An electrochemical hydrogen meter using a CaCl2-CaH2 electrolyte and a Li-LiH reference electrode was constructed and used to monitor dissolved hydrogen in liquid sodium. These meters have been tested in bench-top sodium loops equipped with cold traps for controlling hydrogen levels in sodium. The experimental results showed that the meters yield nearly theoretical outputs down to the lowest hydrogen levels that were achievable in these loops (∼ 50 ppb). The sensitivity of the meters for changes in hydrogen concentrations is adequate for use in the sodium circuits of a fast reactor to detect leaks of hydrogen bearing extraneous materials into sodium. These meters, along with a gas chromatograph, were also used to study the reaction of hydrocarbon oil with liquid sodium. The experimental results showed that for detecting oil leaks into sodium these meters provide a simpler alternative to monitoring of methane in the cover gas using a gas chromatograph.