A diagnostic method and associated test kit for detecting an analyte residing in a test sample is provided. The mounting provides a non-elastomeric snap-together bushing formed of a plastics material which accurately positionally locates the sensor or emitter with respect to its mounting while providing an unexpectedly high degree of isolation with respect to transmission of acoustic and other energy forms through the mounting. If a predetermined period of time elapses while the clutch lever L is not operated, then the shifting request is an erroneous operation and the shift stage is returned to an original gear. Methods and apparatus for independent control of electron emission current and x-ray energy in x-ray tubes are also provided.