Thermal flow meter VA 521

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Product overview
The VA 521 is a compact inline thermal mass flow sensor for integration on machines and downstream of treatment units. It combines a removable sensor insert with modern digital interfaces for energy monitoring and process control. No inlet section is required due to the integrated flow straightener.

Flow measuring ranges VA 521 (max version 185 m/s) for compressed air (ISO 1217: 1000 mbar, 20 °C)
DN 15 | G 1/2" | 90 m3/h (50 cfm) | L 135 mm | B 55 mm | H1 50 mm | H 109.65 mm | A1 25 mm | A 20 mm
DN 20 | G 3/4" | 170 m3/h (100 cfm) | L 135 mm | B 55 mm | H1 50 mm | H 109.65 mm | A1 26 mm | A 20 mm
DN 25 | G 1" | 290 m3/h (170 cfm) | L 135 mm | B 55 mm | H1 50 mm | H 109.65 mm | A1 33 mm | A 25 mm
DN 32 | G 1 1/4" | 530 m3/h (310 cfm) | L 135 mm | B 80 mm | H1 80 mm | H 215.45 mm | A1 35 mm | A 25 mm
DN 40 | G 1 1/2" | 730 m3/h (430 cfm) | L 135 mm | B 80 mm | H1 80 mm | H 215.45 mm | A1 36 mm | A 25 mm
DN 50 | G 2" | 1195 m3/h (700 cfm) | L 135 mm | B 80 mm | H1 80 mm | H 215.45 mm | A1 44 mm | A 30 mm
Other gases: same characteristics apply for Ar, CO2, N2O and natural gas (NG).

Advantages of VA 521

• Compact inline design with removable sensor unit for maintenance without removing the measuring section
• All interfaces configurable via the local display
• Modbus-RTU output (RS-485)
• 4…20 mA analogue output for instantaneous flow
• Galvanically isolated pulse output for totalised flow; pulse weight configurable; can be configured as an alarm relay
• Optional interfaces: M‑Bus, Ethernet or PoE
• Optional integrated pressure sensor for compensated measurements

Technical specifications

• Model: VA 521
• Sensor type: thermal mass flow sensor
• Measured media: compressed air and other technical gases (configurable via service software/data logger: Air, N2, Ar, CO2, O2)
• Measuring ranges: see table above (DN15…DN50, max version 185 m/s)
• Accuracy: ±1.5% of measured value ±0.3% of full scale (option: ±1.0% of m.v. ±0.3% f.s.)
• Operating temperature: -30…80 °C (with pressure sensor: -20…80 °C)
• Operating pressure: up to 16 bar (optionally 40 bar)
• Digital output: RS-485 (Modbus-RTU); optional M-Bus, Ethernet or PoE
• Analogue output: 4…20 mA for m3/h or l/min
• Pulse output: 1 pulse per m3 or per litre, galvanically isolated; configurable on display
• Power supply: 18…36 VDC, 5 W
• Input burden: < 500 Ω
• Housing: polycarbonate (IP65)
• Measuring section materials: aluminium, 316L stainless steel
• Connection threads: G 1/2" to G 2" (BSP) or optional 1/2" to 2" NPT
• Mounting position: any
• Weight (typ.): 3.5 kg