhkid If the suggestion by @mfalkvidd doesn't resolve the problem you might look at moving both Gateway and Node marginally to see if it it is some effect.
Clearly the Gateway can "hear" the Node but not the reverse, and as most transceivers are matched between power out and receive sensitivity, polarisation or influence from nearby objects may be in play. There can be some strange effects at 2.4 GHz, particularly where "shrunk" antennae are used.

It's kind of a hassle wasting 5 minutes, 2 - 3 times per day waiting on the gate to open, and the LONG wait for it to close just to make sure nobody sneaked in...
Looking at fitting a cantilevered sliding gate here so it traverses the -20 ice and snow (no bottom rail), but will be opening and closing it manually as it's way faster..
Plenty of manufacturers of gates depending on your locale, most of the kit here seems to be rebranded turkish, italian or chinese origin, but as sliding gates are usually driven by a fixed motor on a castellated rail they are slower than the hinged manual gates I already have.
And no remotes to fumble for...

@NeverDie Actually no. Because this is an EPA list denoting the effectiveness of listed products, it's much too complicated to find out concentrations of the active ingredient, and I would guess that the kill times have a Factor of Safety built in.
Saw nothing on what surfaces are referred as the Virus is known to survive on different surfaces for different durations, again I suspect a high FoS.
Sorted on "Follow the directions..." and looked for Human Coronavirus, ethanol and isopropol both pop up at 30 seconds contact (normal terminology for disinfection) time.

Hypochlorite is a few minutes but varies according to brand name, so not really helpful if you don't know concentrations.

My point remains that alcohol is readily available, and as an additional precaution post washing surfaces probably more than sufficient in a domestic environment.
If 70% is adequate for handwash on skin where it evaporates in a few seconds, no reason why on a cold non-porous surface it would be no less effective

@NeverDie An alcohol mist is pretty fast and effective as a surface disinfectant and almost universally available.
HOCl is a weak acid from vague memory and not so far removed from hypochlorite (same family?).
You have to remember that if a 20 second wash is good enough to clean your hands, the same should be true of surfaces, and raw produce rarely needs much other than a wash...
Sterilisation is a blanket attack so yes kills the bad stuff but also the good bacteria. eg - Chlorination provides you safe drinking water but kills some useful stomach bacteria on ingestion, which is why foreign waters give tourists problems the locals don't suffer....

@GLAB No worries, was in a similar situation.. My perspective was on what the Node could be made to provide, not what could be done within Domoticz to address the requirement - eg Had heard of Dummy counters but had no experience nor understood their purpose, nor had ever used scripts.
I had been sending a logical ON/OFF as well as a cumulative total from the Node and hit the same hair-pulling scenario as yourself.
Now only the ON/OFF is sent and the short script makes the transposition within Domoticz to a dummy meter (I think kWhr) using the internal clock in Domoticz.
Have fun