Siemens QBM81 Differential Pressure Switch

Siemens QBM81 is a differential pressure switch specifically designed for monitoring under and over pressure in ventilation as well as air conditioning plants. This tool has a pressure of 20 to 5000 Pa, single pole changeover output, an IP54 protection class and a temperature range of 0 to 70 °C. Differential pressure switch for monitoring air pressure in HVAC systems.The QBM81-... Differential Pressure Switches are used to monitor differential pressure, under pressure and over pressure in HVAC installations. Range is selectable according to model chosen (see measuring range in specifications).

By measuring differential pressure, they monitor the state of air filters, prevailing airflows, damaged fan belts and over pressure in clean rooms, kitchens, etc. They are also used to monitor differential pressure and positive and negative relative pressure in HVAC systems.

Application :

  • Monitors air filters, airflow and fan belts

  • Can be used to monitor pressure in clean rooms, kitchens, etc.

  • Easy to mount

  • Highly precise setting

  • Long term stability


Service Life > 1 000 000 switching cycles
Measuring range QBM 81-3: 20...300Pa
QBM 81-5: 50...500Pa
QBM 81-10:100...1000Pa
QBM 81-20: 500...2000Pa
QBM 81-50: 1000...5000Pa
Protection degree of housing IP54
Housing material Fiberglass reinforced polycarbonate
Cover material Polycarbonate
Permitted Media Air, non-corrosive gases
Ambient temperature (operation) -30....85°C
Ambient humidity <90% r.h (non-condensing)

Note: For more detailed specifications, please download the additonal documents