INFICON Maxtek PM-700 Plating Monitor - Manual (Page 53)

PM-700 SERIES PLATING MONITOR
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4.8.3 Digital to Analog Converters
Two independent Digital to Analog Converters (DAC's) are provided, one for
Rate and one for Thickness. The DAC outputs have a range of 0 to 5 volts dc.
Refer to Figure 11 for the DAC connector outline and Table 5 below for the pin
out assignments.
4.8.3.1 Thickness DAC
The scale factor of the thickness DAC is established by the Programmable
Parameter DAC Thickness Range, which establishes the full scale value of the
DAC. i.e. setting the DAC Thickness Range at 500 microns will result in a DAC
output which varies linearly from 0 to 5 volts as the thickness varies from 0 to 500
microns. The measurement units for the DAC are the same as those for the
Thickness display. The quantity that is converted is the magnitude of the
Thickness; therefore, an increasingly negative Thickness going from 0 to -500
microns will also be converted to a 0 to 5 volt dc output.
4.8.3.2 Rate DAC
The scale factor of the Rate DAC is established by the two parameters, Low DAC
Rate and High DAC Rate. The output of the DAC varies linearly from 0 to 5
volts dc as the magnitude of the Rate varies from the Low DAC Rate level to the
High DAC Rate level. Negative rates are converted to the same output as positive
rates of the same magnitude. Assuming that the nominal rate of the process is 1.5
microns per minute we might set the Low DAC Rate at 1 micron per minute and
the High DAC Rate at 2 microns per minute. In this case the output will vary
linearly from 0 to 5 volts dc as the Rate varies from 1.0 micron per minute to 2.0
microns per minute. A rate of 1.5 microns per minute would result in an output of
2.5 volts dc. For rates between 0 and the Low DAC Rate value, the DAC output
is held at zero. At Rate magnitudes above the High DAC Rate value, the DAC
output is held at 5 volts.