Product Overview
The ATi B12 is the economical, loop-powered fixed gas point in the ATi line — a two-wire transmitter that draws its power from the 4–20 mA loop and returns a current linearly proportional to gas concentration in ambient air. One B12 chassis accepts an electrochemical sensor for any of roughly thirty toxic and reactive gases — chlorine, ammonia, H₂S, ozone, CO, hydrogen, the hydrogen halides and the semiconductor hydrides among them — so the same transmitter covers a plant by sensor choice rather than a model per gas. It keeps the electronics deliberately spare: concentration in, 4–20 mA out, with display, setpoints and relays handled at the B14 receiver or an existing PLC/DCS. A NEMA 4X polystyrene housing is standard, with an explosion-proof Class I, Division 1 option for classified areas. For a permanently wet stream — a wet-scrubber outlet, a chlorine storage vent — the B12 Wet variant swaps in a corrosion-resistant sensor rated for 100% relative humidity (see Variants).
Typical Installation
One platform, two sensor sets
The B12 is one loop-powered two-wire transmitter; the sensor set decides where it can read. The standard B12 uses diffusion sensors for clean ambient air; the B12 Wet carries a corrosion-resistant sensor rated for 100% relative humidity so it survives a moisture-saturated stream that would blind an ordinary diffusion sensor. Same transmitter and 4–20 mA loop — pick the sensor set by how wet the stream is.
B12
standard diffusion sensors
- ~30 toxic and reactive gases, ppb to ppm by sensor choice
- Gas-specific electrochemical sensor; close-coupled, remote (25 ft) or duct-insertion
- NEMA 4X polystyrene standard; explosion-proof Class I, Div 1, Groups B/C/D option
B12 Wet
corrosion-resistant 100% RH sensors
- Oxidant gases (Cl₂, Br₂, ClO₂, O₂) and acid gases (HCl, HF) at 0–10 / 20 / 50 / 100 ppm, plus hydrogen at 0–2% or 0–10%
- Noryl sensor rated for 100% RH — direct stack-insertion (1-1/4″ MNPT) or flow-through for wet-scrubber outlets and chlorine storage
- 25 ft sensor cable standard (100 ft max); 12–28 VDC; 0 to 50°C operating
Both are the same two-wire, loop-powered B12 transmitter returning a 4–20 mA signal into a PLC, DCS or the B14 receiver, with the same potentiometer zero/span calibration and the optional LCD on the NEMA 4X builds — only the sensor set (standard diffusion vs. 100% RH wet-stack) differs.
Key Features & Benefits
- The low-cost fixed point that still covers ~30 gases — one two-wire transmitter chassis takes a sensor for any of about thirty toxic and reactive gases, so a plant standardizes on the B12 and stocks the sensor that matches each point. Coverage without a separate model number per gas.
- Two wires do power and signal — the 4–20 mA loop carries both the supply and the measurement, so a single twisted pair runs the point — and at 12 VDC it will run on battery power where mains is not available. Less wire, fewer terminations, a point you can put on a UPS.
- Put the sensor where the gas is — close-couple the sensor to the box, separate it on a 25 ft cable, or insert it into a duct — the reading happens where the leak collects, not just where the enclosure mounts. Mount for access, sense for detection.
- Hand the alarm logic to the receiver — the transmitter stays simple — concentration in, 4–20 mA out — and the B14 receiver adds display, setpoints and relays, or the signal ties straight into an existing PLC or DCS. Buy alarm channels once, at the panel, not at every sensor.
Specifications
- Detection principle
- Electrochemical sensing, matched to the gas — the B12 is a loop-powered diffusion transmitter whose 4–20 mA output tracks the measured concentration over the sensor’s range. The B12 Wet variant carries a sensor built for moisture-saturated streams (see Variants).
- Target gases
- Roughly 30 toxic and reactive gases — chlorine, ammonia, hydrogen sulfide, ozone, chlorine dioxide, carbon monoxide, hydrogen, oxygen, phosgene, nitric oxide, NO₂, SO₂, the hydrogen halides (HCl, HF, HCN), ethylene oxide, formaldehyde, hydrogen peroxide, and the semiconductor hydrides (arsine, diborane, germane, hydrogen selenide, phosphine, silane).
- Measuring range
- Per sensor and field-coded — from 0–1 ppm (chlorine, bromine, fluorine, chlorine dioxide) and 0–1000 ppb (arsine, diborane, germane, phosphine) up to 0–2000 ppm, with 0–10% hydrogen and 0–30% O₂ at the top of their ranges; the standard range for each gas ships unless another is ordered.
- Sensor (H-Series smart module)
- Close-coupled to the enclosure as standard, or remote on a 25 ft cable for special applications; duct-insertion adapters and flow cells are available where the gas must be drawn to the sensor rather than reaching it by diffusion.
- Accuracy / repeatability
- Generally ±5% of value (limited by the available calibration-gas accuracy), with electronic repeatability ±1% and linearity ±0.5% of full scale. Zero drift is sensor-dependent but generally under 2% of full scale per month, non-cumulative.
- Outputs
- Loop-powered 4–20 mA, driving up to 675 Ω at 24 VDC (less at lower supply voltages — the load follows the input voltage). The two-wire signal ties straight into a PLC, DCS or the B14 alarm receiver; alarm relays live in the receiver, not the transmitter.
- Sensor holder / mounting options
- Enclosure choices set the holder: NEMA 4X polystyrene close-coupled, NEMA 4X with the sensor separated on a 25 ft cable, or duct-insertion with the duct adapter — each available with or without the integral LCD.
- Area classification
- NEMA 4X polystyrene as standard; an explosion-proof enclosure rated Class I, Division 1, Groups B, C, D is the option for classified areas (the LCD is not offered with the explosion-proof build).
- Power
- Loop-powered 12–30 VDC; operable at 12 VDC with a reduced output load for battery-powered installations, or at 24 VDC for the full 675 Ω drive.
- Display
- Optional 3-digit LCD for local concentration readout — available on the NEMA 4X builds only, not with the explosion-proof enclosure.
- Operating temperature / humidity
- –30 to 55°C (–22 to 131°F) for most gases; oxygen sensors run –10 to 55°C. Sensor pressure limits are 7–30 PSIA (0.5–2 bar).
- Calibration
- Zero and span are set on potentiometers on the transmitter board; calibration adapters slide onto the standard or explosion-proof sensors so gas can be applied without removing the unit.
- Dimensions / mounting
- Roughly 0.25 lb (0.12 kg) in the NEMA 4X polystyrene housing, rising to 1.75 lb (0.8 kg) with the cast explosion-proof enclosure.
Common Applications
- Water and wastewater disinfection — chlorine, chlorine dioxide and ozone leak detection at storage and feed rooms
- Wet scrubber outlets and chlorine storage — B12 Wet for moisture-saturated oxidant and acid-gas streams
- Semiconductor and specialty-gas handling — ppb-level arsine, diborane, germane, phosphine and silane monitoring
- Refrigeration and cold storage — ammonia exposure monitoring in machinery rooms
- Battery rooms and process buildings — hydrogen, CO and acid-gas point monitoring on a single loop
The B12 is the economical loop-powered toxic point. Where the stream is wet, the B12 Wet variant on this page is the answer; for a classified-area, full-feature unit with on-board relays and HART/Modbus see the D12, for combustible %LEL the C12-17, and to display and alarm the loop the B14 receiver.
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 B12 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.