1.even when there are some remanant blood  and some solution, the uint can get precise data. 
2.double super large LCD display, can display how deep  the apex file has probed into the root
and digital display the distance from apex file to the apex at the same time, show the apex
length directly and clearly.  
3.with sona alarm, remind timely, more humanized.   
4.precision:0.1 
5.hooker and the wire can be sterilized with high tempreture, avoid cross infection.