VESDA by Xtralis
VESDA VLF-500 Product Guide
www.xtralis.com
13
2.7.2
GPI – General Purpose Input (Terminals 1 & 2)
The General Purpose Input (GPI) is a programmable input. When the GPI function parameter is set to
external, the detector shall indicate an external equipment fault condition by monitoring the line impedance. An
End of Line (EOL) resistor is supplied with the product and must be assembled in parallel with the device to be
monitored.
The EOL resistor provides a known termination to the external equipment, this allows the VESDA VLF to
detect open or short circuits. The detector monitors the EOL resistor (Figure 2-10) and reports any faults when
the GPI function is set to any value, except
None
.
Caution:
These terminal blocks come assembled and should NOT be disassembled.
Avertissement :
Ces borniers sont livrés montés et ne doivent PAS être démontés.
Legend
A
GPI Pin 1
B
GPI Pin 2
Figure 2-9: Terminal and plug set up, GPI connections
The GPI function parameter can be set to the values shown in the table below to achieve several different
functions:
GPI Function
parameter
value
Result
None
GPI is disabled. If GPI will not be used we recommend that you
leave the EOL resistor assembled.
Reset
Detector is reset on activation of the GPI (closing contact).
Note:
The factory-default value of the GPI function is Reset.
Disable
Detector is disabled while GPI is active (contact closed) and reset on
de-activation of the input (contact open).
Standby
Detector is placed in standby (disabled, plus aspirator turned off)
while GPI is active (contact closed) and reset on de-activation of the
input (contact open).
Alarm set 1
Activation of GPI forces alarm threshold set 1 to be used. It overrides
normal selection.
Alarm set 2
Activation of GPI forces alarm threshold set 2 to be used. It overrides
normal selection.
External
Detector indicates a fault while the GPI is active (contact closed).
Typically this is used to monitor external power supply units.
Note:
If the contact is closed it will raise an Instant Fault Finder
No.6 fault. If wire is broken to the monitoring device it will
raise an Instant Fault Finder No.8 fault.
Table 2-1: GPI programming
The GP input detects a short circuit (e.g. the PSU fault relay) at or below 100 Ohms.
