INFICON MDC-360 Thin Film Deposition Controller - Manual (Page 30)

MDC-360 DEPOSITION CONTROLLER
3-6 BENCH CHECKOUT & INSPECTION
In addition to the individual channel output pins there are two control pins which
are common to both channels and are intended to simplify the process of setting
up analog recorders. Connecting the Zero control line to ground will drive both
channel outputs to zero, allowing the recorder zero reference to be easily set.
Releasing the Zero line and connecting the Full Scale line to ground will drive
both channel outputs to full scale for establishing the recorder full scale
calibration.
Each channel can be set independently to convert either the two or the three least
significant digits of the chosen parameter to a proportional analog signal,
corresponding to the DAC setup option chosen. With the three digit setting, a
thickness of 0.500 KÅ would result in an analog output of 2.50 volts, or a scale
factor of 5 mV/Å. If more resolution is desired, either channel can be configured
to convert only the last two digits of the parameter, thus the analog output would
achieve full scale at 99Å. The output scale factor in this configuration is 50
mV/Å.
The above scale factors are based on the assumption that the thickness display is
in the 0 - 9.999 KÅ range. Because the thickness and rate displays are auto-
ranging, the analog output of these variables will also autorange so that in the
above example, if the thickness is in the range of 10 KÅ to 99.9 KÅ, the analog
scale factor would be 50 millivolts per 10 Å, also ten times larger.
The Rate deviation parameter must be handled differently than the other
parameters because it can be negative. Maximum positive error is converted to 5
volts, maximum negative error is converted to 0 volts and zero error is converted
to a mid scale, 2.5 volt, output. Maximum corresponds to 99 or 999, plus 1.
The DAC can be checked by putting the MDC-360 into the Simulate mode and
checking for correspondence between the analog output and the selected front
panel displays.