project:hgg:open_tasks:sensor:testing:manual_cable_trigger_for_runtime_measurement
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project:hgg:open_tasks:sensor:testing:manual_cable_trigger_for_runtime_measurement [2012-01-11 14:32] – angelegt 87.180.39.132 | project:hgg:open_tasks:sensor:testing:manual_cable_trigger_for_runtime_measurement [2012-01-11 16:03] (aktuell) – 84.56.144.91 | ||
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The signal runtime of each cable has to be calculated or measured, so that an ordinary pushbutton can be used to trigger all 4 events and one doesn' | The signal runtime of each cable has to be calculated or measured, so that an ordinary pushbutton can be used to trigger all 4 events and one doesn' | ||
If an arduino is capable of measuring runtimes in cables of 2m looping from and back to an arduino, this can be used instead of calculations. More informations are needed. | If an arduino is capable of measuring runtimes in cables of 2m looping from and back to an arduino, this can be used instead of calculations. More informations are needed. | ||
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+ | Cable propagation speed of signals is given by the formula as shown in http:// | ||
+ | To calculate the speed, you need the relative dielectrical constant (permittivity) of the insulating material of the cable, which is 2.4 for polyethylene. So, the speed of signals in a PP insulated wire is 1/SQRT(2.4) = 0.65 times the speed of light = 200,000 km/s. | ||
+ | The relative permeability can be assumed to be 1 in this equation. | ||
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+ | Practically, | ||
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+ | For real measurement you need a high speed counter, running at about 200 MHz. This could be done with a fast PLD or FPGA with any microcontroller for display. A simple uC with 10 MHz clock won't work with sufficient precision. |
project/hgg/open_tasks/sensor/testing/manual_cable_trigger_for_runtime_measurement.1326288759.txt.gz · Zuletzt geändert: 2012-01-11 14:32 von 87.180.39.132