My wireless gadgets have been working non-stop. They even went to the mine and survived an extensive test underground. I had to troubleshoot an overheating Sandvik dumper truck - it was suspected that the pump that was driving the fans was malfunctioning - so I had to monitor and log the parameters during the dumper's operation - i.e. when it was hauling 50 tons of ore up the ramp. Doing the monitoring while riding in a pick-up behind the dumper is extremely convenient.
We have a state of the art HMG 4000 - and it is indeed a super capable logger - but if I had it with me on this job, I most likely wouldn't be able to do all the logging and monitoring that I did in such a comfortable and easy way.
I am also extremely surprised that my transmitter survived the "splash damage"! The 3D-printed enclosure has the IP rating of exactly zero, and as I slapped one of the transmitters on top of the engine cover, I forgot to put it inside a plastic bag - and we did a complete run with the transmitter completely exposed. In some places, there's a lot of water dripping from the ceiling, but miraculously, no damage or even malfunction occurred!
Of course, as I expected, inside the tunnels the signal would be lost as soon as the dumper would turn around the corner, but in all situations, I was able to get the connection back, so the software is solid.
Another interesting thing - I noticed that the Gems pressure transducers have a drifting zero (either the sensors or the ADC itself), so sometimes the zero shifts by a 0.1-0.5 bar, but the zero-shifting function in the App corrects this instantly. In a couple of months, I will re-test the system against a "proper" gauge once again to see if I detect any accuracy issues. What I find interesting is that the shift is not permanent, and sometimes goes away, but it is still within a couple of ADC counts - so I guess this can't be considered as anything problematic.
As I am moving towards building the MVP - I want to show off the current design, which brings some changes and improvements based on what I learned during the last months.
Like all engineers - I want it all. And I want it all at the same time, which is impossible. However, I believe that I came up with a solution that makes it all possible. Allow me to explain what I mean by that:
I want to be able to swap sensors easily using a magnetic snap connector, and I don't want to swap sensors at all.
I want to be able to connect three channels, and I don't want an expensive multi-channel arrangement for a simple single sensor use case.
I want to have an ability to connect a DS18B20 temperature sensor, better yet - two temperature sensors (for delta T measurements), but I don't want to pay for the one-wire interface IC.
Wait... even better - I want to be able to connect eight DS18B20 sensors... Why eight? Who knows why! Because I can! (Just kidding here, - because there's an eight-channel one-wire serial chip, that's why). I still don't want to pay for it unless I need it.
I am also putting everything in a proper ABS enclosure, with panels on each side, and enough space inside to house one compact pressure sensor.
So - if you want a sensor inside the enclosure - you can have it. If you want it outside, and use a swappable magnetic connector - you can have it. Don't want to use a swappable connector, but prefer a standard industrial M12? No problem - just install it in the panel. Maybe you fancy using a multi-pin D-connector? As long as it fits - you can use whatever you like!
For me - the killer combination (at least from the hydraulic technician standpoint) - is the box that has a pressure sensor inside the enclosure, and two wired connections to connect a flow sensor and a temperature sensor, which is why, by the way, I am adding a third analog channel (a slower one) - which will allow monitoring a third parameter, like the temperature. I have been using the transmitter with Parker and Hydac flow sensors, however since the current hardware has only two channels per transmitter - I have to use a second transmitter to monitor the temperature sensor, and the temperature is important. Putting all three (flow, pressure, and temperature) in a single transmitter is a big plus!
The renders to the left represent this combination. So the box alone works as a pressure gauge, but when you need to connect your flow meter to it - you use two cables to connect the transmitter to the flow and temperature sensors, and a test hose to connect the pressure gauge.
It's a win-win. No need to carry around a large logger and deal with wires whenever you need to connect a pressure sensor just to measure pressure in a single point. But - with the ability to expand your gear to a full-blown flow meter when you need to.
The modular DIY side also contains a surprise. I can't tell you right now what it is, but I will when I get the PCBs and have at least one mounted and tested. (I just ordered a test batch of PCBs exactly five minutes ago). All I can say right now is that if this thing works - I will be able to solve my "Parker -related" beef that I have had for quite a while now... The details will be revealed in a separate post!
Another change - I am going to use a membrane graphic overlay for the power button - which makes the system much more protected against moisture and dust, and I am going to use an IP67 USB port, which will be also placed on the front panel.
I have the enclosures, I am waiting for the PCBs. My next step will be assembling a couple of these newer systems, tweaking the firmware and the App to add the third channel and the DS18B20 temperature sensor interfaces. (I want to bring these temperature sensors to hydraulic equipment diagnostics and see how they fair). And finally (this will be the first thing that I will do) - I will test the "mystery part" of the new PCB and will write about it as soon as I have any results!