In my last post I talked about how I installed a Shelly BLU Distance in my heating oil tank to measure how much oil I had left. Everything worked fine, though after a few days there have been no updates to the levels – despite lots of oil being used to heat my house and hot water.
Looking closer at the installation instructions, it outlines the following:
When installing the device parallel to a surface, ensure it is at least 20cm away from the surface (e.g. walls) to prevent inaccurate readings due to wave reflections
As I showed in my previous post, I had most of the device sticking out of the top of the tank, which meant there was very little inside the tank. Based on my calculations, it looked like only 14mm of the device was actually inside the tank. If the instructions were looking for 20cm clearance around the sensor, I was not doing that as the tank is curved and infringing on that.
The Change
It is an easy fix, have more of the BLU Distance inside the tank, so that there is the 20cm clearance around it. All I did was remove the screwcap that came with the tank, and adjusted the mounting nuts to allow the device to sit lower down.
I was a little apprehensive about this change (a) how it might affect signal strength, (b) how it affects the measurements. The device already has a minimum 200mm measurement which is a significant portion of my tank it cannot read, by putting the device deeper in the tank I can now measure even less of it.
Results
In terms of signal strength, I actually found that the dBm measurement is almost exactly the same as before. This leads me to believe that the BLE aerial in the device is actually closer to the sensor tip than on the other end as I had initially suspected. This is an interesting design choice and might affect those even more with metal tanks. In fact I am seeing slightly better signal strength after going deeper inside the tank a little.
I will update this post with results on the oil measurement frequency and if re-positioning the device actually changed anything for me.
I would love to hear from you and your experiences using the Shelly BLU Distance. Contact me on github