Calorimetric flow sensor VA 521

thermalfor process monitoringair

Overview
The VA 521 is a compact inline flow sensor designed to measure compressed air consumption and other gases. It combines a small footprint with modern digital interfaces for connection to energy monitoring systems. The VA 521 is particularly suitable when a large number of machines must be integrated into an energy monitoring network.

Features and benefits

• No inlet straight length required — integrated flow straightener.
• Removable sensor unit allowing easy withdrawal and replacement.
• Compact design suitable for machine-level installation (downstream of equipment).
• Configurable display.
• Outputs: Modbus-RTU, 4…20 mA analog output, galvanically isolated pulse output (totalized flow).
• Optional interfaces: M-Bus, Ethernet or PoE.
• New option: integrated pressure sensor (optional).

Measurement ranges and dimensions (extract)
Measurement ranges for compressed air (ISO 1217: 1000 mbar, 20 °C). Values below correspond to available threaded measuring sections:
DN 15 | Thread G 1/2" | Full scale: 90 m3/h (cfm 50) | L 135 mm | B 55 mm | H1 50 mm | H A1 109.65 mm | DN code 25/20
DN 20 | Thread G 3/4" | Full scale: 170 m3/h (cfm 100) | L 135 mm | B 55 mm | H1 50 mm | H A1 109.65 mm | DN code 26/20
DN 25 | Thread G 1" | Full scale: 290 m3/h (cfm 170) | L 135 mm | B 55 mm | H1 50 mm | H A1 109.65 mm | DN code 33/25
DN 32 | Thread G 1 1/4" | Full scale: 530 m3/h (cfm 310) | L 135 mm | B 80 mm | H1 80 mm | H A1 215.45 mm | DN code 35/25
DN 40 | Thread G 1 1/2" | Full scale: 730 m3/h (cfm 430) | L 135 mm | B 80 mm | H1 80 mm | H A1 215.45 mm | DN code 36/25
DN 50 | Thread G 2" | Full scale: 1195 m3/h (cfm 700) | L 135 mm | B 80 mm | H1 80 mm | H A1 215.45 mm | DN code 44/30

Outputs and interfaces

• Modbus-RTU (digital).
• 4…20 mA analog output (for flow).
• Pulse output for total flow (counter), galvanically isolated.
• Options: M-Bus, Ethernet, PoE.

Applications
Designed for monitoring compressed air and industrial gas consumption at machine and plant level. Enables identification of potential savings, overloads and malfunctions, and allocation of consumption shares to production units.

Characteristics / technical specifications

• Type: compact inline flow sensor (calorimetric / thermal sensor principle).
• Model: VA 521.
• Reference conditions for ranges: ISO 1217 (1000 mbar, 20 °C).
• Available threaded versions: DN 15, DN 20, DN 25, DN 32, DN 40, DN 50 (connections G 1/2" to G 2").
• Max velocity: versions up to 185 m/s (variants exist).
• Power and display: configurable local display; digital interfaces for system integration.
• I/O: Modbus-RTU, 4…20 mA, pulse; options: Ethernet, M-Bus, PoE.
• Design: no moving parts, reduced maintenance, low pressure drop.
• Integrated pressure sensor: available as option.
• Use: compressed air and non-corrosive technical gases.