SENS.413347.015RE
10
- "Relay 2" (14), for connection of circuits switched by signal relay 2.
Screw terminal clamp "4...20 mA" contains circuits:
- "lin", for load connection (current flowing in);
- "lout", for load connection ((current flowing out).
Screw terminal clamp "SENS" contains circuits:
- "+", for connection of positive power supply conductor;
- "L", for connection of signal conductor of SENS line;
- "-", for connection of common (negative) power supply conductor.
Screw terminal clamp "RS-485" contains circuits:
- "B", for connection of B (D-) signal conductor of RS-485 cable;
- "A", for connection of A (D+) signal conductor of RS-485 cable;
- "Com" for connection of "Common' conductor of RS-485 cable.
Electronic unit contains "SENSOR" (15) connector for connection of PT cable.
Primary transducer (16) is located in compartment for PT installation. The compartment
is covered with protective cap (20). And is fixed by stopper screw 22 from self-unscrewing.
7.2 Operation principle
7.2.1 Principle of Gas Detector operation is based on the absorption of radiation in the
infrared specter part by the detectable gases and subsequent transformation of the measured
concentration of gas or vapor into a digital output signal. With passage of infrared radiation
through the analyzed medium, radiation is partly absorbed, which leads to change of optic
sensor signal in proportion to amount of gas or vapors.
7.2.2 Gas detector operates in automatic mode when power is supplied, in accordance
with specified configuration parameters.
Gas detector performs measurement of concentration and forms output analog unified
current signal 4...20 mA which is proportional to the measured concentration (only gas
detector models with interface 4...20 mA). Upon request from devices performing display and
processing of information, gas detector transmits digital signal HART to "current loop" line,
which corresponds to measured value of concentration (only gas detector models with HART
interface).
Upon request from devices performing display and processing of information, gas
detector transmits digital signal to RS-485 line, which corresponds to measured value of
concentration (only gas detector models with RS-485 interface).
Upon request from devices performing display and processing of information, gas
detector transmits digital signal to SENS line, which corresponds to measured value of
concentration (only gas detector models with SENS interface).
Gas detector implements output of information about measured value of concentration
using built-in digital indicator (only gas detector models with built-in digital indicator).
When specified threshold value of gases or vapors concentration is exceeded, a
corresponding bit is set in the status byte of gas detector in accordance with Annex H. Status
byte is transmitted by gas detector to the SENS line, received and analyzed by other devices:
switching units, power and switching units (BK and BPK type), light, sound signaling devices
(VS type), multichannel signaling devices (MS-K, VS-K type), which use the fact of change or
existence of specified bit, in accordance with their settings, to switch circuits of actuating
devices, turning on or off light and/or sound signaling.
Gas detector provides switching of contacts of two signal relays in case of specified
concentration exceeding, initiation of failure or other events (only gas detector models with
relay).
7.2.3 Gas detector at the installation location, using indicators on face panel, provides
light indication and signaling:
