Posted in | Gas Sensors

Detection of Carbon Monoxide and Hydrogen Sulfide with the SGX-4DT / SGX-4CO / SGX-4H2S

SGX Sensortech has developed a range of electrochemical sensors for detecting carbon monoxide and hydrogen sulphide.

These sensors are replacements for present-day electrochemical sensors and the electrical properties of the SGX Sensortech sensors will be identical for all applications.

This is because of the electrochemistry of the catalysts used and the mechanical design of the sensor.

 

SGX-4DT - Industrial Dual Toxic Sensor (CO and H2S)

Application : Portable Multi-Gas Safety Instrument

Performance Characteristics

The performance characteristics of the SGX-4DT are:

  • Range - 0 - 500ppmCO,0-200ppm H2S
  • Output Signal -80 ± 30 nA / ppm CO
    • 775 ± 275 nA/ ppm H2S
  • Linearity - Linear
  • Repeatability - < ± 3% CO equivalent
    • < ± 2% H2S equivalent
  • Response time, t90 - <30 s
  • Maximum Overload - 2000ppm CO
    • 500 ppm H2S
  • Long-term output drift - <5% per annum
  • Recommended Load Resistor - 20ohms
  • Warranty - 2years

 

Operating Conditions

The operating conditions of the SGX-4DT are:

  • Temperature range is -30 to +50°C
  • Operating humidity is 15 – 90% RH (non-condensing)
  • Pressure range is 800 mbar to 1200 mbar
  • Recommended storage temperature is 0 °C to 20°C
  • Storage life is 6 months in original packing (0 to 25°C)

 

Intrinsic Safety Data

The intrinsic safety data of the SGX-4DT are:

  • Maximum at 2000ppm - 0.3mA
  • Maximum o/c Voltage - 1.3V
  • Maximum s/c Current <1.0A

 

Product Dimensions

In the Figures 1,2 and 3 the product is shown with dimensions. Please note all dimensions are in mm and all tolerances ±0.15 mm.

Figure 1.

Figure 2.

Figure 3.

Cross-Sensitivity Data

The cross-sensitivity data is shown in Table 1. Kindly note that this is only for reference purposes and calibration must be done with the actual gas at a known concentration. This device is designed to be RoHS compliant.

Table 1. Cross-sensitivity data for the SGX-4DT

GAS CONC. CO H2S
Hydrogen Sulfide 25 ppm < 5 ppm 25 ppm
Sulfur Dioxide 5 ppm 0 ppm < 1 ppm
Hydrogen 100 ppm < 30 ppm < 0.0 5 ppm
Nitric Oxide 35 ppm < 0.1 ppm < 1 ppm
Carbon Monoxide 300 ppm 300 ppm < 5 ppm
Nitrogen Dioxide 5 ppm < 0.1 ppm 0 ppm
Chlorine 15 ppm 0 ppm 0 ppm

Important Notes

  • Using the recommended circuitry from SGX, all performance is based on conditions at 20°C, 50%RH and 1atm
  • Sensor performance is based on temperature.
  • The sensor must not be soldered to the connector pins as this may damage the sensor and thereby invalidate the warranty.

Output temperature coefficient data

Figure 4. Output temperature coefficient data

Poisoning

SGX sensors are developed to function in various harsh environments and conditions. It is however essential that exposure to high concentrations of solvent vapours is prevented at the time of storage, operation and fitting into instruments. While utilizing sensors on PCBs, it is important to use degreasing agents before the sensor is fitted.

Recommended Circuit

  • It is important that the amplifier is of instrumentation quality
  • Capable of low noise and capacitive drive
  • Input Offset < 500µV
  • Recommended load resistor is 20 ohm

The ideal practice is to use a low gain in this circuit and utilise a PGA in the microcontroller.

Op amp suggestions: TLC2252, TLC2254

Recommended circuit for SGX-4DT

Figure 5. Recommended circuit for SGX-4DT

SGX-4CO - Industrial Carbon Monoxide Sensor

Application : Portable Gas Detectors

Performance Characteristics

The performance characteristics of the SGX-4CO are given below:

  • Range is 0 – 1000ppm
  • Output Signal is 70 ± 25nA/ppm
  • Zero Shift (-40°C to +50°C) is<±12 ppm equivalent
  • Linearity is within ±5%
  • Response time, t90is less than30s
  • Maximum Overload is 2000ppm
  • Long-term output drift <20% per annum
  • Recommended Load Resistor 10 ohms
  • Warranty is 2 years

Operating Conditions

The operating conditions of the SGX-4CO are:

  • Temperature range is -30 to +50°C
  • Operating humidity is 15 – 90% RH (non-condensing)
  • Pressure range is atmospheric ±10%
  • Recommended storage temperature is 0°C to 20°C
  • Storage life is 6months in original packing (0 – 25 °C)

Intrinsic Safety Data

The intrinsic safety data of the SGX-4CO are:

  • Maximum at 2000ppm is 0.3mA
  • Maximum o/c voltage is 1.3V
  • Maximum s/c current is <1.0 A

Cross-Sensitivity Data

The cross-sensitivity data are provided in Table 2. Kindly note that this table is just for reference. It is important to perform calibration with the actual gas at a known concentration. This device is designed to be RoHS compliant.

