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#300 by Zachstar on 15 Jun, 2007 03:25
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Final
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#301 by Chris Bergin on 15 Jun, 2007 03:28
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Article: http://www.nasaspaceflight.com/content/?cid=5135 - quotes all from L2, actually ended up not using many of them as the article became a bit too long as it is.
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#302 by noname_77065 on 15 Jun, 2007 03:31
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Good article, and good point about the media hyping the problems. They're using all kinds of ridiculous adjectives to describe the problems on orbit. Sad really.
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#303 by Zachstar on 15 Jun, 2007 03:32
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Power meter!
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#304 by Zachstar on 15 Jun, 2007 03:33
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The meter is moving all over the place. My guess is its cycling over several connections (some not connected)
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#305 by Zachstar on 15 Jun, 2007 03:34
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More images.
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#306 by Zachstar on 15 Jun, 2007 03:36
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Cable 4
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#307 by Zachstar on 15 Jun, 2007 03:38
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Going to cable 5 and 6
Reports no damage on the cables.
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#308 by Zachstar on 15 Jun, 2007 03:39
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Going to 5
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#309 by Zachstar on 15 Jun, 2007 03:41
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View of the connector of the meter
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#310 by Zachstar on 15 Jun, 2007 03:42
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Spooky!
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#311 by Zachstar on 15 Jun, 2007 03:44
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Suni reports this one looks different.
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#312 by Zachstar on 15 Jun, 2007 03:45
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"Input A range victor"
Command they want her to enter into it. -
#313 by Lee Jay on 15 Jun, 2007 03:47
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Why are they looking at currents? The source controls the voltage, the load controls the current. Well, unless this is a current-source power system (no way).
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#314 by Andrewwski on 15 Jun, 2007 03:49
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Are they definitely looking at currents or are they looking at frequencies?
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#315 by Launch Fan on 15 Jun, 2007 03:50
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Or this, from Chris' new article:
'It appears the computers are sensitive to noise. Problems occurred when the truss was attached,' added another note. 'It's possible that the ground path changed with the addition of the truss, which increased the noise level. There will be some troubleshooting later today. The crew will use a scope meter to check for noise.'
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#316 by JWag on 15 Jun, 2007 03:53
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Quote
Lee Jay - 14/6/2007 10:47 PM Why are they looking at currents? The source controls the voltage, the load controls the current. Well, unless this is a current-source power system (no way).
To some extent, the current will be proportional to voltage, so looking at currents can give an idea about noise.
They're using a clamp-on inductive probe on the meter. There may not be available testpoints to look at voltage (and they're not going to be disconnecting things or piercing insulation), so monitoring current is the next best thing.
Edit: I don't know anything specific about the ISS power delivery. It looks as if the solar panel electricity is converted to AC for transmission down the trusses, so clamping a lead around the power cables heading to the computers would give an indication of the current drawn by those boxes.
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#317 by MKremer on 15 Jun, 2007 03:58
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Seems rather unusual a location wasn't designed in from the start (or better, locations) with capped test points for power tests like they're doing now. Did all the designers actually think an on-orbit crew would *never* have to test power or current problems throughout the station construction and lifetime??
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#318 by Zachstar on 15 Jun, 2007 04:02
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On to cable 6
Change scale up
Good batteries even tho you see the battery symbol.
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#319 by Lee Jay on 15 Jun, 2007 04:04
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Unless they're monitoring ground current, I would think looking at currents would be totally misleading unless they suspect the loads (computers) at the source of the problem. It could also be that I don't know where in the circuit they are looking. Perhaps they are looking at power converter input currents or paired cable with common-mode noise.
I suspect you're right that they just don't have available test points and they're getting what they can get easily. I have a good deal of experience dealing with noise problems since I use sensitive instrumentation in extremely noisy electrical environments (way more power, voltage, and EMI than ISS), and I haven't had success with this approach. Problems like this for me have always come down to a problem with grounding and shielding - ground loops, multiple grounds at different voltages, open shields, shields with multiple tie points etc. I'll often do this sort of test with a hall-effect current probe on a ground, but not on a main cable unless I suspect a common-mode problem of some sort (rare).