Abstract: A device for taking ultra-high frequency hydrometric measurements by generating sine wave trains of incident wave(s) at frequencies assuming several values in arithmetic progression between a few MHz and a few GHz, and has at least one ultra-high frequency cable. The cable includes at least two measuring stations (4) spaced along the cable a predetermined distance apart, each measuring station (4) having a measuring cell (14) and a separator device capable of only sampling a portion of the incident wave(s) with sufficient energy for each measuring cell to send back an echo measurable by electronic read-out device so that the sampling of the incident wave(s) by each measuring station occurs essentially simultaneously. Each measuring cell (14) consists of an ultra-high frequency line portion with its distal end terminated by a short circuit and with the line portion having a circumferential external wall which is either porous or provided with ports.

Abstract: A hydrometric sensor comprises a cable with a conducting core (1) surrounded by a dielectric sheath (2) which is interrupted at a succession of measurement stations (4), provided with a dielectric shield (6) with reduced section around which extends a volume filled with the test material. A portion of the signal enters this cavity, closed by a short circuited conducting ring (10) and which behaves as a resonant cavity in order to reflect a portion of the signal towards the source. The reflected signal is analyzed in order to infer from it the permittivity of the test material filling the cavity and therefore its humidity, as well as its temperature. A possible application is the monitoring of clays for confining used nuclear fuel.