• The unit is calibrated at the factory (for operation with 16 mm diameter glass tubes) and keeps calibration without power supply.
• The operation principle is based on measurement of optical density with digital presentation of results in McFarland units

Two versions of the product are available:
DEN-1 powered from external energy supply.
DEN-1B powered both from external energy supply and from batteries (АА). 

Certified reference material, neutral density glass filter set of 4 Abs calibration points - 0.3532, 1,0512, 2,0425, 2,927 (the values may vary slightly from batch to batch)