What are the consequences of turning up absorption?
Increasing the computed distance from the receiver to the BLE device, and subsequently potentially placing it out of range depending on what your configured max reporting range is.
What unwanted results would I get if I unnecessarily used the maximum absorption value?
Your BLE device will likely be reported as not seen by this receiver, due to the increased computed distance from the receiver.
Why isn’t absorption set to a value greater than zero by default?
The espresense code writer doesn’t know the physical characteristics of your specific receiver deployment to come up with a reasonable value. He is offering you this variable as a method to calibrate to your specific circumstances.
Here’s a short description as I understand it -
You have a BLE receiver, and a BLE transmitter. The signal strength of the transmitter as seen by the receiver is how the distance between the 2 are calculated, e.g. the signal strength is the only “measured/known” value of the receiver for a specific BLE device ID that varies as you get closer/father away. Problem is, you want distance between the two.
Distance is a fixed formula of known loss of power over free air for the given 2.4Ghz signal frequency. In other words, received power level diminishes at a known rate over a given distance for a given frequency in free air.
Calculated distance will be a factor of multiple unknowns - What is the transmitter’s original power? What objects are in the way that will increase the loss over distance vs free air?
The Calibration section of the software attempts to account for these unknowns. Original power is the first item “Rssi expected from a 0dBm transmitter at 1 meter distance” and defaults to -65 which is the default for most BLE transmitters. That said, you can change that value on the transmitter, so here you can specify the change (note for this to be useful, all transmitters would have to be adjusted).
What objects are in the way that will increase the loss over distance is the second item asked about, “Factor used to account for absorption, reflection, or diffraction”. Entering a value here will reduce the expected receiver power for a given distance because something that absorbs, reflects, or diffracts 2.4Ghz is in the way. This value is a SWAG. The idea is to tweak it and compare your transmitters actual distance to the software’s reported distance to make them as close as possible at several known distances.
Most people aren’t going to go through the effort (I haven’t) but the options are there if you really want accurate distance reporting.
Long winded, but hope that helps.