Analog to digital conversion proved to be
problematic. Most of the sensors had
outputs in the order of millivolts and as
soon as the distance from the HESM was too
far, noise from the processor power supply
and AC interference at times exceeded the
signal levels from the sensors. This was
overcome through the use of buffers at the
sensors and current loop transmission.
Voltage t o frequency conversion with
RS-422 buffers to drive the digital
signals were investigated.