Td tensions after load cell calibration
The amplifiers for loadcells td4-1, td4-2, td8-1,
td8-2 were replaced on 02sep05 because the excitation voltage was 0 (the
voltage regulator chip was blown). After this,
the load cells for td4 and td 8 were calibrated. This was finished around
14:00 hours. The data from 14:00 to midnight was read in, averaged to 1
minute resolution and then plotted. The plots show
the tensions in the tiedowns after the calibration (.ps) (.pdf)
Fig1 top: The tiedown position vs hour of day. The colors are td12 , td4
, and td8.
Fig1 2nd: The tension in the individual cables
vs time. The solid line is cable 1 and the dashed line is cable 2. These
tension should be the same.
Fig1 3rd: The difference in the two cables at each
tiedown vs hour of day. After the calibration td4 cable 2 took about 1
hour to stabilize. There are jumps in the difference of up to 2 kips.
Fig1 4th: The difference in the two cables at each
tiedown vs the tension in a single cable. Td 4 has a slope versus tension.
This means that the gains for the two amplifiers of td 4 are not equal.
This is probably do to td4-2 since that was the one that was drifting around.
It should probably be recalibrated. With full scale of 80 kips=2.4 volts,
this is a drift of 4kips/80kips*2.4 = .12 volts over 30 kips.
Fig2 1-4: This is a blowup of Fig 1 from 14 to 17
hours. In panel 3 you can see the difference in td 4 changing for about
45 minutes after the calibration. Looking at panel 2 you can see
that it was the dashed line (cable2) that was changing. During this time
there was no tension on td4.