A 0.357-o.d. null-balanced pressure transducer was designed and built for 900°F at 350-psig service and tested on the bench for seven months at design conditions and 1200 and 1300°F at 350 psig until failure six weeks later. This type transducer was also tested in conjunction with a fuel irradiation experiment in the CP-5 research reactor. It provided experimentors with fission gas pressure readings until failure of the fuel pin.A unique device was used to control the reference gas pressure. Control was obtained by making use of the change in probe-disk electrical contact resistance. This method allowed the transducer to follow increasing and/or decreasing pressures easily and quickly as it took place. Transducers of this type generally operate on the probe, making and breaking contact with the disk which makes it easy to follow increasing pressure but becomes difficult to follow decreasing pressures.Resolution of the system was found to be±l/4 psig with an overall accuracy of±8 psig for full range.