Thermal flow meter VA 500

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Product information
The VA 500 is a thermal mass flow meter for compressed air and technical gases. Designed for continuous monitoring and mobile measurements, it records consumption, supports leakage detection and helps optimise energy use and CO2 emissions.

Versions / Items

• VA 500 consumption probe, basic version: Standard (92.7 m/s), probe length 220 mm, without display | Order No. 0695 5001

Thermal mass flow sensor – principle and operation

• Principle: Two temperature sensors and a heater in the probe. One sensor measures gas temperature, the other is heated to a fixed temperature above the gas.
• Thermal dispersion: Heat removed from the heated sensor by the flowing gas is proportional to mass flow; the temperature difference is used to calculate mass flow.
• Signal processing: Temperature-difference signal is converted into digital outputs and standard flow units (m3/h, l/min, cfm, etc.).
• Monitoring and display: Real-time monitoring via integrated display (optional) or communication interfaces (Modbus-RTU RS-485 standard; optional Ethernet PoE, M-Bus).

Flow measuring ranges VA 500 for compressed air (ISO 1217: 1000 mbar, 20 °C)
1/2" (DN15 / 16.1 mm) | 759 l/min (26 cfm) | 1516 l/min (53 cfm) | 1836 l/min (64 cfm)
3/4" (DN20 / 21.7 mm) | 89 m3/h (52 cfm) | 177 m3/h (104 cfm) | 215 m3/h (126 cfm)
1" (DN25 / 27.3 mm) | 148 m3/h (86 cfm) | 294 m3/h (173 cfm) | 356 m3/h (210 cfm)
1 1/4" (DN32 / 36.0 mm) | 266 m3/h (156 cfm) | 531 m3/h (312 cfm) | 643 m3/h (378 cfm)
1 1/2" (DN40 / 41.9 mm) | 366 m3/h (215 cfm) | 732 m3/h (430 cfm) | 886 m3/h (521 cfm)
2" (DN50 / 53.1 mm) | 600 m3/h (353 cfm) | 1197 m3/h (704 cfm) | 1450 m3/h (853 cfm)
2 1/2" (DN65 / 68.9 mm) | 1028 m3/h (604 cfm) | 2051 m3/h (1207 cfm) | 2484 m3/h (1461 cfm)
3" (DN80 / 80.9 mm) | 1424 m3/h (838 cfm) | 2842 m3/h (1672 cfm) | 3441 m3/h (2025 cfm)
4" (DN100 / 110.0 mm) | 2644 m3/h (1556 cfm) | 5278 m3/h (3106 cfm) | 6391 m3/h (3761 cfm)
5" (DN125 / 133.7 mm) | 3912 m3/h (2302 cfm) | 7808 m3/h (4594 cfm) | 9453 m3/h (5563 cfm)
6" (DN150 / 159.3 mm) | 5560 m3/h (3272 cfm) | 11096 m3/h (6530 cfm) | 13436 m3/h (7907 cfm)
8" (DN200 / 200.0 mm) | 8785 m3/h (5170 cfm) | 17533 m3/h (10318 cfm) | 21229 m3/h (12493 cfm)
10" (DN250 / 250.0 mm) | 13744 m3/h (8088 cfm) | 27428 m3/h (16141 cfm) | 33211 m3/h (19544 cfm)
12" (DN300 / 300.0 mm) | 19814 m3/h (11661 cfm) | 39544 m3/h (23271 cfm) | 47880 m3/h (28177 cfm)

Features and benefits (summary)

• Thermal mass measurement with low pressure drop and no moving parts.
• High accuracy and fast response suitable for leakage detection and consumption monitoring.
• Selectable display units and adjustable parameters (diameter, counter reset, reference conditions, 4...20 mA scaling, pulse weight).
• Digital interfaces: RS-485 (Modbus-RTU) standard; optional Ethernet PoE and M-Bus. Analogue 4...20 mA output and isolated pulse output (configurable).
• Compact stainless-steel sensor tube, easy installation (G 1/2" / 1/2" NPT male thread or inline versions available).

Technical specifications

• Model: VA 500
• Order no.: 0695 5001
• Brand: CS-Instruments
• Sensor type: Thermal mass flow sensor (thermal dispersion)
• Measured media: Compressed air and gases (configurable: air, nitrogen, argon, helium, CO2, oxygen, vacuum)
• Display units: m3/h, m3/min, l/min, l/s, ft/min, cfm, m/s, kg/h, kg/min, g/s, lb/min, lb/h
• Accuracy: ±1.5% of measured value ±0.3% of full scale (on request ±1% of m.v. ±0.3% f.s.)
• Operating temperature: Probe -30...110 °C; Housing -20...+70 °C
• Operating pressure: -1...50 bar (for pressure > 10 bar order additional high-pressure protection)
• Digital output: RS-485 (Modbus-RTU) standard; optional Ethernet (PoE), M-Bus
• Analogue output: 4...20 mA for m3/h or l/min
• Pulse output: 1 pulse per m3 or per litre, galvanically isolated; pulse weight configurable; can be used as alarm
• Supply: 18...36 VDC, 5 W
• Load (4-20 mA): < 500 Ω
• Housing: Polycarbonate, IP65
• Sensor tube: Stainless steel 1.4301; insertion length 220 mm; Ø 10 mm
• Mounting thread: G 1/2" or G 1/2" NPT male thread (inline/threaded variants available)
• Housing Ø: 65 mm
• Mounting position: any
• Weight: approx. 3.5 kg