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Gas Sensor Transmitter/Monitor


Bacharach's new state-of-the-art GDX-350 transmitters, with Smart Sensor technology, provide
accurate and continuous detection of toxic, combustible and asphyxiate gases. The full-featured
design of the GDX-350 includes a large LCD display, a 4-20 mA interface, programmable alarms,
optional relays and a Modbus interface. Exclusive pre-calibrated replacement sensor technology
makes occasional maintenance practically effortless. Specially designed to function in the extreme
temperature conditions found in blast chillers and deep freezers, the rugged construction, intrinsic
safety capability (in two-wire mode with barrier) and an explosion-proof housing allow the GDX-350
to be placed in hazardous-rated areas of many industrial environments - delivering reliable,
superior-sensing performance to protect human life, equipment and property.

Features & Benefits

  • Pre-calibrated Smart Sensor capability with 'plug-n-play' convenience minimizes maintenance and downtime
  • Non-Dispersive Infrared (NDIR), Catalytic Bead and Electrochemical sensor options available
  • Can be placed directly in hazardous environments where leaks occur for quick detection and rapid response
  • Graphic LCD for real-time monitoring of concentrations
  • 4-20 mA, optional Modbus RTU® and wireless interface
  • Easily update alarm set points, configurations or maintenance modes using the LCD display
  • 30-minute onboard data trend


Gas Type Measuring Range Display Increments Sensor Type
Ammonia (NH3) 0-500 ppm 1 ppm Electrochemical
Carbon Dioxide (CO2 ) 0-5% vol 0.1% Infrared (NDIR)
Carbon Monoxide (CO) 0-1000 ppm 1 ppm Electrochemical
Hydrogen (H2) 0-1000 ppm 1 ppm Electrochemical
Hydrogen Sulfide (H2S) 0-500 ppm 1 ppm Electrochemical
Hydrocarbon (CH4) 0-100% LEL 1% Infrared (NDIR)
Methane (CH4) 0-100% LEL 1% Catalytic Bead
Nitrogen Dioxide (NO2) 0-99.9 ppm 0.1 ppm Electrochemical
Oxygen (O2) 0-25% 0.1% Electrochemical
Phosphine (PH3) 0-5 ppm 0.01 ppm Electrochemical
Propane (C3H8) 0-100% LEL 1% Infrared (NDIR)
Sulfur Dioxide (SO2) 0-99.9 ppm 0.1 ppm Electrochemical


Dimensions 8.0" x 5.5" x 4.61" (20.32 cm x 13.97 cm x 11.71 cm)
Housing Durable Aluminum Enclosure - Suitable for Class 1, Div. 1 & 2, Groups B, C, D
Front Panel 5 Indicator Lights: Alarm 1, Alarm 2, Fail, In Calibration, and RS-485
User Interface 64 x 128 Pixel LCD Graphic Display for Gas Readings, 30 Minute Trend, Bar Graphing, Engineering Units and Backlight
Operating Temperature Range -40°F to 140°F (-40°C to 60°C)
Ambient Humidity Range 5% - 90% RH Non-Condensing
Security Mode Lock Out Critical Parameters
4-20 mA Output Signal 3-wire, 4-20 mA. Max Loop Resistance is 750 Ω (@24 VDC)
Alarm Relays 3 Configurable Form C (SPDT) Relays rated for 5 amp at 30 VDC or 240 ~ VAC RESISTIVE. | Relay 1 and Relay 2 Level Alarms are
configurable for HIGH or LOW Trip, for Normally Energized (Failsafe) or Normally De-Energized and for Latching or Non-Latching.
Relay 3 is always Normally Energized for Failsafe Operation so any loss of power to the GDX-350 will be indicated as a "FAULT" condition.
Communications RS-485, Modbus®
Power 10 - 30 VDC, 250 mA (@ 24 VDC)
Power Safety Mode Fully automatic system reset. All program parameters are retained.
Approvals CSA: Division 1 & 2, Class 1: Groups B, C, D (excludes NH3

Ordering Information - Common Configurations*

Part Number Description
5600-3011 GDX-350 [CO] 0-1,000 ppm, 3-wire
5600-3021 GDX-350 [H2S] 0-500 ppm, 3-wire
5600-3031 GDX-350 [O2] 0-25%, 3-wire
5600-3041 GDX-350 [NO2] 0-100 ppm, 3-wire
5600-3051 GDX-350 [NH3] 0-500 ppm, 3-wire
5600-3061 GDX-350 [SO2] 0-100 ppm, 3-wire
5600-3071 GDX-350 [PH3] 0-5 ppm, 3-wire
5600-3201 GDX-350 [CH4] 0-100% LEL, Cat. Bead, 3-wire
5600-3211 GDX-350 [CH4] 0-100% LEL, IR, 3-wire
5600-3221 GDX-350 [CO2] 0-5% Vol., IR, 3-wire
5600-3231 GDX-350 [Propane] 0-100% LEL, IR, 3-wire
5600-3241 GDX-350 Pentane 0-100% LEL, IR, 3-wire
5600-3012 GDX-350 [CO] 0-1,000 ppm, 3-wire - with Relays and Modbus®
5600-3022 GDX-350 [H2S] 0-500 ppm, 3-wire - with Relays and Modbus®
5600-3032 GDX-350 [O2] 0-25%, 3-wire - with Relays and Modbus®
5600-3042 GDX-350 [NO2] 0-100 ppm, 3-wire - with Relays and Modbus®
5600-3052 GDX-350 [NH3] 0-500 ppm, 3-wire - with Relays and Modbus®
5600-3202 GDX-350 [CH4] 0-100% LEL, Cat. Bead, 3-wire - with Relays and Modbus®
5600-3212 GDX-350 [CH4] 0-100% LEL, IR, 3-wire - with Relays and Modbus®
5600-3222 GDX-350 [CO2] 0-5% Vol., IR, 3-wire - with Relays and Modbus®
*Customized sensor configurations are available based on your specific needs. Ask your authorized Bacharach representative for details.

Replacement Parts & Accessories

Part NumberDescription
5600-6010GDX-350 Smart CO Sensor, Pre-Calibrated Replacement
5600-6020 GDX-350 Smart H2S Sensor, Pre-Calibrated Replacement
5600-6030 GDX-350 Smart O2 Sensor, Pre-Calibrated Replacement
5600-6040 GDX-350 Smart NO2 Sensor, Pre-Calibrated Replacement
5600-6050 GDX-350 Smart NH3 Sensor, Pre-Calibrated Replacement
5600-6060 GDX-350 Smart SO2 Sensor, Pre-Calibrated Replacement
5600-6070 GDX-350 Smart PH3 Sensor, Pre-Calibrated Replacement
5600-6110 GDX-350 Smart H2 Sensor, Pre-Calibrated Replacement
5600-6200 GDX-350 Smart CH4 Sensor (Cat. Bead), Pre-Calibrated Replacement
5600-6210 GDX-350 Smart CH4 Sensor (IR), Pre-Calibrated Replacement
5600-6220 GDX-350 Smart CO2 Sensor, Pre-Calibrated Replacement
5600-6330 GDX-350 Smart Propane Sensor (IR), Pre-Calibrated Replacement