Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

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Electronics
14
Troubleshooting and Maintenance Guide 227
Interfacing to External Devices
Remote control processor
The remote control processor on the LAN/MS control card
synchronizes start-run signals with external devices. The
functions of the remote control processor are extended to the
remote start (Remote) connector (
Figure 37 ) on the side panel
of the instrument. The remote start cable connects the external
devices and the GC/MSD.
Remote start signals
It is often necessary to communicate with external devices (for
example, a purge-and-trap) during a run. Typically, these
communications are requests to send a system-ready signal.
They also include:
• Receive a start run signal from an external device
• Program the timing of events during a run
System ready
When interfacing to an external device, it is often desirable to
send a system-ready signal to the device. In the case of a
multisample Tekmar purge-and-trap, each sample is purged
onto a trap where it waits for a ready signal. On receipt of the
ready signal, the desorbtion cycle begins. When a specific
temperature is reached, the purge-and-trap closes a contact to
indicate the run has started.
The ready pin on the remote start connector on the instrument
is held low at all times except when the GC, MSD, and data
system are all ready. On system ready, a logic high of 5 VDC is
Figure 37 Remote start connector
Start Ground
Ready