Static Inclinometry with 'Spare' inclinometer on left A-frame

Summary
During the night of 981118/19 two static inclinometry measures were made covering a total of 13 hours. These were done with the spare inclinometer mounted next to the one on the left A-frame, and plugged into the channels that usually carry data from that on the right A-frame; i.e. two measures are made of the left A-frame. The L-eft and S-pare inclinometer data from the second (larger) dataset are shown below (with some additive constants for the sake of display) :

The variations in any data channel are due to either zero-point drifts, or to real tilts due to structural changes with time (temperature ?) :

• The antenna leg temperature system records a decrease in mean leg temperature from 4.3 degs C at 20:00 to 2.3 degs C at 09:00, although the inclinometer temperatures show total variation of only 0.2 degrees (they are plotted here at 10x their mV values, plus a constant offset for aethestics).
• The near-constancy of LY & SY implies minimal longitudinal tilting of the A-frame bottom beam with time or temperature, and/or minimal or similar zero-point drifts.
• The changes in LX & SX during this period are ~10" and of generally similar form, certainly in the latter half of the dataset, suggesting, in that period, real tilting of the beam in the X-direction, faithfully measured by each inclinometer.
• Explaining the differences between LX & SX in the first half of the dataset is harder . . .