Spectrex Quasar 900 Open-Path Gas Detection System - Manual (Page 32)

SafEye TM Quasar 900 Gas Detector
20 Electrical Specifications
Immunity to false
alarm: Does not produce false alarm and is not
influenced by Solar Radiation, Hydrocarbon
Flames and other external IR Radiation Sources.
4.2 Electrical Specifications
Operating Voltage: 18-32 VDC
4.2.1 Power Consumption
Table 9: Detector and Source Maximum Power Consumption
Without Heated
Optic (Max.) With Heated
Optic (Max.)
Detector 200mA 250mA
Source 200mA 250mA
4.2.2 Electrical input protection
The input circuit is protected against voltage-reversed polarity, voltage
transients, surges and spikes according to EN50270.
4.2.3 Electrical outputs
4.2.3.1 0-20mA Current Output
The 0-20mA is isolated sink option. This output can be configured as Source
(see Appendix A).
The maximum permitted load resistance is 600 ohm.
4.2.3.2 Communication Network
The Detector is equipped with an RS 485-communication link that can be
used in installations with computerized controllers.
Communication is compatible with the Modbus protocol:
 This protocol is a standard and is widely used.
 It enables continuous communication between a single standard Modbus
controller (Master device) and a serial Network of up to 247 Detectors.
 It enables connection between different types of Spectrex Detectors or
other Modbus devices to the same Network.
4.2.3.3 HART Protocol
The HART Protocol is a digital communication signal at low level on top of
the 0-20mA.
This is a bi-directional field communications protocol used to communicate
between intelligent field instruments and the Host System.