The development of the new ECO 521 focused intentionally on the essential functions of measurement technology, with a custom-tailored sensor at its core. Precision, speed, and reliability, all packaged in a compact and waterproof housing, make this device a dependable partner for service and craftsmanship, sustainably supporting the green thumb in applications related to plant cultivation and agriculture, Made in Germany. The measuring devices can be used with the highly accurate sensor up to 5000 µS/cm, making them cost-optimized professional instruments for use in areas such as aquaculture, hydroponics, plant propagation, water treatment (e.g., reverse osmosis systems), boiler feed water, and heating construction. The long-term stable titanium measuring cell can be calibrated with GKL 100 calibration solution, and the integrated temperature sensor compensates for temperature changes very quickly and accurately. The ECO 521 is a reliable professional device for daily use, serving as an alternative or upgrade to entry-level measuring sticks.