Method and instrument for measuring the density of fluid media

A measuring device for measuring a density of a fluid medium, the measuring device comprising:

• a density sensor configured as a frequency oscillator with a mass balance;
• an evaluation unit connected to said frequency oscillator with said mass balance for outputting data;
• a base body having a first end and a second end with a counterpart;
• a cartridge carrying a connection part coordinated with said counterpart with which said cartridge and said base body are detachably connected to one another only at said second end, said cartridge having an inlet and an outlet for transporting the fluid medium in and out of said cartridge, said inlet and said outlet are disposed on a same side of said cartridge and on a same side as said connection part;
• measurement sensors, said frequency oscillator with said mass balance and said measurement sensors are disposed completely inside said cartridge and completely enclosed by said cartridge;
• and
• at least a memory disposed in said cartridge to store adjustment data or calibration data determined using measurement standards of said frequency oscillator with said mass balance, said memory coupled to said frequency oscillator with said mass balance;
• said density sensor, said evaluation unit, said cartridge, said base body, said measurement sensors and said memory configure a portable, handheld measuring device with said cartridge being an interchangeable cartridge.