H2S Four Channel Monitor – Model 422

Model 422 H2S Monitor has four channels. The system is designed to monitor H2S in the ppm levels.


  • Work-Over Rigs
  • Refineries
  • Drilling Platforms and Rigs
  • Gas and Oil Production Platforms
  • Mud-Logging Operations
  • Desulfurization Facilities
  • Sulfur Recovery Plants
  • Sewage Disposal Operations
  • Chemical Plants
  • Pulp and Paper Mills

Four Channel monitoring

General Purpose Enclosure

High Alarm Per Channel

Low Alarm Per Channel

4-20 mA Output Per Channel

Fast Response Time

Detection Method

Electro-chemical (Estimated life: 3 Years)

Communications Output

4-20 mA (Self Powered)


(See Customization Tab for other options)

Response Time

0-50ppm < 10 Seconds with 50ppm H2S

Instrument Accuracy

± 5% Full Scale

Instrument Repeatability

+/- 2%

Operating Temperature

-20°C to 50°C; -40°F to 122°F

Sensitivity Range

Detection of < 500 ppb up to % Ranges of H2S
No Loss of Sensitivity or Response Time Due to Lack of Exposure to H2S
No Poisoning

Humidity Range

Not affected by humidity

Alarm Circuits

Two Independent SPDT Relays for Low and High Alarm

  • 0.5A @ 125v AC
  • 2.0A @ 30v DC

C/NO/NC dry contacts
Alarms are Field Adjustable
Low Alarm Activates Red Strobe
High Alarm Activates Buzzer
All Relays are set Fail Safe

Interference Data

No Effect: Methane, Ethane, Propane, Butane, Hexane, Carbon Monoxide, Sulfur Dioxide
3 to 1: Methyl Mercaptan
No Effect up to 1%: Hydrogen
No Effect up to 5%: Dimethyl Sulfide
No Effect up to 5%: Dimethyl Disulfide



  • 0-5 PPM
  • 0-10 PPM
  • 0-20 PPM
  • 0-50 PPM
  • 0-100 PPM
  • 0-200 PPM


Communications Output
  • 4-20 Self Powered (Standard)
  • Modbus via RTU (Standard)
  • Modbus via TCP/IP
Power Input
  • 12 VDC
  • 24 VDC
  • 110 VAC
Alarm Relays

Two Independent SPDT Relays for Low and High Alarm

Low Alarm Activates Red Strobe

High Alarm Activates Buzzer

Relays are set for FAIL SAFE

Alarm Setpoints, Latching, and Non Latching are PLC Programmable

Relay Ratings:

  • 2.5A @ 125v AC
  • 4.0A @ 24v DC
Alarm Delay

An Alarm Delay is PLC Programmable

The delay can be set for 0-90 minutes

H2S 422 Catalog SheetViewDownload
H2S Transmitter Catalog SheetViewDownload