The Art of Encoding a PCM Telemetry Stream: Interweaving Pre-Recorded and Live Analog/Digital Sensor Data in Gun-Launched Instrumentation Systems

Abstract

Typical Telemetry applications can be easily resolved using Inter-Range Instrumentation Group (IRIG) 106 Chapter 4 (Pulse Code Modulation [PCM] Standards) where live data can be immediately transmitted at a periodic rate for all sensors on board. However, issues arise when multiple high sampling rate channels are required during a gun-launched in-bore event where transmission is impossible. Further complications are added if using a sensor suite consisting of a mix of digital sensors with fixed Output Data Rates (ODR) and analog sensors allowing control over the sampling period. To overcome these issues, the Telemetry Branch at Picatinny Arsenal has developed custom electronics and firmware to handle the unique projectile instrumentation applications required to gather data from both in-bore gun-launched environments and in-flight dynamics before the telemeter is destroyed upon impact. This paper will dive deep into how the Telemetry Branch has handled the intricacies of telemetry frame building in the application by double buffering mixed signal sensor data in the firmware code.