Scion Instruments 436-GC Service Manual page 76

436-GC/456-GC
EIC PWA Digital Interface.
The three module Select bits are connected to J2 pins 2,4 & 6. For selection of Module #1, a jumper
connects J2 pin 2 to J2 pin 1 on the EFC PWA. When EFC1SEL goes low it selects U1 and permits the
address bits EFCA1 through EFCA3 to be decoded.
Modules #2 and #3 are selected in a similar manner by moving the jumper to positions that connect pins 4
to 3 and 6 to 5 respectively.
U2 is a serial EEPROM which is addressed by all address bits high. Serial communication to U2 is via a
serial interface comprised of S2CLK, 521N and S2OUT.
U3 is a serial shift register with latched outputs, that is used for configuring the EIC. With SYSENAB low the
input shift register of U3 is reset to zero, but the output remains unaffected.
After SYSENAB is released and goes high U3 can be addressed and loaded via the serial interface. In
order to strobe the data to the output of U3, U1 should be addressed with (000). Outputs of U3 are
assigned as follows:
Bit#
QA
QB
QC
QD
QE
QF
QG
QH
U4 is a dual 12 bit serial input DAC. It is loaded by writing 24 bits over the serial bus while
address (011) is active, and then writing address (010) to load the data.
EIC PWA Analog Interface.
A single analog signal is returned to the main board over the EFC ribbon cable.
This signal is IEFCANLG, and is multiplexed on the EFC PWA. U5 is a quad analog
switch that is connected up as a 4 channel multiplexer. Analog signals called Temp,Valve
Diag,Pressure & Flow are selected by turning on the appropriate bits from the serial shift
register U3. R22,C6,R21,C5,AR3 and R60 form a filter and output buffer circuit for the
Flow signal. R60 is a pull up used to improve the capacitive load tolerance of AR3.
Similarly R40,R41,C23,C24 and R61 form a filter and output buffer for the Pressure
signal.
Diagnostics.
R44 and R45 form a divider for the temperature controller diagnostic output. When the
temperature controller is controlling at it's setpoint the output of AR1,7 is at zero volts +/-
the opamp offset. The voltage presented at U5,11 is nominally 2.500 volts. A deviation of
about 80 millivolts is equivalent to one degree Celsius at the output of AR1,7. This
translates to a 40 millivolt change at U5,11.
Power Control.
Q5 & Q6 are used as valve drivers to support up to two switching valves connected to
J2,7/8 and J2,9/10. CR3 and CR4 are snubber diodes.
VR1 is a voltage regulator supplying 14 Volt power to the two proportional valve drivers
formed by Q2 and Q3.When Q7 is turned on the reference input to VR1 is shorted to
ground, effectively turning off the +14 Volt supply. Heater power can be turned off by
turning on Q1, which removes base drive to Q4.
SCION Instruments
High
Connect Temp. to EFCANLG
Connect Valve Diag. to IEFCANLG
Connect Flow to IEFCANLG
Connect Pressure to IEFCANLG
Turn on Split/Splitless Valve
Turn on Septum Valve
Turn on 14 Volt supply
Tur Turn off Block Heater
436-GC/456-GC Service Manual Revision B February 2019
Low
Disconnect Temp.
Disconnect Valve Diag.
Disconnect Flow.
Disconnect Pressure.
Turn off Valve.
Turn off Valve.
Turn off Supply.
Turn on Heater.
610 Hardware description
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