User`s guide

Installation and Setup
44
The contacts remain closed for 6 seconds. The Start signal is
normally used to start a GC run, by connecting it to the GC Start
terminals. See Figure 4.
Fail Output Signal —The ATD/TD can be used with
instrumentation that is unable to read the BCD sample tube number
and therefore unable to report it with the chromatographic results.
(Also useful even if BCD is present, to synchronize data handling
sequence with ATD/TD sequence.) In this situation, care is required
when a chromatogram is assigned to a particular sample tube. This is
due to the fact that synchronization between the ATD/TD and such
instrumentation is usually provided by the Inject signal from the
ATD/TD, which starts the GC.
If processing of a tube is started by the ATD/TD, but is stopped, for
example, by a fault condition, a GC run is not performed for this vial
because an Inject signal is not generated. The next GC run is
produced only when the sample from the following tube has been
injected onto the GC. There will be gaps in the GC runs
corresponding to samples that were not successfully transferred to
the GC.
Although the position of these gaps can be determined from the Log
tab, some data handling systems automatically increment the sample
number that is reported with the chromatographic data. This can be
misleading.
The fail output signal consists of a relay contact closure between
pins 7 and 8 (Fail Out). See Figure 1. This is used to indicate that
although an analysis has been started by the ATD/TD, no Start signal
will be produced. This signals to an external device that the expected
sample will not be transferred and that there will be a gap in the
chromatographic data. Under these circumstances, the Fail signal
can be connected to the external device in parallel with the Inject
signal so that either signal can start the run. This results in blank runs
being generated for tubes that fail, but synchronization of the ATD/
TD and the other instrumentation is maintained. See Figure 2.
NOTE: Depending on the configuration of the external
instrumentation, it may be more appropriate to connect the
Fail signal elsewhere, e.g., to a data handling system.
Many variations are possible.