The acoustic CTA  is a full-fledged hotwire bridge to perform dynamic flow velocity measurements in air. The calibrated velocity range goes up to 50m/s. Higher velocities are possible. Due to the measurement principle, the aCTA is particularly suitable for low flow velocities.The device can be used for other gases as well, in which case a special calibration is needed.

The aCTA is “plug and play” ready to use with hotwire probes of the type HWP10/xx. No presets or adjustments have to be made.
As output signal the device provides a voltage of ±10V. Based on the calibration data and the fluid temperature it can be converted into the flow velocity. An integrated 5kHz lowpass filter prevents alias-effects when using digital data aquisitions. Alternatively there is an unfiltered output for measurements up to 20kHz.

Additionally the flow fluctuations can be made audible through the provided headphones. This provides an intuitive and easy to use method to gain information about the quality of the flow.  Aerodynamic phenomena like turbulence, flow separation, shear layers, or periodic detached flow can be heard. This provides a powerful tool to detect areas that are likely to cause acoustic noise.
The headphones can be plugged directly into the 3,5mm phone jack.

The power supply has a wide input range from 9 to 18V DC. This makes it easy to use in automotive applications as well.

Technical Data
Measurement system
Velocity range 0.1 – 50 m/s, higher velocities possible
Frequency resolution 0…5 kHz with 3 dB lowpass, unfiltered up to about 10 kHz
Ambient conditions for hot-wire probes
Fluid Air, other non-corrosive gases are possible but must be calibrated separately,
no particles, no air pollution
Temperature 10… 50°C within factory calibration, -10…70°C possible
Humidity Non-condensing
Measurement accuracy
Velocity 0…20 m/s 0.1 m/s + 0.5% v.M.
Velocity 20…50 m/s 1% FS (typ.)
Electrical parameters
Supply 9…18 V DC, min. 0.5 A, 10 W
Signal ±10 V
Headphone min. 32 Ohm
Supply / signal / enable Binder 711/712, 4 pin
Signal BNC
Hot-wire probe Binder 711, 2 pin
Headphones 3.5 mm audio jack
Ambient conditions for electronics
Temperature 5° C…40°C
Humidity Non-condensing
aCTA hot-wire bridge 150 mm x 56 mm x 24 mm
Ordering Options
aCTA 1x hot-wire bridge
1x power supply
aCTA-set 1x hot-wire bridge
1x power supply
1x headphone
2x hot-wire probes HWP10/xx at buyer’s option
1x carrying case