How can I measure the scale in water? I have hard water in my house. All the taps have tartar around. It generates some problems in some of my home appliances so I have bought polyphosphate salt but when I boil water I don´t get the expected results.
I´m looking for some product or filter that would make the water in my house better for drink and use. That´s is why I´m evaluating to install a filter with polyphosphate salt or a floating dispenser (like a buoy).
I´m now trying to make a test before installing the floating dispenser I have recently bought in my water tank so, this is what I have done:
First I have filled a pan with water and boil it until it got empty and this was the result:

Then, I have use the floating dispenser in a pan with polyphosphate salt for 30 mins. After that I took out the dispenser and boil it until it got empty. This was the result:

It seems like there is no difference.
How can I make a better measurement or treatment? Is this the right product for my problem? 30 minutes is enough to the polyphosphate salt? Do you think that will be better a floating dispenser or the filter with that product? Maybe I have to buy another kind of filter?
Most drinking water has residue like what you are showing.  Boiling water shows there are ions in the water, but it does not show what kind of ions are present.  Boiling water is practically useless when determining scaling potential and it is not safe to do using cooking pots and pans.  Part of the reason laboratory equipment is more expensive than cooking pots and pans is because lab equipment has much better fire prevention measures.  Boiling down water in this manner has the potential to start a fire.
pH is a better measure for scaling potential.  If you want to get technical, water pH is used to determine the Langelier Saturation Index or the Ryzner Index which are indicators of scaling potential.
Your water is probably too alkaline. Alkalinity and acidity need to be balanced because if water is too alkaline then too much scale forms; however, if the water is too acid pipes corrode.
For a household, filtering water with an activated carbon filter first, then an ion exchange filter might work.  Ion exchange filters contain a resin which exchange scale forming ions like calcium with ions like sodium. These filters can be easily fouled by organic material, so the organic material will need to be removed by something like an activated carbon filter.