Models 947, 948 and 960 Leak Detectors Operations and Service Manual
2-9
2.3 Electronic Considerations for the
Optional Rear Panel Interface
This section includes information necessary to interface the 947/948/960 with a PLC or a
host computer using either serial or parallel communications through the optional rear
panel interface via J120 Discrete I/O, J121 BCD Outputs and J123 Host Serial Port.
2.3.1 Discrete I/O J120 Inputs
The discrete I/O is used to control operations via a PLC.
Table 2-2 provides the input
connections.
Table 2-2
J120 Input Connections
Pin on
J120
Input Name
Momentary or Level
Description
1
Ground return for J120 only
2
Reject Output
Active High
Leak rate signal is higher than reject
set point.
3
Stop
200 msec high pulse
Unit goes to vent mode.
4
Start
200 msec high pulse
Goes to fine test via rough gross modes.
6
Parallel Enable
Active High
Enables rear panel PLC Interface.
7
Zero
200 msec high pulse
Begins Auto Zero routine.
9
Auto Cal
200 msec high pulse
Begins Auto Calibrate.
10
Decrement
200 msec high pulse
Decrements the exponent when in manual
ranging.
11
Increment
200 msec high pulse
Increments the exponent when in manual
ranging.
12
Auto Range
Active High
Automatically changes the exponent to
keep the reading in range.
14
Hold
Places the system in Hold mode.
15
Filament Fault
Active High
Active when selected ion source
filament is non-functional.
16
Not Ready
Active High
Not ready to run – possible fault.
18
CAL OK
Active High
Active when last CALIBRATE successful.
19
Zeroing
Active High
Active when Auto Zeroing.
21
Calibrating
Active High
Active when Auto Cal.
