Neutral pressure gauges of the ASDEX type (ASDEX pressure gauges or APGs) are an important diagnostic tool for monitoring particle exhaust in fusion reactors with magnetic confinement. To improve their performance under the challenging conditions of long-pulse operation, neutron irradiation, and high neutral pressures, alternative cathode materials have been investigated. This study focuses on the use of carbide cathodes–specifically hafnium carbide (HfC) and zirconium carbide (ZrC)–as thermionic emitters in APGs. We evaluated a Wendelstein 7-X-like and an ITER-like design. Stable operation is achieved with both designs, however the ITER-like design permits higher thermionic currents. Laboratory experiments have shown that carbides exhibit a much stronger interaction with hydrogen and helium compared to materials such as tungsten or lanthanum hexaboride, leading to a significant increase in the work function and a corresponding reduction in thermionic emission at high pressures. A pressure gauge with an indirectly heated ZrC cathode was also tested during plasma operation in the large helical device, where a gradual increase in heating current was observed. This effect was likely caused by shrinkage of the cathode’s carbon blocks, which limits the lifetime of the cathode unit to about 300 h in this unique case. The results demonstrate both the potential and the limitations of carbide cathodes for long-term use in fusion-relevant environments.