Servo System Adjustments

Periodic adjustments are necessary to ensure that no offsets are added to the servo system. To do this, follow these instructions:
 

CAMAC Multidac 9085 (or HYTEC 640VSL)

  1. In initialised state (all channels OFF) check outputs of channels 0 to 3 are ZERO.
  2. Overwrite channels 0 to 3 with 2048 (bit 12 set) and set the bi-polar offset potentiometer to give zero reading on all channels.
Refer to the manual for this module for more information.

RA and DEC Quick motion pre-amplifiers

The best instrument to use for these tests is the Datron DVM.

Obtain technical folder: FI/PA/00 on servo control electronics and referring to the circuit diagrams, check the following offsets:

  1. Set the telescope to computer mode, but do not apply a demand.
  2. RA Quick motion pre-amplifier: on test point TP1, adjust VR5 for zero  +/- 0.1mV
  3. RA Quick motion pre-amplifier: on test point TP2, adjust VR6 for zero  +/- 0.1mV
  4. DEC Quick motion pre-amplifier: on test point TP1, adjust VR5 for zero  +/- 0.1mV
  5. DEC Quick motion pre-amplifier: on test point TP2, adjust VR6 for zero  +/- 0.1mV

RA and DEC Slow motion pre-amplifiers

  1. Set the telescope to computer mode, but do not apply a demand.
  2. RA Slow motion pre-amplifier: on test point TP7, adjust VR1 for zero  +/- 0.1mV
  3. RA Slow motion pre-amplifier: on test point TP8, adjust VR4 for zero  +/- 0.1mV
  4. DEC Slow motion pre-amplifier: on test point TP7, adjust VR1 for zero  +/- 0.1mV
  5. DEC Slow motion pre-amplifier: on test point TP8, adjust VR4 for zero  +/- 0.1mV

Diagnostic aids

At the bottom of the engineering control rack there is a small switch box. This can be connected to an oscilloscope and used as a diagnostic aid.

The switch box can be switched to select different signals such as the LEAD and LAG signals from the Baldwin encoders and  the DAC demand to the pre-amplifiers.

CAMAC

The CAMAC system is fully described in the manual:  INT CAMAC. A description of how to use the DEC ALPHA computer CAMTEST program along with examples for each module are given to aid fault finding.

The BCNAF commands in the CAMAC manual are just the useful ones. More information can be found in the specific module handbooks kept in the filing cabinet in the INT electronics workshop.

TIME SERVICE

Full details can be found in the manual:  ING TIME SERVICE

Last edited:  Aug 2002  ejm