Oldham Simtronics GD1-L0T-31KH-0XJ-A3 GD1 Transmitter H2S 200 ppm*m, 75m range. ATEX, IECEx, 4-20mA, sink

What is the Oldham Simtronics GD1-L0T-31KH-0XJ-A3?

The Oldham Simtronics GD1-L0T-31KH-0XJ-A3 is: GD1 Transmitter H2S 200 ppm*m, 75m range. ATEX, IECEx, 4-20mA, sink, HART. The GD1 is a laser based open path detector for hydrogen sulphide, built as a separate transmitter and receiver. The transmitter emits an infrared laser beam, shaped as a cone rather than a focused pointer beam, and the receiver measures how much light the gas absorbs along the line of sight. The laser diode wavelength is monitored more than 500 times per second so that the absorption line keeps matching the target gas, which is why the detector needs no on-site calibration for its whole life and shows no cross interference from other gases. The laser is Class 1 and eye safe, and both transmitter and receiver have heated optics inside stainless steel housings. The GD1 Open Path Laser Gas Detectors group in the 2026 price book lists 24 orderable part numbers, and ordered against ATEX approval, with the 4-20 mA current sink output stage, covering 200 ppm*m.

What are the specifications of the GD1 Open Path Laser Gas Detectors?

• Detection method: near infrared laser scanning with a tunable laser diode, Class 1 eye safe
• Detected gas: hydrogen sulphide (H2S)
• Range: 0 to 200 ppm*m default; path length 5 to 75 m
• Accuracy and repeatability: better than plus or minus 8 ppm*m (under plus or minus 4% of full range)
• Response time: 5 seconds
• Output: 4-20 mA sink or source, factory set, maximum load impedance 500 ohm, with HART
• Fault signalling: 1 mA fault, 2 mA beam block, optional 3 mA warning; beam block declared above 98% obscuration
• Alignment tolerance plus or minus 0.3 degrees, with heated optics on both transmitter and receiver
• Safety Integrity Level 2, with a functional test interval of once per year
• Calibration factory set, no field recalibration

What should you check before ordering?

The GD1 carries a 5 year limited warranty, and it is void if the detector was installed or operated outside the procedures in the operating manual. Alignment is the field risk worth planning for: the laser beam presents a smaller target area than a conventional open path system, so it needs higher alignment accuracy to reach sufficient optical transmission, and poor alignment reduces system performance rather than failing outright. During alignment the 4-20 mA output holds at 2 mA and at power up it holds 1 mA, so a control room seeing those values during commissioning is reading a documented state, not a fault.

How do the part numbers differ?

The price book lists three orderable forms of the same optical path: a complete System (transmitter and receiver together), a Transmitter on its own, and a Receiver on its own, so a damaged half can be replaced without rebuying the pair.

Where is it used?

Typical service: Perimeter and fence line hydrogen sulphide monitoring; Open outdoor structures where a single path replaces multiple point detectors; Property boundary monitoring on oil and gas sites; Installations where cross interference from other gases must be excluded.

How do I order or get a quote?

PE Energy supplies the Oldham Simtronics GD1-L0T-31KH-0XJ-A3 on a quote basis: send the part number with your application details and we return pricing and lead time. Fixed gas and flame detection is quoted rather than listed because most references ship configured for target gas, range, approval scope and cable entry, and those choices are fixed at the part number. This part belongs to the same product line as the GD1 laser open path H2S gas detector already in our catalogue.