MP Electronics 2 1IWF-EXP/ÖAW GRAZ  Power budget  Interface electronics: ~1.5 W  Probe electronics (standby): ~1.2 W  Heater power:~70 W  Power loss at tether 3m and max. heater power:~10 W  Suggestion  For safety reasons: the present design shall be kept (laboratory model)  The design for a real flight unit shall be based on a supply voltage of a few hundred volts (limitation due to cable and connector) Known Problems with MPE1 (1/3)

MP Electronics 2 2IWF-EXP/ÖAW GRAZ  Communication  The existing design is based on a carrier frequency  The signal is capacitively coupled to +28V and Return  DC-DC converter for the probe electronics and the voltage drop due to the switching of heaters create a high noise level  Filtering practically not feasible (available space)  Suggestion  Direct connection from GND to Return shall be avoided (heater control via opto-coupler)  Use of differential signals for driver and receiver  Make use of redundant lines for 28V Known Problems with MPE1 (2/3)

MP Electronics 2 3IWF-EXP/ÖAW GRAZ  Temperature Measurement  Pt100 have been used for temperature measurement  Supply current was 1mA (self-heating?)  4-wire interface necessary to achieve accuracy, but harness needs large space  Suggestion  Change to Pt1000 and 0.1mA supply current  Use of 2-wire interface will introduce only small error  Use of symmetric supply voltage to facilitate signal conditioning (improves the situation with the communication circuitry too)  Change to connectors from Omnetics to save place Known Problems with MPE1 (3/3)

MP Electronics 2 4IWF-EXP/ÖAW GRAZ  Mechanical design  New mechanics provide rectangular shape space  PCB will be realised in rigid-flex technology  Populated PCB will be folded to a stack of 34 x 60 mm PCBs  Part of the harness to Pt1000 and heater will be realised as flex-board  Electronics design  Part of the suggested design changes will be implemented onto the “old fashion” MPE1 to be tested  Galvanic de-coupling between heater and control electronics (no common ground)  Software design (probe electronics, interface, PC driver)  Presently no problems known therefore no changes foreseen Proposed Design Changes for MPE2