Hydraulic reservoirs and gearbox lube tanks usually grow their instrumentation one retrofit at a time: a float switch here, a bimetal thermometer there, a breather filter on the remaining port. The Buhler NV 74 condenses that pile onto a single DIN 24557 T2 flange.

Why combine level contacts and temperature sensing in one stem?

Every additional port on a tank is a potential leak path and another part to stock. The NV 74 carries up to 4 magnetically coupled reed contacts that reposition without tools, in NO, NC or change-over form, each switching up to 2.5 A directly. The same stem accepts a bimetal temperature switch fixed at 50, 60, 70 or 80 deg C, a Pt100 Class B sensor, or a KT transmitter giving 4-20 mA over 0 to 100 deg C. Compared with fitting three separate instruments, the combined unit cuts tank penetrations from three to one and removes the wiring harness between them.

What changes between the standard and display versions?

The NV 74D adds an LED readout showing contact status and temperature at the tank, which maintenance teams favor on unmanned stations. Both versions share immersion tube lengths of 280, 370 or 500 mm in brass or stainless, and plug options from M3 DIN connectors to M12 circular types. Against simple single-point float switches, the Bühler Technologies GmbH design trades a slightly longer stem for the ability to set alarm bands after installation, and against electronic level transmitters it keeps the output as dry contacts that any PLC input can read without conditioning.