M74050
1/4M IMAGING SPECTROGRAPHS
43
12.2 GRATING TURRET POSITION ERROR
The photo below shows the inside of a MS260i spectrograph. Normally two or three gratings are
mounted on the rotating turret. They are not shown in the photo for clarity. The instrument senses
the turret’s angle of rotation based on a sensor. A small pin mounting just under the turret is seen
by the sensor. The pin position may shift to a location where it cannot be picked up by the sensor
when the instrument is turned on. This may be due to a sudden power outage, inadvertently toggling
the power switch very rapidly or entering an incorrect calibration value (most often a decimal point
error).
To correct this situation, the shaft with the worm gear attached needs to be manually rotated to bring
this pin back to its normal operating range. The normal operating range is shown in green in the
photo below.
Be sure to turn off the spectrograph and unplug it prior to performing this procedure. Take all
necessary precautions outlined in this user’s manual to ensure the optics are not damaged through
inadvertent contact.
Figure 322: Grating Turret Position Sensor Pin Range