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STAHL 946012-08-11
Model: 946012-08-11 (catalogued as 9460/12-08-11, AIM 08)
Product Name: Intrinsic Safety Analog Input Module
Product Introduction: This module acquires 4-20 mA or 0-20 mA transmitter signals from hazardous-area field instruments and converts them into digital values for IS1+/System 9400 remote I/O. It is designed for analog signal isolation, HART transparency and short/open-wire detection in explosive atmospheres.
Detailed content
Technical Specifications:
- Channels: 8 analog inputs; 3-wire/4-wire transmitters or active sources occupy two channels each
- Signal Range: 0-20 mA and 4-20 mA, per-channel configurable
- Maximum Input: 23.5 mA
- Transmitter Excitation: 16.0 V at 20 mA for 2-wire/3-wire loop power
- Input Resistance for Active Source: 14 Ω
- Resolution: 12.75 bit at small filter, 14.75 bit at medium/50 Hz/60 Hz filter in 4-20 mA range
- Accuracy: 0.075% span at small filter, 0.05% span at medium/50 Hz/60 Hz filter, 23°C reference
- Filter Time Constants: Small, medium and long; maximum input-to-bus delay 32 ms/120 ms/840 ms according to filter
- Galvanic Isolation: 1500 V AC supply/system, 500 V AC between modules, 500 V AC input/system
- Intrinsic Safety Entity Output: 26.2 V open circuit, 86 mA short circuit, 561 mW for 2-wire/3-wire; 0 V/0 mA for 4-wire active source entity option shown in safety table
- Cable Parameters IIC: 97 nF capacitive, 2.71 mH inductive; IIB 0.75 μF capacitive per documented entity limits
- Operating Temperature: Use within STAHL IS1+ station environmental limits; typical module documentation supports industrial hazardous-area ambient ranges
Functional Features:
- HART Transparency: Digital communication pass-through with HART field devices
- Per-Channel Diagnostics: Open-circuit, short-circuit, over-range, under-range, configuration mismatch
- Adjustable Fault Action: Substitute value, alarm code or hold-last-value on wire fault
- LED Indication: Green RUN, red ERR
Application Scenarios:
- Refining and Petrochemical: Pressure, flow and level 4-20 mA transmitters in Zone 1/Zone 2
- Offshore Modules: IS1+ stations on press platforms and utility skids
- Chemical Reactors: Temperature, pH and analytical analog signals with Ex i isolation
- Pharmaceutical and Specialty Chemicals: Validated analog acquisition with audit-friendly diagnostics
Structural Characteristics:
- Mounting: IS1+ remote I/O BusRail or System 9400 backplane per station configuration
- Terminals: Plug-in field terminals for transmitter loops
- Housing: STAHL IS1+ modular enclosure compatible with adjacent I/O modules
Working Principle: Each channel powers or receives the analog loop, conditions the current signal, performs A/D conversion and transmits digitized values to the CPU module. HART FSK data is passed without degrading the 4-20 mA value. Entity parameters limit voltage, current and power so field circuits remain intrinsically safe.
Installation Requirements:
- Verify Ex entity compatibility between transmitter, cable capacitance/inductance and module parameters.
- Use shielded cable; connect shield to the IS1+ station earth concept, not randomly at field devices.
- Do not ground intrinsic safety field circuits unless the approved loop design requires it.
- Configure range, filter and fault response before commissioning.
Usage Precautions:
- Do not mix 2-wire loop-powered and 4-wire active sources on the same channel without correct configuration.
- Replace with identical STAHL AIM variant and firmware class to avoid BusRail configuration alarms.
- Check for 21 mA+ saturation, 3.6 mA- underrange or 0 mA open-loop symptoms before assuming module failure.
