Abstract: Apparatus and associated methods relate to an accelerometer having first and second piezoelectric transducers that are electrically isolated but mechanically coupled one to another via a coupling member. The first piezoelectric transducer is configured to induce a mechanical deformation of the coupling member in response to an electrical excitation signal received by the first piezoelectric transducer. The second piezoelectric transducer is configured to generate an electrical response signal in response to mechanical deformation of the coupling member. The accelerometer has a self-test module configured to generate the electrical excitation signal and to receive the electrical response signal. The self-test module is further configured to generate a sensor test result based upon a comparison between the received electrical response signal and a reference signal. The self-test module may advantageously detect changes in an excitation/response relation due to time and/or environmental conditions, for example.

Abstract: Techniques for monitoring the magnitudes of representative filtered EGM signals over time. In a typical implementation, a group of digital peak values is generated in a time period and a representative digital peak value is selected for the time period. By comparing representative peak values for several time periods, changes in signal efficacy can be identified.

Abstract: The invention presents techniques for monitoring the magnitudes of representative filtered EGM signals over time. In a typical implementation, a group of digital peak values is generated in a time period and a representative digital peak value is selected for the time period. By comparing representative peak values for several time periods, changes in signal efficacy can be identified.

Abstract: A pressure relief valve assembly has a tubular body (10) with an internally projecting first valve seat (34, 80). An annular seal carrier (22) supports a resilient seal (24) which is spring-biased into engagement with the first valve seat (34). A movable valve member (44) has a second valve seat (46) which is spring-biased into engagement with the resilient seal (24), the range of movement of the movable valve member (44) towards the resilient seal (24) being limited by an abutment formation (52) which engages with a complementary formation (54) on the body (10). The resilient seal (24) comprises a body portion (26) abutting the seal carrier (22), a first lip portion (32) capable of flexing movement relative to the body portion (26) and adapted to engage with the first valve seat (34) and a second lip portion (48) capable of flexing movement relative to the body portion (26) and adapted to engage with the second valve seat (46).

Abstract: An apparatus for and method of measuring the current which flows through a cardiac pacing lead to artificially stimulate contractions of the myocardium. This current measurement is useful for estimating battery life and monitoring proper operation of the pacing lead and the implantable pulse generator.The measurement is accomplished by carefully controlling the gain of the output amplifier and timing the rate of charge and discharge of the output capacitor. The average pacing current can be determined from the relative charge and discharge times given that the other circuit component values are known and controlled.