Table 2. Cross-sensitivity data for the SGX-4CO

Gas CONC. SGX-4 H2S
Carbon Monoxide 100 ppm <2 ppm
Sulfur Dioxide 20 ppm 0 pp m
Nitrogen Dioxide 5 ppm <0.5 ppm
Nitric Oxide 50 ppm <0.5 ppm
Ammonia 50 ppm 0 pp m
Chlorine 15 ppm 0 pp m
Ethylene 100 ppm 0 pp m
Carbon Dioxide 5000 ppm 0 pp m

Product Dimensions

In Figure 6, the SGX-4CO is shown with dimensions. All dimensions are in mm and all tolerances are ±0.15 mm

Dimensions of the SGX-4CO

Figure 6. Dimensions of the SGX-4CO

Important Notes

  • Conditions for performance are 20°C, 50% RH and 1 atm, using SGX recommended circuitry
  • Sensor performance is temperature dependant
  • The connector pins must not be soldered as this may damage the sensor and thereby invalidate the warranty. Figure 7 shows the output temperature coefficient data

Output temperature coefficient data

Figure 7. Output temperature coefficient data

Poisoning

SGX sensors are developed for functioning in a broad range of harsh conditions and environments. It is important that high concentration of solvent vapours are avoided, both during storage, fitting into instruments and operation. While using sensors on printed circuit boards (PCBs), degreasing agents should be used prior to the sensor being fitted.

SGX-4H2S - Industrial Hydrogen Sulfide Sensor

Application : Portable Gas Detectors

Performance Characteristics

The performance characteristics of the SGX-4H2S are:

  • Range - 0 – 100 ppm
  • Output Signal - 700 ± 250nA/ppm
  • Zero Shift (-40°C to +50°C) - < ±1 ppm equivalent
  • Linearity - within 5%
  • Response time, t90 - <30 s
  • Maximum overload - 500ppm
  • Long-term output drift - <20% per annum
  • Recommended Load Resistor - 10ohms
  • Warranty - 2 years

Operating Conditions

The operating conditions of the SGX-4H2S are:

  • Temperature range is -20 to +40°C
  • Operating humidity is 15 – 90% RH (non-condensing)
  • Pressure range is Atmospheric ±10%
  • Recommended storage temperature is 0°C to 20°C
  • Storage life is 6 months in original packing (0 – 25°C)

Intrinsic Safety Data

Intrinsic safety data include the following:

  • Maximum at 2000 ppm …………….………..….0.6 mA
  • Maximum o/c Voltage …………………….…...…0.8 V
  • Maximum s/c Current …………………………... <1.0 A

Cross-Sensitivity Data

Table 3. shows the cross-sensitivity data. This table is for reference only. Calibration should be carried out with the actual gas at a known concentration. This device is designed to be RoHS compliant.

Table 3. Cross-sensitivity data for the SGX-4H2S

Gas CONC. SGX-4 H2S
Carbon Monoxide 100 ppm <2 ppm
Sulfur Dioxide 20 ppm 0 pp m
Nitrogen Dioxide 5 ppm <0.5 ppm
Nitric Oxide 50 ppm <0.5 ppm
Ammonia 50 ppm 0 pp m
Chlorine 15 ppm 0 pp m
Ethylene 100 ppm 0 pp m
Carbon Dioxide 5000 ppm 0 pp m

Important Notes

  • All performance is based on conditions at 20°C, 50% RH and 1 atm, using SGX recommended circuitry. Sensor performance is dependant on temperature.
  • Do not solder to the connector pins as this may damage the sensor and thereby invalidate the warranty.

Product Dimensions

All dimensions are in mm and all tolerances are ±0.15 mm.

Poisoning

SGX sensors are developed to operate in an extensive range of harsh environments and conditions. It is however important that exposure to high concentrations of solvent vapours is avoided, both during storage, fitting into instruments and operation. While using sensors on printed circuit boards (PCB’s), degreasing agents should be used prior to the sensor being fitted.

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