Product Overview
The ATi D12 is the explosion-proof, full-feature fixed gas transmitter in the ATi line. A single D12 reads any of 30+ toxic and combustible gases through the interchangeable H-Series smart sensor — up to 46 sensors plug into one transmitter with automatic recognition — and reports on scalable 4–20 mA, with optional alarm relays and HART or Modbus communications. It is built for the hazardous area: a cast-aluminum Class I, Division 1, Groups B/C/D housing that stays sealed during setup — a magnetic tool drives the menus from outside — and an optional Auto-Test that verifies sensor response with a real gas sample on demand. For combustibles and CO₂ that would poison an electrochemical or catalytic cell, the D12Ex-IR variant swaps in a fail-safe NDIR infrared sensor (see Variants).
Other ATi gas transmitters
B12 — loop-powered 2-wire toxic transmitter, lower cost
C12-17 — catalytic-bead combustible %LEL transmitter
D16 PortaSens III — portable hand-held detector for surveys
One platform, two sensing technologies
The D12 reads its gas with an electrochemical or catalytic smart sensor; the D12Ex-IR fits an NDIR infrared cell instead — immune to the poisoning that disables a chemical sensor on combustibles and CO₂. Same explosion-proof transmitter, outputs and communications — pick the sensing technology by the gas and the failure mode you must guard against.
D12
electrochemical / catalytic smart sensor
- 30+ toxic gases and combustible %LEL across 46 interchangeable H-Series sensors
- Optional Auto-Test on-demand gas generator verifies sensor response
- Integral, remote or combustible sensor holders
D12Ex-IR
single-path NDIR infrared
- Methane / %LEL and high hydrocarbons to 100% V/V, plus CO₂ (ppm to 50%)
- Poison-immune and fail-safe — detects its own sensor failure; needs no oxygen
- T90 = 20 s; remote sensor to 100 ft; factory K-factors for 18+ programmed hydrocarbons
Both are the same explosion-proof D12 transmitter (Class I, Div 1, Groups B/C/D) with scalable 4–20 mA, optional three programmable alarm relays, HART or Modbus, the LCD graphics display and the internal data logger — only the sensing technology differs.
Key Features & Benefits
- One transmitter, dozens of gases — the interchangeable H-Series sensor lets a single D12 cover 30+ toxic and combustible gases — one of 46 plug-in sensors for the holder — with automatic sensor recognition so the transmitter knows what is plugged in. Stock one transmitter, not a model per gas.
- Real-gas self-test, not just an electronic check — the optional Auto-Test generates an actual gas sample on demand to verify the sensor responds — a level of confidence an electronic-only self-test cannot match, and it works outdoors in wind. Proof the sensor will see the leak, on a schedule you set.
- Set up and calibrate without opening the box — calibration, alarm setup, reset and configuration are all done through the wall of the explosion-proof enclosure with a magnetic tool, so the housing stays sealed in the hazardous area. No hot-work permit to adjust a transmitter.
- Outputs for whatever reads it — scalable 4–20 mA standard, with optional three programmable alarm relays and HART or Modbus RTU to cover analog, discrete and digital systems from one unit; output simulation tests the whole loop without gas. Wire it to a PLC, a local alarm, or a digital network — or all three.
Specifications
- Detection principle
- Electrochemical or catalytic H-Series smart sensor, matched to the gas; the self-aligning holder accepts up to 46 interchangeable sensors with automatic recognition and verification (the D12Ex-IR variant uses an NDIR infrared sensor — see Variants).
- Target gases
- 30+ toxic and combustible gases — chlorine, ammonia, hydrogen sulfide, ozone, chlorine dioxide, carbon monoxide, hydrogen, oxygen, NO / NO₂, phosgene, ethylene oxide and the semiconductor hydrides (arsine, diborane, germane, phosphine, silane), plus combustible gas as %LEL.
- Measuring range
- Per sensor — from 0–500 ppb (arsine, diborane, germane) and 0–1 ppm (chlorine, bromine, fluorine) through 0–50 ppm (ammonia, CO) to 0–100% LEL combustible and 0–5% O₂; the 4–20 mA output is scalable within each sensor’s range boundaries.
- Sensor (H-Series smart module)
- H-Series interchangeable smart sensor — the cell, amplifier and calibration memory in one plug-in module, with automatic recognition and stored per-sensor calibration history (the field-swap workflow is in the considerations below).
- Accuracy / repeatability
- Generally ±10% of value (limited by the available calibration-gas accuracy), with electronic repeatability ±1% and linearity ±0.5%. Zero drift is under 2% of full scale per month (non-cumulative); span drift is environment-dependent, generally under 3% per month.
- Response time
- Sensor-dependent — set by the electrochemical or catalytic cell fitted. The D12Ex-IR NDIR variant is T₅₀ = 10 s, T₉₀ = 20 s (see Variants).
- Outputs
- Scalable 4–20 mA (loop-powered, 675 Ω max at 24 VDC) standard, plus optional three SPDT alarm relays (5 A @ 230 VAC resistive) — each assignable to any setpoint (Caution / Warning / Alarm) or fault, programmable for setpoint, hysteresis, on-delay, off-delay and manual or automatic reset, with a remote-reset input. Analog- and relay-output simulation allow full loop testing without applying gas.
