Towards a fully autonomous mini-ams (for UT/LMS measurements within the CARIBIC project)

Transcription

1 Towards a fully autonomous mini-ams (for UT/LMS measurements within the CARIBIC project) CARIBIC = Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container , Florian Rubach

2 The CARIBIC project In operation since 2001, flights ~monthly freight container with instruments installed into the cargo bay of an A passenger aircraft Operates for a set of four regular intercontinental flights Air is sampled through permanently installed inlet on belly of the aircraft Instruments to measure CO2, CO, O3, NO, NO2, NO y, CH 4, Hg MAX-DOAS, PTRMS, OPC, several CPC s, aerosol sampler, SP2, sophisticated whole air sampling system for GC analysis Unique, long-term dataset for the UT/LMS region Details in Brenninkmeijer et. al., 1999,

3 Requirements posed by the project Electrical Power supply from 24 VDC, 20A max Instrument needs to live with power cuts Power available only short time before flight Cables need to comply with safety regulations EMI compatibility Physical Fit in 19 Rack, weight as low as possible Withstand 9 g acceleration to front and down, 3 g all other sides Operating temperatures may be above 30 C Technical Wide range of ambient pressures No operator - 3 -

4 Electrical Cables (including HV) replaced by flame retardant versions, PVC-free Installed micro UPS (~1 kg) allowing safe shutdowns on power cut Installed car PC power supply running off 24 VDC into computer Removed 230/110 VAC 24VDC converter in TPS, installed 24VDC 12VDC converter Removed converters from Giraff, new housing with less card spacing and better cooling, half the size, houses extra electronics (Chopper) - 4 -

5 Physical Profile extrusion frame Individual component fixation Improved pump cooling < 80 kg, 70 cm high 19 Rack unit - 5 -

6 Physical old new new old - 6 -

7 Technical Wide range of ambient pressures New type of pressure controlled inlet (constant lens pressure) integrated into new inlet No operator, no remote access Automate startup, shutdown, filter sampling + SI calibration (*) Software clicks buttons in Joels DAQ, scriptable Restart in case of software failure (*) Removed all necessities for physical interaction Automated all valves Replaced eptof electronics (*) work in progress

8 eptof Disclaimer: eptof in its current state SPECTACULARLY outperforms regular PToF, both in terms of signal intensity and size resolution - 8 -

9 eptof: Why we need improvements Ideal operation: MS extractions aligned with the segments seen by the particle beam within one rotation Frequency lock, phase lock MS pulser period adjustable in steps of 0.05 µs, chopper rotation set in integer Hz (limitation of the BLDC motor control chip) mismatch is almost unavoidable If acquisition of desired set of MS takes longer than a full revolution, DAQ will skip a cycle 50% duty cycle! BLDC chip PID-controls chopper rotation speed rotation speed oscillates, same order of magnitude as pulser period! Reflex optosensor has focus distance of ~2 cm very broad peak for slit, good for speed measurement, not suitable for edge detection Asymmetric holes in disc center of gravity center of rotation (~0.2 mm), bad vibrations! CARIBIC specific issue: no operator no one to push button to start rotation - 9 -

10 eptof: The way to go Reflex optosensor with 1 mm focus distance more precision 86 mg and 66 mg of weight (washers) added to two chopper wheel mounting holes much smoother rotation Tee off signal going into pulser, feed it into eptof control electronics Make oversampling factor n and pulser period τ known to control electronics expect n 127 MS pulses per revolution, rotation period is n 127 τ As default, spin chopper at calculated rotation period When in PToF mode, use MS pulse signal as clock to drive rotation of the BLDC motor As DAQ waits for first optosensor slit signal, we are now by definition phase-locked Due to inertia and differences in ADQ1600/AP240 and electronics timing, frequency lock might take a few rotations To make sure no data is thrown away, one could reduce the rotation period by a fraction of τ

11 Thanks for your Attention! Max-Planck-Institut für Chemie Hahn-Meitner-Weg Mainz