The goal is to measure the H angle between the segment joining the fiducials of the 2 scanners of the bench in their "survey" position, and the normal to the autocollimation mirror associated with this bench. The procedure is the same for both benches, except that: -the upstream one needs a BSY access, the downstream one just a Hall A access, providing the light tubes were left in straight position.
-the upstream angle is 
0, only affected by a change in the scanners;
the downstream one is 6 deg and it can be affected by a change in
the scanners or by a motion of the tunnel.
-the upstream autocollimation is at short distance, the downstream one is at long distance, through the light tubes, and the line of sight is bent by a pair of mirrors, both at forward and at backward pass.
The procedure is:
-using the "expert task" (see detail), set both scanners in their "survey" position (encoder=118407+-2)
-install the theodolite on its support and level it carefully.
-mount the battery (2 autocollimation batteries and chargers are stored in the shed, make sure the batteries are charged)
-push the "ON/Enter" button, the bottom display prompts "V zero 1"
-release the "V" break (small knob of the top pair of knobs)
-initialize the V (Vertical angle) encoder by turning slowly and continuously the optics around the horiz. axis in a direction, until you get a beep and "V zero 2" displayed. Then turn in the opposite direction, until you get a beep and "A zero" displayed in the top display.
-release the "A" break (small knob of the bottom pair of knobs)
-initialize the A (Horizontal angle) encoder by turning slowly and continuously the whole theodolite around its vertical axis, until you get a beep and "Theo" displayed in the top display. Push "ON/Enter" button to accept the proposed "theodolite" menu.
-from this point, "V" and "A" angles will be permanently displayed in their own displays, in units of decimal degrees from 0.0000 to 359.9999 If the decimal part is not displayed, correct the levelling.
Note: the origin of the A angles is arbitrary (this is not the case for the V angles), so you may decide to set it to zero, for example at the first autocollimation measurement: this way, the measured angles will be more intuitive. To do this:
-from the "THEOD" menu push on "+" (means go to the next menu called "SET A")
-"SET A" menu is proposed: push "enter" to accept, you have a "WAIT" displayed, after which the angles are displayed again, but with A=0.0000.
-push "-" to proceed: the sub-menu "MEAS P" is proposed, you must accept ("enter"), you have then the angles displayed, push "-" to come back to the "THEOD" menu, then push "enter" to accept it, you should still have A=0.0000: you have a new origin of the A angles.
-measure the autocollimation angle:
-open the light tube
-plug the autocollimation light cable
-turn ON the autocollimation power switch on the battery
-adjust the autocollimation power potentiometer to half range
-remove the theodolite handle, to let the cable go through.
-adjust the occular (small knob on the optics) to your vision, until you have the cross hairs well focused
-adjust the main focusing (large knob on the optics) to infinity (turn counter
clockwise up to the limit and come back by 1/4 turn)
-adjust the V angle to 90.00?? deg.: first move the optics, second fasten the V break and use the V knob.
-adjust the A angle to point in the direction of the light tube: first move the theodolite, second fasten the A break and use the A knob.
-using the A knob, search for a light signal
-focus on it (main focusing): the autocollimation pattern is a yellow/green cross
-adjust A and V angles to get the cross hairs on the autocollimation cross, fine adjust both focusings, then check if the pattern you have is the good one (there are 2 wrong autocollimation patterns): when you change by a small amount the A/V angle, then the A/V coincidence between both crosses must be destroyed. If it is not the case, you are focusing on one of the two wrong patterns. Then change the main focusing towards infinity (counter clockwise) to get another patern.
-fine adjust the autocollimation power potentiometer to get the best vertical line of the autocollimation cross -fine adjust A and V angles, record their values in the Shed logbook.
-change both angles by 180.000 deg., WITHOUT CHANGING THE MAIN FOCUSING, and redo the previous step.
-close the light tube
-turn OFF the autocollimation power switch on the battery, Note: the above measurement is easy from upstream, more tricky from downstream (long distance autocollimation). New operators should start with the upstream measurement.
-measure the scanner #2/#3 (the one which is on the autocollimation side)
-remove the scanner cover -unplug the connexion of the encoder to the VME -plug the control box on the fiducial lamp and on the encoder
-record the encoder reading in the logbook. It should be 118407+-2
-adjust the main focusing on the fiducial wire
-adjust the V angle to the middle of the aperture across which the wire appears -fine adjust the A angle, record A and V values in the Shed logbook.
-change both angles by 180.000 deg., WITHOUT CHANGING THE MAIN FOCUSING, and redo the previous step.
