Usually we at BitSim help create things that are physically small, like PCBs and FPGA configuration. If we have have to use a ruler longer than 10cm we consider something to be ”large”. Not any more. Last October we performed a validation test of our latest product, and that is quite a bit bigger.
The product allows synchronous measurements to be taken over a long distance. All sensors, in this case hydrophones, can be daisy-chained. For the prototype we had a cable of 500m between the controlling electronics and the first “node” that takes the measurements from the hydrophones and sends the data to the controlling node. After that we had 20 meters between the remaining nodes. Well that was the idea, we still needed to prove that it works.
To to that we, together with partners from the Uppsala University, went to test the system. Remember that we are used to small products? This one was so big, it needed to be transported on a trailer. Since we had assembled the system in Uppsala we went there to help packing and loading the trailer. After reading the manual of the trailer a few times and some trial-and-error we got the system on the trailer and were ready to go.
Everything is ready for the long drive to Ludvika
By the time we got to our hotel it was dark and we were hungry. Some of us had been to Ludvika before and said they had a good time in a pizza place. I won’ t go into details here, but now we all have memories of that pizza place, and all subsequent meals were compared to our first meal in Ludvika.
The next day it was time to find the place where we were going to perform the tests, somewhere in the forests above the one of the mines around Ludvika. It had been raining so the forest road was a bit wet. But we got there.
We started unpacking and while some of us were checking if the hole was blocked others went to pick up a generator and I started putting up the tent. When I was halfway it started to rain. I remember thinking “I can keep dry when putting in the last poles.”. When I finished I remember thinking “Why is it raining inside the tent?”. Among the tools we had packed there was a tarp which we put on top so we, and the computers were kept dry.
Once we verified the hole was not blocked, at least to a depth of about 500m, we sent down our system, well the part that is meant to go down at any rate.
Maybe I should tell a bit more about what were we going to do. The system will be used to form an image of the ground under the surface, using old boreholes. I don’t know much about how geophysicists create such an image, but I have seen them use graphs that look like the stuff you see on old seismographs. You know, those things that are used to measure earthquakes. Well, the idea is to make mini earthquakes and then capture the resulting waves. The hole has water inside, so using hydrophones we can record the sound waves, which are the result of reflections inside the ground. Mini earthquakes? Yes, mini earthquakes. This involved driving around a bobcat with a big weight that would hammer the ground. Remember the picture of the forest road? They did a similar test there.
We did two kinds of tests. One where we moved the hydrophones up and down, and one where we moved the bobcat. Why moving the hydrophones up and down? Well the prototype has 5 of them at a 10 meters interval. When analysing the data more hydrophones are needed. One way is to put more hydrophones on the system, which we can do, but another way is to do this like taking a panorama picture with your phone works. Take the first picture, move a bit, take another, move a bit more etc.. In this way we were able to measure the whole hole. Luckily the cable to the hydrophones was put on a motorized drum, so moving them up and down was easy.
After spending two days at the test site we were almost done and decided not to stop when it started to get dark, but continue so we could be done by the end of the day. Which we did. After packing and back-filling the potholes left by the hammering of the bobcat the field part of this test was complete. This gave us time to do something else the next day. We had been working with new technology for the mining industry for the last couple of days, so we decided to look at some old technology before driving home.
Where we went right at this crossing for the last few days, we went left this time. We spent some time looking at the Klenshyttan smelting house. I refer you to the website of the smelting house if you want to know more. With that visit the field trip was at an end, wel end. Only the drive home remained and that was nicely uneventful.
Oh, you are wondering about the other meals we had? Well, in my opinion both the Greek restaurant in the city centre as well as the Swedish restaurant next to the harbour had better food, but I won’t easily forget the pizza place.
By the time I write this, the data has already been analysed and we know the prototype functions. The data we acquired was not so interesting according to the geophysicists. They are already planning to take the prototype when they visit another site next year.