34 7820A GC Installation Manual
7820A GC Installation Guide
Using the Remote Start/Stop cable
Remote start/stop is used to synchronize two or more
instruments. For example, you might connect an
integrator and the GC so that the [Start]/[Stop] buttons on
either instrument control both of them. You can
synchronize a maximum of ten instruments using Remote
cables.
Connecting Agilent products
If connecting two Agilent products with Remote cables,
the sending and receiving circuits will be compatible—just
plug in both ends of the cable.
Connecting non-Agilent products
If connecting to a non-Agilent product, the following
paragraphs contain information you will need to ensure
compatibility.
APG Remote signal electrical specifications The APG
signals are a modified open collector type. The signal
levels are generally TTL levels (low voltage is logic zero,
high voltage is logic one) but the open circuit voltage will
be between 2.5 and 3.7 Volts. The typical voltage is 3 Volts.
A voltage over 2.2 volts will be interpreted as a high logic
state while a voltage below 0.4 volts will be interpreted as
a low logic state. These levels provide some margin over
the specifications of the devices used.
The pull-up resistance, connected to the open-circuit
voltage, is in the range of about 1K ohms to 1.5K ohms.
For a logic-low state, for a single device on the bus, the
minimum current you must be able to sink is 3.3
milliamps. Since devices are connected in parallel, when
you have multiple devices this minimum current must be
multiplied by the number of devices attached on the bus.
The maximum voltage for a low-input state = 0.4V.
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