AirTest CN9000 Series Руководство - Страница 2
Просмотреть онлайн или скачать pdf Руководство для Контроллер AirTest CN9000 Series. AirTest CN9000 Series 10 страниц. Sensor controller
AirTest Model CN9000 Series Sensor Controller
THEORY OF OPERATION continued
A TYPICAL SYSTEM WALK THROUGH
The external sensor's power and 4-20mA status signal wires are connected to the input modules wiring
terminals. Processing of the 4-20mA takes the form of a comparator circuit where it's digi t al output si g nal
changes state when the voltage across the 100 ohm current sensing resistor is greater than a reference voltage.
The voltage at which the state change occurs is called the "tri p point".
The trip point voltage can be a fixed value, as in the sensor fail detect (out of operating range) circuit or be
variable through user adjustable trim potentiometers. The base input module incorporates four comparator
outputs, 2 of which have user settable trip points and the remaining 2 are have fixed trip points for high and
low sensor fault conditions. The 2 fault state comparator outputs are tied common to allow one fault
condition signal. The resulting 3 digital signals are placed onto 1 of 16 available signal channels on the
interconnect board through jumpers on the input module.
The signals avail a ble on the interconnect board are used by the output module. Channel selection is
accomplished but setting the appropri a te jumper on the output module. There are 3 channel selection blocks, 1
for each of the 5 amp relays.
Common controller configurations use 3 relays as the final output to external devices. A ventilation system is
acti v ated by the contact closure of a relay when a low gas level is detected, while a second relay activates an
audi b le and/or vi s ual alarm when the gas level reaches a higher level i n dicating a possible problem with the
ventilation system. The third relay is used to signal a fault with the system such a sensor signal loss which may
indi c ate a sensor fault or a break it sensor wiring. In any case it is important to incorporate basic fault detection
into any safety system.
Distributed By:
GLOBAL CONTROLS, INC.
3008-B 16TH AVE W.
SEATTLE, WA 98119
(800) 821-4863 TOLL FREE
(206) 282-4666 TEL
(206) 282-4888 FAX
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