- Digital communication
- HART (1200-baud Bell 202 FSK) or Modbus RTU (RS-485 / RS-232, up to 247 addresses) — field-ordered.
- Sensor holder / mounting options
- Suffix-F holder choice: integral sensor (with optional Auto-Test gas generator), a remote sensor system for toxic or combustible sensors, or an integral combustible holder — matched to where the gas collects.
- Area classification
- Explosion-proof cast-aluminum housing rated Class I, Division 1, Groups B, C, D — UL, FM and CSA certified.
- Power
- Loop-powered 12–30 VDC, 25 mA in 2-wire mode; 12–30 VDC, 200 mA in 3-wire mode (combustible, relay and backlit builds).
- Display
- LCD graphics display — large gas-concentration numerals, alarm indication and menu-driven setup (backlight available in 3-wire mode). Non-intrusive magnetic-tool operation via four front magnetic switches drives every menu — including data view and alarm reset — through the sealed enclosure, with 4-digit password protection.
- Operating temperature / humidity
- –30 to +60°C for toxic gases (–10°C minimum with an O₂ sensor) and –40 to +70°C for combustibles.
- Calibration
- Optional Auto-Test sensor-response verification — an on-demand electrochemical gas generator confirms response with a real gas sample, even outdoors in wind. Each sensor stores its calibration history; an internal data logger records gas values at user intervals, recallable on the display or over Modbus.
- Dimensions / mounting
- Cast-aluminum explosion-proof enclosure; 4 lb (1.8 kg).
Common Applications
- Semiconductor fabs — toxic hydride monitoring (arsine, diborane, germane, phosphine, silane)
- Water and wastewater disinfection — chlorine, chlorine dioxide and ozone leak and exposure detection
- Chemical processing and refineries — broad toxic and combustible coverage at one point
- Pharmaceutical and food processing — ethylene oxide, ammonia and CO area monitoring
- Metals, aluminium refining and pulp & paper — toxic and combustible safety monitoring
The D12 is the top-of-line fixed transmitter for classified areas. For a lower-cost loop-powered 2-wire toxic point see the B12; for combustible %LEL on a catalytic bead the C12-17; and for a hand-held survey the D16 PortaSens III.
Design & Selection Considerations
- Match the sensor chemistry to the gas — the target gas sets the detection principle: electrochemical for toxic gases (chlorine, ammonia, H₂S, ozone and ~30 others, ppb–ppm), catalytic-bead for combustibles as %LEL (the C12-17), and infrared (NDIR) where a catalytic bead would be poisoned, where oxygen is absent, or for CO₂ and high-level ammonia (the D12Ex-IR and E12-15). Electrochemical for toxics, catalytic for routine combustible-LEL, infrared for poison-prone or oxygen-free service.
- Plan around the H-Series interchangeable smart sensor — the sensor, its amplifier, and a calibration memory live in one plug-in H-Series module, so a freshly calibrated sensor swaps into a live transmitter in the field with no recalibration and no downtime — keep a calibrated spare on the shelf and rotate it on a schedule, and re-task a transmitter to a different gas by fitting a different sensor. The H-Series swap is the single biggest reason the maintenance burden on an ATi system stays low.
- Specify the area classification up front — a classified area drives the protection method and the holder: the explosion-proof D12 installs in classified areas, and the F12 family covers both schemes — the F12iS is intrinsically safe and loop-powered, the F12/D line-powered with display and datalogger. Intrinsic safety depends on the right barrier and wiring on your side. Use the input form to tell us the Class / Division or Zone and gas group and the transmitter, holder and documentation are specified to suit.
- Build the sampling train for a wet or remote stream — gas that will not reach the sensor on its own needs help: the A21 diaphragm pump draws a sample from a duct or remote point and alarms on loss of flow, and the C21 Dri-Gas dehumidifies it so a saturated stream does not blind the cell; for a permanently wet stream the B12 Wet uses sensors rated for 100% RH. Use the input form to tell us the stream temperature, humidity and distance and the sampling train is built around it.
- Size the controller to points and distance — match the readout tier to how many points you have and how far they sit: the B14 receiver handles one 4–20 mA point up to 10,000 ft; the A14/A11 modular system distributes display, relay and analog modules with sensors up to 1,000 ft; and the GasSens Midi networks up to 64 sensors over CANbus, to 1,024 points with Modbus. One point or a few → B14; a mid-size relay/analog system → A14/A11; a large networked plant → Midi.
To spec the right D12 gas transmitter:
Use the input form to tell us the target gas and its range, the background atmosphere, the area classification, and how many points you need to watch — and we’ll spec the sensor chemistry, transmitter, holder and controller for your application.
Gas Detection Application Sheet ›Talk to an engineer directly — Scott Prater, Principal · 917-580-0878 · scott@pratertechnical.com
Specifications compiled by Prater Technical Partners from Badger Meter ATi / GasSens gas-detection product literature.