How are the remaining toner levels calculated?

[BoA_MPS]

I manage 400 devices on WJA and occasionally we have a device that is displaying 20% or 30% but the cartridge is actually empty.  I removed parts of the cartridge to check.  

I read a while back that the first 20% usage is used to calculate what would be the raining pages.  Is this based on the average toner density and pages printed for the fist 20%?    If so, a change in printing habits like a sudden peak for 2k pages monthly reports might be what is throwing the levels reported out by so much. 

[Valsimot]

Strange you have an empty toner while the level is 20%. Does that toner have a print quality issue so you replaced it and open? It should be other way the level = 0% and you still have some toner inside the cartridge.

The remaining toner is pretty accurate on laser printers.

[BoA_MPS]

Yes, the users report that the toner is no longer printing even though DCC and WJA are displaying 20% for instance.  I also confirmed that it is physically empty. 

The user replaced the toner and then counter on the DCC system and on WJA appears at 100%.  I opened up one of the "20 %" toners and it was completely empty.   We have seen this across several models on various revisions of firmware. I checked consumption run rates and a common factor is peak periods of print after the 80% when I believe the run rate for the level calculation has been calculated.  The is no physical sensor in  toner printers to measure physical levels. Typical models that we see this issue on are E87 series, E6 series, E52645.  

[Valsimot]

Yes, no sensor, only calculation based on pages printed and coverage used. It should be more accurate, unless the amount of toner is lover than advertised.

On the supplies status for an 20% toner you have information about pages printed, pages remained and coverage ?

[BoA_MPS]

Not at the moment. The engineers contacted me after changing the toner .  I have asked the to check the pages printed with those toners before replacing going forward.