5 ms·

Reminds me of a large particle physics experiment I worked on. One of the detectors had a critical flaw, IIRC the output voltage of the detector modules was pro

Reminds me of a large particle physics experiment I worked on. One of the detectors had a critical flaw, IIRC the output voltage of the detector modules was proportional to the number of particles passing through it. At every readout, it was reset to 0. Now, if you didn't read out the modules often enough (every few seconds), they would fry themselves. The problem wasn't noticed until the readout system crashed and a couple of modules were destroyed. When the bug was presented in a meeting, there was one guy who insisted that we install a big red button to shutdown the system. There was even discussion on whether it should have a little lid or not. When that guy left the meeting early, they briefly considered to install a fake button. In the end, what happened is that they built a "heartbeat" system that just zeros out the modules every second or so. The information in the modules is lost, but since there are millions of collisions each second, this had virtually no impact on data taking. But it prevented damage when the readout system crashed again. They also made a little GUI in the control room showing a beating heart probably just to calm people down :-).

antognini 12y ago
Interesting. I've observed at a number of telescopes and they all have a big red STOP button that will shut down the telescope immediately. I've only had to use it once. The telescope was poorly designed and it was possible to run it into its hard limit (you could basically run it into the ground). If you do that you have to stop it because the tracking motors will continue to try to drive the telescope into the ground. The only exception was the Large Binocular Telescope, which is one of the largest telescopes around (even the largest, depending on how you define it). But there a lot more thought was put into the design so you wouldn't be able to run the telescope into the ground even if you tried. (It also helps that they have a dedicated night assistant whose job it is to point the telescope and make sure that the observers don't do anything stupid.)

antognini 12y ago

Interesting. I've observed at a number of telescopes and they all have a big red STOP button that will shut down the telescope immediately. I've only had to use it once. The telescope was poorly designed and it was possible to run it into its hard limit (you could basically run it into the ground). If you do that you have to stop it because the tracking motors will continue to try to drive the telescope into the ground. The only exception was the Large Binocular Telescope, which is one of the largest telescopes around (even the largest, depending on how you define it). But there a lot more thought was put into the design so you wouldn't be able to run the telescope into the ground even if you tried. (It also helps that they have a dedicated night assistant whose job it is to point the telescope and make sure that the observers don't do anything stupid.)