An on-board microcomputer coordinates the movement of the six (Mark II and Mark EI) or seven (Mark IV and Mark V) stepping motors located in the instrument as well as the azimuth drive located in the mounting box beneath the instrument. This microcomputer provides the time base for coordinating the movement of the slit mask and the accumulation of photon counts in appropriate memory registers. It also controls the switching of the lamps, and monitors various supply voltages and temperature readings at different locations inside the instrument. Wired communication with a separate control computer, which is usually located indoors, is done through an RS-232 communication port. The microcomputer accepts ASCII commands, executes each command task, and signals the task completion back to the control computer. Multiple commands can be sequenced and executed in order of sequence.
Instruments operating in cold climates are heated to limit the lower range of operation. Should the temperature drop below a specified value (between 5°C and 20°C), a thermostat switches on the heaters inside the instrument box. Some Brewer instruments have been modified to operate in a thermally regulated (both heated and cooled) environment that allows minimal temperature variability.
Other electronics inside the instrument include power supplies for several components of the instrument. These components include the mercury and standard lamps, the high voltage for the photomultiplier, drive supplies for the stepping motors, and the heaters.
Was this article helpful?