The 56C01 CTA contains a function switch with three modes for operation, namely TEMP, STD.BY and FLOW. In TEMP position the resistance of the connected probe can be measured in terms of a current supplied to it. In STD.BY position no current flows through the bridge. In FLOW setting the CTA starts operating with the function of the servo amplifier. If the function switch is shifted quickly from position TEMP to FLOW, the square-wave generator is activated. A setting named BRIDGE ADJ enables the adjustment of bridge balance for measurement of probe resistance and setting of the desired overheat resistance. BRIDGE ADJ has a switch pair for coarser adjustment of overheat resistance and a screw for  fine adjustment. Resistance settings ranging from 0-30 in steps of 0.001 are possible. This adjustment is crucial for adjusting the overheat resistance for the calibration procedure. CTA in TEMP mode produces a voltage proportional to resistance of wire. From the wire resistance, the instantaneous temperature attained by the wire at a given location in the flow field can be determined.

The main-frame of the anemometer unit is fitted with the 56N20 signal conditioner unit, which is designed to amplify the AC signals up to a level suitable for PC-based data acquisition. The signal conditioner can selectively amplify the input signals with gain factors ranging from 1 to 900. The filter circuit comprises high-pass and low-pass  filters as well as an amplifier. The filter settings were determined in the present work by examining the complete power spectrum of the velocity components. For the present investigations, voltage signals from the CTA were low-pass filtered at 3.0 kHz and highpass filtered at 0.1 Hz. The mean-value unit 56N22 is a 5.5 digit display voltmeter, and the primary purpose of this module is to measure the DC component of the output signal from 56C01 CTA. This module has a resolution, 1-1000 seconds integration time and switch selectable 14 inputs.