The Fischer Mess DS21820A21BK0000 is a dedicated electro-mechanical vacuum and underpressure differential pressure switch belonging to the heavy-duty DS21 Series engineered and manufactured by FISCHER Mess- und Regeltechnik GmbH (Germany) – a globally recognized pioneer in precision industrial pressure and flow control instrumentation. The instrument is specifically developed for reliable underpressure, suction draft, and vacuum differential monitoring across demanding industrial environments where robust mechanical switching is essential.

The instrument incorporates a rugged pressure chamber constructed from die-cast aluminum combined with a high-sensitivity measuring diaphragm calibrated for a 0..250 mbar (0..25 kPa) differential span. Diaphragm movement induced by vacuum or suction pressure differential is mechanically transferred to two independent microswitches (2 x SPDT potential-free changeover contacts). This dual-switch arrangement allows operators to configure two distinct setpoints across the span (e.g., Switch 1 for an early warning alert on declining vacuum levels and Switch 2 to engage auxiliary vacuum pumps or trigger emergency shutdown). With an IP55-rated protective enclosure, dependable overpressure/vacuum proofing, and proven long-term switching repeatability, the Fischer Mess DS21820A21BK0000 serves as the optimal switching solution for industrial vacuum packaging equipment, robotic vacuum lifting grippers, flue gas exhaust draft controls, and suction-line filtration systems.

• Manufacturer: FISCHER Mess- und Regeltechnik GmbH
• Brand Origin: Germany
• Full Order Code: DS21820A21BK0000
• Product Classification: Industrial Vacuum / Underpressure Differential Pressure Switch (DS21 Series)
• Dedicated Function: Vacuum and underpressure differential monitoring with dual-stage safety limit switching
• Pressure Mode: Unidirectional differential pressure / Vacuum differential (0..Δp)
• Service Media: Air, exhaust gases, flue gas drafts, and neutral industrial gases non-aggressive to aluminum
• Measuring & Switching Range: 0 to 250 mbar (0 to 25 kPa)
• Switching Outputs: 2 independent microswitches (2 x SPDT potential-free changeover contacts)
• Switching Operation: Individually adjustable setpoints across the measuring span for dual-stage control (Alarm / Trip)
• Contact Electrical Rating: 250V AC, 5A / 24V DC, 3A
• Switching Reproducibility / Accuracy: ≤ ±1.5% to ±2.0% of full scale (F.S.)
• Nominal Static Operating Pressure: Up to 2.5 bar – 6 bar (chamber dependent)
• Overpressure & Vacuum Safety: High unilateral proof capability without causing permanent diaphragm distortion
• Process Pressure Connections: Female thread G 1/4 (standard industrial port spacing)
• Measuring Chamber Material: Rugged die-cast aluminum alloy
• Diaphragm Material: High-fatigue resistant reinforced elastomer diaphragm (NBR / Viton)
• Outer Housing Construction: Impact-resistant industrial engineering polymer
• Enclosure Protection Rating: IP55 conforming to EN 60529 (Protection against dust ingress and water spray)
• Electrical Connection: Internal terminal strip with watertight industrial cable gland (PG / M20)
• Permissible Medium Temperature: -10°C to +70°C
• Operating Ambient Temperature: -10°C to +60°C
• Mechanical Mounting: Direct wall mounting or frame mounting bracket
• Typical Applications: Vacuum lifting and pick-and-place automated systems, industrial vacuum pump monitoring and protection, boiler flue gas exhaust draft surveillance, suction filter clogging alarm, and industrial vacuum drying chambers