1IWF-EXP/ÖAW GRAZ

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Mass w/o electronics

Calculated: 450g

Measured: 350g, 3m tether

Main Components

Cable cartridgeContains the tether and the slip-ring mechanism

BodyContains the MP electronics and provides space for the payload

TipContains front heater and provides space for optional vibration system

Melting Probe V2.0 Mechanics

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The Tip

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Space for MP electronics and payload

Relatively large openings for installation of MP electronics and payload (18 x 31mm)

Water tight interface to the tip and the cable cartridge

The Main Body

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Enough space to contain more than 10m of tether

Slip-ring mechanism with water tight cover

System to measure the vertical position of the probe

Water tight interface to the main body

The Cable Cartridge

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All mechanical parts available

Manufacturing quality is good, price was reasonable

All parts have been pre-assembled

Minor changes have been applied during the assembly process

Additional openings for heater and sensor harness

Cut-outs in the tip for Pt1000 and harness

Adjustment of slip-ring contacts

Tests with cable cartridge

Slip-ring test

Cable pull-out test

Summary and Tests

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Assembly of slip-ring is critical: balance between friction for cable pull-out and spring load to electrical contacts

Test:

Slip-ring assembled without tether

Applied current 3A per signal line

Contact voltage measured

Slip-ring failed after ~4500 turns

Slip-ring Test (1/2)

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Test was performed in steps: 1000, 1000, 1000, 7000

After each stip slip-ring was dismantled and images were taken

Slip-ring Test (2/2)

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Test set-up

Cartridge fully assembled with slip-ring and tether

Cartridge fixed at the bottom; actuator was used to pull out the cable (0.5 mm/sec, 1.3 mm/sec)

Load cell was used to measure the force applied to the tether

Necessary force is low and results repeatable

Cable Pull-out Test

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Status

More changes than foreseen for this phase

Circuit diagrams ready

Layout of prototyping board started

Functionality of prototyping board

Electrically identical with final MP electronics (MPE V3)

For cost reasons standard PCB technology used

All heaters, sensor, mechanisms and communication will be checked before final PCB in rigid-flex technology is ordered

Reference model for the update of the interface unit and the control software

Electronics Design (1/2)

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Electronics Design (2/2)

Placement and Layout

All passive SMD components changed to 0805 size

Both sides of the board will be populated

Available space is still critical

Power module shall be separated from measurement and communication module

Connector type OMNETICS mounted directly onto flex board

Largest component is the DC/DC converter

DC/DC

Max

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PCB rigidPCB flex

Shield connected to GND (copper with Kapton)

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Power and Grounding Concept

Power electronics galvanically disconnected from control electronics

All power devices, heater and motor, at primary ground

Control and measurement devices at secondary ground

Communication channel connected to +28V lines only

Interference from DC/DC converter to communication is minimised

DC/DC converter with dual supply output

Melting Probe Electronics (V2)

DC/DCConverter

CommunicationModule

5V

28V

GND

Melting Probe Electronics

+5V

RX

TX

28V Nom.

28V Red.

RET Nom.

RET Red.

-5V

Heater

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Same processor type, but latest version with 12bit ADC will be used

Thirteen analogue channels used

In total seven heater control units (5 + 1 + 1)

Accelerometer with three axis (analogue output)

Temperature reference with AD590 (1µA/K)

Voltage reference for corrections

Monitoring of 28V supply

Additional signal lines

In- and output for position measurement

PWM output with opto-coupled FET @ 28V for motor control

Processor

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Heater control line is galvanically isolated

Opto-coupler for isolation

FET with +5V control input, current limiter and thermal control

Temperature measurement

Change to Pt1000

Current source with 1mA

Two wire interface

Instrumentationamplifier with dual supply

Heater Control

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Three axis accelerometer ADXL330

Range ±3g

Analogue output typically 300mV/g

Additional amplifier to increase sensitivity

Change from two axis to three axis sensor to support direct mounting at the PCB

Probe Orientation

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Infrared LED activated by processor

Opto-transistor as sensor

Cut-out in track is not sufficient, since absorption of Kapton foil is too high

Next version of tether shall provide cut outs through all layers

LED only activated when signal from opto-transistor is sensed

Position Measurement

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Serial, full duplex, carrier frequency based communication, similar as used for MPE V2.0

Signal is now transmitted as differential signal, via +28V-Nominal and +28V-Redundant line

Noise of DC/DC converter is not seen by communication signal

Improved filter designs

All OpAmps with dual supply

Input filter identical with MPE V2.0, but improved design for signal reconstruction

Simulation showed larger separation

Coding for new version is inverted, logic “1” activates carrier

Communication

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Transmitter

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Receiver

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Simulation Results

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Installation of heater, Pt1000 and harness

MP Electronics

Layout, assembly and board level test of prototype

Layout and assembly of final MPE

MPE Software

Adoption of MPE software and communication protocol to new sensor configuration

Additional control routine for motor PWM

Interface/Surface Unit

Population of another board (differential signals)

Adoption of interface module software

EGSE Software

Adoption to new sensor configuration

Update of data correction routines

Tasks still to be Finished