A system and method for determining whether a hydrogen concentration sensor in the exhaust of a fuel cell system is operating properly during operation of the system. The protein named protein D is an Ig receptor for human IgD and has an apparent molecular weight of 42,000. The diffractive structures have concentric fringes centered near the slanted facet. The test modules are mounted in a pocket formed within the door for the test chamber such that the sensitive electronics of the modules are not exposed to the harsh environment within the test chamber, resulting in an exceptionally stable signal. A binary pixel value may be computed based at least in part on the first updated threshold value.