1IWF-EXP/ÖAW GRAZ

MP

Ele

ctr

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ics 2 Power budget

Interface electronics: ~1.5 W

Probe electronics (standby): ~1.2 W

Heater power: ~70 W

Power loss at tether3m 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)

2IWF-EXP/ÖAW GRAZ

MP

Ele

ctr

on

ics 2

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)

3IWF-EXP/ÖAW GRAZ

MP

Ele

ctr

on

ics 2

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)

4IWF-EXP/ÖAW GRAZ

MP

Ele

ctr

on

ics 2 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