With Terrence.

With the aim of centering the IP we did preparatory work.

The motors may jam when reaching the very end of its moving range and we want to avoid this by keep track of their positions as much much as possible. In the case of the SR3 IP there were no consistent records of their position in number of steps, therefore, we did some measurements before using them to adjust the IP. The steps we follow are:

• We locked the IP in order to checked the LVDT read out at nominal position. This is done in the following order: lock near LVDT #1, then #2 and #3. This means from #1 to #3 counterclockwise. (See medm centering screen).
  • LVDT #1: -221 µm.
  • LVDT #2: -103 µm.
  • LVDT #3: -297 µm.
  • Longitudinal: -55 µm.
  • Transverse: 98 µm.
  • Yaw: -349 µrad.
• We released the IP. Its position was
  • H1: -2474 µm.
  • H2: -2624µm.
  • H3: -2191 µm.
  • Longitudinal: 82 µm.
  • Transverse: -212 µm.
  • Yaw: -4091 µrad.
• The position of the stepper motors were:
  • H1: -200,000 steps.
  • H2: 0 steps.
  • H3: -600,000 steps.
• We moved H3 motor to one end and then to the opposite end:
  • Maximum: 1,600,000 steps.
  • Minimum: -2,500,000 steps.
  • Total range: 4,100,000 steps = TR
  • Position at the physical centre of the assembly: -150,000 steps. We determined the position by visual inspection (counting holes in a component).
  • D_plus = 1,980,000 steps.
  • D_minus = -2,120,000 steps.
  • Mid-point of the stepper motor range: -450,000 steps (note the notebook is wrong).
• We moved the remaining motors to their respective physical mid-point of the assembly.

In summary

Total range: 4,100,000 steps.

Mid-point from either end: 2,050,000 steps = TR / 2 .

Please note the table in the notebook is wrong because I used TR / 2 instead of the D_plus and D_minus.

When the motors were centered the IP was misaligned. The next step was to align it with the jacks, task which is reported in a separate entry.