-record the encoder reading in the logbook. It should give the previous reading +-1 encoder unit
-unplug the control box
-plug the connexion of the encoder to the VME
-cover the scanner, Note: in case of scanner #2, a foil closing the apertures in the mirror support must de removed prior to the survey, and reinstalled after.
-measure the scanner #1/#4 as for #2/#3
-re-measure the autocollimation angle.
-turn OFF the theodolite (push simultaneously the + and - buttons)
-release both breaks
-mount the handle
-dismount the theodolite
-dismount the battery and the autocollimation cable
-store the theodolite in its box
-store the theodolite box and the control box in the Shed
-charge the battery(ies)
Note: in case you have to change the battery during the measurement, redo the
complete measurement with the new battery. A battery in good shape can provide
2h of work with autocollimation ON. The survey of
a bench will take between 1h and 1/2h. If possible, discharge the battery before
charging it.
-analyze the angle:
-in the directory gougnaud/arc2/ARC/angles, edit a plain ASCII file
named upstream_ddmmyy.dat or downstream_ddmmyy.dat, depending on the bench,
where ddmmyy stands for the date of the survey. Use upstream_270798.dat or
downstream_270798.dat as a model. Units are encoder unit and decimal degrees.
If several measurements of the same quantity were done, enter the average. If
the full measurement of a bench was done twice, edit both sets of data as in
the model.
-run "angle" on a Sun machine and follow the instructions
of the program, accept the proposed mirror calibration angle and ask for an
average of all your measurements. If only one bench was measured (encoder change,
BSY closed,...), use for the other bench the most recent file available in gougnaud/arc2/ARC/angles.
-analyze individual measurements and compare them to the above average. The
reproducibility of the reference angle measures several times on the same day
should be 
10-3 deg (17 urad 3 10-5 on the energy).
-compare the new average to the previous one: if nothing changed in the scanners, and if only the downstream angle changed, this can be interpreted as a motion of the arc (the code gives the detail of the 3 angles: upstream, downstream and reference).
-the files used today (01/07/99) are upstream_250699.dat (1 meas.) and downstream_250699.dat (2 meas.). They result in a reference angle of 34.32322 deg. (averaged)
-write the new reference angle in the arc-scan source code (include file "arc-incl-plot.f", parameter "Reference_Angle_Degree")
-compile and test the arc-scan code.
-report in the e-logbook about the changes and results (file names).
Example of upstream file: upstream_250699.dat (1 meas.)
UPSTREAM BENCH MEASUREMENT
**************************
Used unit: decimal degrees
Enter data in this order:
- Horizontal Distance (point A, down. fiducial)= 1975.00 mm #2
**********************
25/06/99 Andrew+Tim Mesur. Nb 1
First measurement on 25/06
Encoder reading for upstream scanner of upstream bench: 118406 #1
Encoder reading for downstream scanner of upstream bench: 118406 #2
| H1 | H2 | V1 | V2 | |
| 0.000100 | 179.995500 | 90.002100 | 270.003500 | Autocoll. |
| 359.977700 | 179.973900 | 250.509900 | 109.498800 | #1 |
| 179.970000 | 359.967100 | 250.382500 | 109.619700 | #2 |
Example of downstream file: downstream_210699.dat (2 meas.)
DOWNSTREAM BENCH MEASUREMENT
****************************
Used unit: decimal degrees
Enter data in this order:
- Horizontal Distance (point A, up. fiducial)= 1870.00 mm #3
- Horizontal Distance (point A, down. fiducial)= 1840.00 mm #4
*********************
21/06/99 Pascal Mesur. Nb 1
First measurement on 21/06
Encoder reading for upstream scanner of downstream bench: 118405 #3
Encoder reading for downstream scanner of down. bench: 118408 #4
| H1 | H2 | V1 | V2 | |
| 0.000100 | 179.998050 | 90.001400 | 270.000000 | Autocoll |
| 6.100100 | 186.10110 | 110.667500 | 249.336900 | #3 |
| 6.176100 | 186.175700 | 249.129900 | 110.876300 | #4 |
*********************
21/06/99 Pascal Mesur. Nb 2
Second measurement on 21/06
Encoder reading for upstream scanner of downstream bench: 118405 #3
Encoder reading for downstream scanner of down. bench: 118408 #4
| H1 | H2 | V1 | V2 | |
| 0.000100 | 179.998100 | 90.003800 | 270.003000 | Autocoll. |
| 6.100800 | 186.100400 | 110.667600 | 249.338500 | #3 |
| 6.176000 | 186.176100 | 249.130700 | 110.875600 | #4 |