201-63 What is the function of water level observation window of fisher sub sieve sizer?

201-63 What is the function of water level observation window of fisher sub sieve sizer?

The water level observation window of fisher sub sieve sizer is located at the upper left of the front of HMK-22 Fisher sub sieve sizer. It is used to observe the water level situation before the voltage stabilizer works.

HMK-22 Fisher Sub Sieve Sizer

Fisher Sub Sieve Sizer https://www.labulk.com/hmk-22-fisher-sub-sieve-sizer/