Abstract: A real-time recall feature for an engine data processor (20). An engine mounted data processor (20) inputs a plurality of engine operating parameters from a gas turbine engine (10). These parameters are fault checked and reformatted by the processor (20) before being output on a serial transmission channel (XCH) to an airframe mounted permanent recording apparatus (30). A set of the most recent engine profiles are stored in a dynamic random access memory (DRAM) which is constantly updated by overlaying the oldest data with the most recent. A switch (52) generates a signal (FRZ) to terminate storage of the profiles and freeze the contents of the (DRAM). The memory remains frozen having captured the most recent engine profiles associated with the generation time of the signal (FRZ) until unloaded over the channel (XCH) to recorder (30). The output of the (DRAM) is in response to a signal (RPL) generated by switch (52).

Abstract: A differential pressure measuring system is disclosed. The system includes two quartz capacitive pressure transducers (14, 16). Each capsule contains a pressure sensitive capacitor (Csa, Csb) and a relatively pressure invariable reference capacitor (Cra, Crb). The pressure sensitive capacitors (Csa, Csb) are excited by out-of-phase signals, (Vr, -Vr) which further excite the reference capacitors (Cra, Crb), out of phase, respectively. The outputs of all capacitors are combined in a summing junction (22) whose output controls the count of a digital integrator (34). A closed loop is formed by converting the output of the integrator (34) to a negative feedback signal (lf) which is applied to the summing junction (22) through a feedback capacitor (Cf). The integrator (34) incrementally changes the feedback signal (lf) in a direction to balance the loop. At this point the output of the integrator (34) is representative of the measured differential pressure.