Siemens QBM81 Differential Pressure Switch (-3,-5,-10,-20,-50)


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.

Applications :

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

Specifications :

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



Housing material


Fiberglass reinforced polycarbonate

Cover material



Permitted Media


Air, non-corrosive gases

Ambient temperature (operation)



Ambient humidity


<90% r.h (non-condensing)

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

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