A measuring apparatus and method for use in measuring diffusible
hydrogen concentrations in materials, structures, and other objects. In an embodiment of the invention for use in
welding applications, the measuring apparatus (10) includes a sensor
assembly (20) that, with an included sealing member (40), defines a
sample area (17) on a
weld bead (16) from which
hydrogen evolves into a
sample volume (18) defined by the sealing member (40), a sensor housing (34) and a sensor (22) of the sensor
assembly (20). The
hydrogen reacts with a sensing layer (28) and a reflector layer (30) positioned on the end of an
optical fiber (24), all of which are included in the sensor
assembly (20) and are sealably positioned within the sensor (22). The sensing layer (28) comprises a chemochromic material that undergoes changes in physical properties, such as optical
transmission properties, when it reacts with hydrogen and these changes are measured by the measuring apparatus (10) to determine the amount of hydrogen evolving from the
sample area (17). An
optical fiber (46) is joined to the sensor
optical fiber (24) to direct light (63) transmitted by a
light source (62) in a hydrogen monitoring assembly (60) through the sensing layer (28) to strike the reflector layer (30) which reflects light (67) back through optical
fiber (46) to a
detector (68) in the hydrogen monitoring assembly (60). A
signal analyzer (72) is included in the hydrogen monitoring assembly (60) and is calibrated and configured to measure the diffusible
hydrogen concentration in the
weld bead (16) based on measured changes in the optical
transmission properties of the sensing layer (28).