INFICON MDC-370 Thin Film Deposition Controller - Manual (Page 95)

MDC-370 DEPOSITION CONTROLLER
7. INPUT/OUTPUT CHARACTERISTICS
The following section describes the electrical characteristics of the MDC-370
inputs and outputs. All outputs are updated and inputs are sampled every 100
msec. In order to insure immunity to transients, inputs are not considered to have
changed until the same input state is obtained on two successive input samples.
For this reason all input signals must have a minimum duration of at least 0.2 sec.
Input signals lasting less than 100 msec. will be ignored while signals lasting
between 100 and 200 msec. may or may not be recognized.
7.1 SOURCE CONTROL VOLTAGE OUTPUT
For maximum noise immunity, each two-terminal control voltage output pair is
isolated from controller ground. Either terminal can be grounded within the user
system, so the output can provide either a negative or positive output voltage
range. In the event that the receiving equipment has an isolated input, one of the
two lines should be grounded to avoid excessive voltage buildup on the otherwise
isolated circuitry.
The voltage output range can be programmed (see Source Setup) for 2.5, 5.0 or 10
volts full scale. The output impedance is nominally 100 ohms. The outputs are
short circuit protected with short circuit current limited to between 20 and 40
milliamps, though the outputs should not be short-circuited for long periods. The
schematic appears in Figure 7-5.
CAUTION
Long term shorting of any of the Source outputs may cause excessive
temperature rise in the isolated power supply and should be avoided.
7.2 SENSOR INPUT
The sensor oscillator is connected through a single coaxial cable. Sensor ground
is common with the MDC-370 ground. Power to the sensor oscillator is carried
on the center conductor of the coaxial cable. Power is supplied from the MDC-
370 internal 5 volt supply through a 50 ohm resistor which accomplishes the dual
function of properly terminating the 50 ohm coaxial cable and providing short
circuit protection. The sensor buffer circuit is shown schematically in Figure 7-4.
7.3 DISCRETE OUTPUTS
Each Discrete Output is an isolated, independent, normally open relay output
connected to one pin pair on the output connector. See Table 8-4 for pin signal
assignments.
INPUT/OUTPUT CHARACTERISTICS 7-1