Description
Product Introduction
The Yokogawa AALR121-S00 is a high-density, 16-channel RTD input card engineered for Yokogawa CENTUM VP and CS 3000 Distributed Control Systems (DCS). Serving as a direct sensor interface module, it eliminates the need for external head-mounted temperature transmitters by converting signals directly from 2-wire, 3-wire, or 4-wire resistance temperature sensors into digital control data across the DCS backplane.
Featuring galvanic isolation between individual channels, the AALR121-S00 protects sensitive central processing units from ground loops, common-mode noise, and field wiring surges commonly encountered across multi-zone thermal processes.
Key Technical Specifications
| Parameter | Specification / Value |
| Manufacturer | Yokogawa Electric Corporation |
| Part Number | AALR121-S00 |
| System Architecture | CENTUM VP / CENTUM CS 3000 (FIO Subrack) |
| Number of Inputs | 16 Channels (Channel-to-Channel Isolated) |
| Supported RTD Types | Pt100, JPt100, Cu100, Ni100, Resistance (0\ \Omega to 2000\ \Omega) |
| Wiring Connection | 2-wire, 3-wire, or 4-wire RTD configuration |
| Isolation Voltage | 500V AC between channels / 1500V AC between field and system |
| Conversion Accuracy | \pm 0.1\% of Full Scale |
| Power Consumption | Maximum 350 mA at 5V DC (supplied via backplane) |
| Operating Temp | -20°C to +70°C |
Application Scenarios & The “Trench” Experience
Picture a large multi-stage distillation column or polymerization reactor fitted with dozens of 3-wire Pt100 temperature sensors. An aging RTD input card develops an internal reference drift on channel 4, causing erratic temperature spikes in the control room and triggering false thermal alarms that threaten a plant shutdown. Swapping in a pre-tested Yokogawa AALR121-S00 module re-establishes exact resistance sampling, eliminating false alarms and restoring stable, closed-loop cascade temperature control instantly.
Primary Field Applications:
- Chemical & Petrochemical Processing: Multi-point temperature monitoring across reactors, distillation towers, and heat exchangers.
- Power Generation Facilities: Generator stator winding, bearing oil, and turbine casing temperature acquisition.
- Pharmaceutical & Fine Chemical Production: High-accuracy batch reactor jacket and vessel temperature loops.
AALR121-S00
AALR121-S00
Transparency SOP: Quality Assurance & Testing
Temperature input modules dictate process quality and safety thresholds. Every Yokogawa AALR121-S00 module undergoes a rigorous 5-step hardware qualification procedure before entering shippable inventory:
- Inbound Visual & Structural Check: Comprehensive inspection of edge connectors, guide rails, terminal shield plating, and onboard component integrity.
- Backplane Boot & Node Diagnostics: Mounting the module into a live CENTUM VP test node (RIO/FIO subrack) to verify 5V DC power-up handshakes and status LED diagnostics.
- 16-Channel Isolation & Linearity Test: Verifying channel-to-channel galvanic isolation and testing ADC response curves using precision decade resistance boxes across 2-wire and 3-wire modes.
- Multi-Point Temperature Calibration Sweep: Simulating Pt100 resistance values equivalent to -50^\circC, 0^\circC, 100^\circC, and 300^\circC across all 16 channels to confirm accuracy within \pm 0.1\% FS.
- ESD Cleaning & Protective Packaging: Contact restoration, anti-static vacuum wrapping, and high-density foam shipping protection.
The Veteran’s Tech Trap Guide (Crucial Value-Add)
- ⚠️ AALR121 (RTD) vs. AAT141 (Thermocouple): The AALR121 measures resistance (Pt100, \Omega), whereas thermocouple modules (like the AAT141) measure millivolts (mV). Installing an RTD module in a slot assigned for thermocouple signals will cause channel error alarms and invalid process readings in the DCS.
- ❗ Verify 3-Wire Lead Resistance Balancing: When using 3-wire Pt100 RTDs, ensure all three copper conductors have identical resistance. Mismatched lead wire lengths or loose screw terminals will introduce offset errors directly into the temperature calculation (1\ \Omega wire resistance mismatch causes approximately a 2.5^\circC reading error on Pt100!).
- ⚠️ Terminal Block & Cable Selection: The AALR121 pairs with dedicated terminal blocks (e.g., KS1 screw terminal blocks). Ensure terminal connections are clean and free of copper oxidation, which adds parasitic series resistance to the measurement loop.
- ❗ Check System Builder Module Type Setting: When replacing or adding an AALR121-S00 card, verify in CENTUM System Builder that each channel is properly configured for the correct RTD curve (e.g., IEC Pt100 vs. JIS JPt100) and wiring type (2-wire vs. 3-wire).
Frequently Asked Questions (FAQ for Conversion)
Q: Is the Yokogawa AALR121-S00 hot-swappable in a running CENTUM rack?
A: Yes, Yokogawa FIO modules support hot-swapping under power. However, ensure that control loops depending on those 16 temperature channels are placed in manual mode or bypassed before removing the card.
Q: Does the AALR121-S00 support 4-wire RTDs?
A: Yes, the module can be configured to support 2-wire, 3-wire, or 4-wire RTD sensors depending on the terminal block wiring and software channel configuration.
Q: What is the difference between AALR121-S00 and AALR121-S50?
A: The -S00 variant is the standard non-explosion-proof module for general cabinet areas, whereas the -S50 variant includes intrinsic safety / hazardous area approvals for direct field hazardous zone compliance.
Q: What warranty is provided with this surplus Yokogawa module?
A: Every Yokogawa AALR121-S00 module supplied from our inventory carries a full 12-month direct replacement warranty.
Q: Why purchase new surplus or refurbished AALR121 modules instead of ordering direct from Yokogawa?
A: OEM factory lead times for specialized DCS cards can take several months. Sourcing verified surplus or refurbished inventory resolves emergency outages immediately while maintaining 100% OEM hardware compatibility.
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