Apg Remote Polarity; Apg Remote Signal Electrical Specifications - Agilent Technologies 7697A Advanced Operation Manual

APG Remote Polarity

APG Remote signal electrical specifications

Advanced Operation
The APG Remote start/stop cable is used to synchronize two
or more instruments. The cable carries the signals used to
monitor system readiness between the connected
instruments (HS, GC, and MS/MSD if used) and to send the
start command when a device in the system begins a run.
Typically, in a HS system, the start command comes from
the HS sampler. When the HS is ready for the first injection,
it sends a start signal to the other devices connected using
the APG Remote cable.
The HS provides two choices for APG Remote Polarity, Active
high and Active low.
• Most Agilent instruments respond to Active high. To signal
a start, the signal voltage increases.
• If your GC requires a drop in voltage to indicate a start
command, select Active low.
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 1 K ohms to 1.5 K 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 = 0.4 V.
The bus is passively pulled high. Leakage current out of a
port must be less than 0.2 milliamps to keep the voltage
from being pulled lower than 2.2 Volts. Higher leakage
current may cause the state to be interpreted as a low.
Over- voltage protection: APG Remote connections are
clamped by a zener diode to 5.6 Volts. Exceeding this voltage
will damage the circuit (main board).
5
Configuration
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