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Re: 11/4 SEDSAT Update(possible spurious data in current sensor



To All

I have been going through the telemetry from various people and have found the following anomaly.  The main current sensor occasionally comes up with the number 187611 as it is reading current.  This is a very strange number as it is outside the bounds of the A/D converter on the bird. (The conveter is an Analog Devices AD 7874 four channel 12 bit device which gives a range of -2048 to + 2047 hex in the range of -10 Vdc to + 10 Vdc).  Question to chris bond.  Would an erroneous number like that effect the software calculations of AMPS IN BATT?  I am nearly certain that this is not an artifact of transmission as this number only crops up in the current reading on the main sensor and no where else is it apparant.  I noticed this in the WOD file for either orbit 14 or 16 and also in the orbit 138 data gathered by one of the amateur radio operators.

If this is the case then a software filter will be needed that rejects any number outside the normal range of current readings.  Chris I don't remember but what is the max scale for the current reading.  If I remember it is 0.001 ohm resistor in series with the main current.  The resulting voltage drop is then amplified by a factor of 100.  If this is the case then the measure is 2 volts per amp with a max of five amps recordable.

Any ideas or has any of the AMSAT people seen similar things?

Dennis Wingo
KD4ETA


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