INFICON TM-400 Thin Film Deposition Monitor - Manual (Page 25)

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TM-350/400 Operating Manual
3.3.2 RS-485 Option
1 Remove the chassis top cover.
2 Locate the IC socket labeled U1. It is on the left side along the back of the
TM-350/400’s main board. Remove the device from this socket. This will
disable the standard RS-232 interface.
3 Carefully insert the supplied IC labeled ”U2 RS485” into socket U2, being
careful no to bend any of the pins. It is on the left side along the back of the
TM-350/400’s main board.
4 Carefully insert the supplied IC labeled ”U4 RS485” into socket U4, being
careful no to bend any of the pins. It is on the left side along the back of the
TM-350/400’s main board.
5 Insert the supplied yellow jumper across J22, which is on the left side along the
front of the main board. See
Figure 3-9 on page 3-12 .
6 Replace the chassis top cover.
3.4 Digital To Analog Converter (DAC) Checkout
The built-in DAC function on the Main board contains two converters, allowing
simultaneous recording of Rate and Thickness. The full-scale output of each
converter is 5 volts, is single ended and is referenced to ground.
In addition to the individual channel output pins there are two control pins that 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 displayed Rate and Thickness 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,
using the switches shown in
Figure 3-9 on page 3-12 , to convert only the last two
digits of the parameter, thus the analog output would achieve full scale at 99 Å. 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
autoranging, the analog output of these variables will also autorange. In the above
example, if the thickness were in the range of 10 KÅ to 99.9 KÅ, the analog scale
factor would be 50 mV per 10 Å, also ten times larger.