Electronically scanned pressure measurement scanner for cryogenic wind tunnel applications

Electronically scanned pressure (ESP) measurement modules are used in wind tunnels to measure surface pressures on models. Measurement channels are connected to pressure ports through small diameter tubing. Use of current state-of-the art ESP scanners in cryogenic wind tunnels has led to several practical problems which contribute to additional expense and loss of data quality. First current use of ESP scanners in cryogenic wind tunnels (at room temperature to below -25/spl deg/ C) dictates the need for protection against the thermal environment. The current solution is the use of a heater box which causes a number of operational problems. The installation of the heater box is time-consuming and labor-intensive. Its size reduces the amount of space available for scanner installation. Secondly, a wind tunnel test must be interrupted for on-line calibration which consumes as much as 15% of the total test time. Finally, the pressure and balance measurements are taken in separate runs because of an "apparent strain" problem. An electronically scanned pressure measurement module capable of operating directly in a cryogenic environment has been developed and tested over an extended temperature span. Total uncertainty, which is measured at less than 0.1% of FSO at 1 atmospheric reference pressure will be discussed.