Electrochemical 2-Wire Toxic Gas Detector 4501-XX

Electrochemical 2-Wire Toxic Gas Detectors 4501-XX

Sierra Monitor’s 4501-XX Detector monitors toxic gases such as Hydrogen Sulfide (H2S), Carbon Monoxide (CO), Oxygen (O2) Deficiency, Chlorine Dioxide (ClO2), and others.

The 4501-XX detector is based on electrochemical technology, a proven, less-expensive option that offers high accuracy, low power requirements, and sensitivity to a particular gas in the parts-per-million range.

Hydrogen Sulfide detection Equipment

Utilizing 2-wire loop-powered technology, the 4501-XX detector requires less wiring when being installed, leading to better protection against wiring errors. This also allows for a direct interface to common PLC and DCS. With its compact size, the 4501-XX requires minimal maintenance with a 180-day calibration cycle and continuous self-diagnostics.

The Electrochemical 2-Wire Toxic Gas Detector 4501-XX is approved and certified by a variety of third-party agencies, including FM, CSA, ATEX, and IECEx. These approvals and certifications assure our customers that we carry only the highest quality of products and performance.

2-Wire Loop-Powered Technology

Directly interface to common PLC and DCS and powered for easy installation and reduced installation costs

LCD Display

Easily access gas status, calibration instructions, adjustment of ranges and outputs, and diagnostic information with a user-friendly operator interface

Non-Intrusive Calibration

Calibrate the sensor without declassifying the area

4-20 mA Output

Interface effortlessly with common factory communication links and provide flexibility for the output

FM-Approved 6 Month Calibration Interval

Dramatically reduce maintenance for the user

Application Adaptability

Select various ranges and mount the detector in various orientations with a rotatable face plate

Internal Continuous Self-Diagnostics

Automatically indicate any fault or optics problems

Model Number Max. Gas Range (1) Resolution Response Time (2) Sensor Life
4501-03 O2 0-25% Vol. 0.2% Vol. <10 Seconds 20 Months
4501-04 CO 0-1,200 PPM 0.5 PPM <25 Seconds 2 Years
4501-05 H2S 0-100 PPM 0.1 PPM <30 Seconds 2 Years
4501-06 Cl2 0-10 PPM 0.1 PPM <60 Seconds 2 Years
acetic acid 4100-34 4100-35 4100-35 4100-35
4501-08 ClO2 0-3 PPM 0.1 PPM <60 Seconds 2 Years
4501-10 SO2 0-100 PPM 0.5 PPM <20 Seconds 2 Years
4501-12 NO2 0-20 PPM 0.2 PPM <35 Seconds 2 Years
4501-25 NH3 0-100 PPM 1.0 PPM <30 Seconds (3)
4501-26 HF 0-10 PPM 1.0 PPM <90 Seconds (3)
1. Other ranges available 2. To 90% range 3. NH3 and HF sensor requires electrolyte recharge up to year

lectrochemical, 2-Wire


Display: LCD, 2-line, 16-characters

Signal Output: 2-wire sensor powered analog 4-20 mA (Trouble 3.6 mA)

Loop Resistance: 800 ohm

Electrical Data

Power consumption: 0.2 watts

Connection type: 2-wire, loop-powered

Input voltage: 24 VDC nominal: 14-30 VDC

RFI/EMI Protection: EN50081-2, EN50082-2

Operating Range

Ambient Temperature Range:

  • Standard: -4o to 122oF (-20o to 50oC)
  • 4501-25/26: 14o to 113oF (-10o to 45oC)
  • Extended Temperature: Sensor and 4-20 mA will continue to operate at -40oF (-40oC) but the LCD display will decay over time if exposed to temperatures below -4o (-20oC) for significant time (not for 4501-25)

Storage Temperature: -4o to 122oF (-20o to 50oC)

Relative Humidity:

  • Standard: 15-90%
  • 4501-25/26: 20-90%

Dimensions (H x W x D):

  • Standard: 7.0 x 3.6 x 4.0 in. (17.8 x 9.1 x 11.2 cm)
  • 4501-25/26: 8.4 x 4.4 x 3.9 in. (21.3 x 11.2 x 9.9 cm)


  • Standard: 2.2 lb. (1.0 Kg) Aluminum or 4.6 lb. (2.1 Kg) SS
  • 4501-25/26: 3.0 lb. (1.3 Kg) Aluminum or 5.0 lb. (2.3 Kg) SS

Enclosure: Aluminum, Stainless Steel


Hazardous location: Explosion proof, NEMA 4X


  • Class I, Div. 1, Groups B, C, D
  • Class II Div. 1, Groups E, F, G


  • Class I, Div. 1, Groups B, C, D
  • Class II Div. 1, Groups E, F, G

4501-05 FM Performance Approval:

  • 4501-05 Approval FM ISA-92.0.01, Part I-1998 and FM 3600

ATEX (4501-05): II 2G, Ex d IIB + H2 T6 TA = 22 oC to 5oC

IECEx (4501-05): Certificate of Approval

CQSTL (4501-05): Certificate for China

Limited warranty: 2 years

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