Constant Temperature Anemometry (CTA)
Constant Temperature Anemometry (CTA), also known as Thermal Anemometry, is a technique for the measurement of turbulence in 1D, 2D, or 3D flows using hot-wire or hot-film probes inserted into the flow.
The working principle is based on the cooling effect of a flow on a heated body. The CTA measures velocity at a point and provides continuous velocity time series, which can be processed into amplitude and time-domain statistics.
The CTA box has to be connected to the hot-wire probes through a special support.
The CTA boxes available at the lab are listed below:
- Multichannel CTA 54N82 with 4 MiniCTA 54T42 channels
- Multichannel CTA 54N81 with 6 MiniCTA 54T42 channels
More information can be found in the following files MiniCTA main specs
Note: The CTA box has to be set before use through the following Excel sheet CTA setting. The inputs needed are the listed below:
- Sensor resistance in Ohm;
- Lead, support and cable resistances(these values are usually constant);
- Current temperature of the flow;
- Desired temperature of the sensor, which will influence the overheat ratio. Note: Do not exceed 350 degrees Celsius .
- Length of the cable (in m). Note: It is recommended to use short cables.
The Excel sheet will provide the configuration of the switches for the MiniCta. Note: This operation has to be repeated each time prior the use of the sensors.
Each miniCTA has 7 sleeves from J1 to J8. The sleeves that have to be on are J2 and J3, meaning offset off and gain off, respectively.One sleeve has to be on either J5,J6,J7 or J8, depending if we want to apply the signal filtering at 1kHz, 3kHz, 10kHz or no filter, respectively. All this information is sketched on the bottom of the lid of each multichannel CTA.
Note: Each Multichannel CTA has to be grounded.