Description
The Siemens 6ES7231-0HC22-0XA8 (and its export twin 6ES7231-0HC22-0XA0) is an EM 231 Analog Input expansion module for the SIMATIC S7-200 CN / S7-200 (CPU 221/222/224/224XP/226) PLC system. It provides 4 analog input channels (differential) supporting ±10 V DC, ±5 V DC, ±2.5 V DC, 0–20 mA, and 4–20 mA signals with 12-bit resolution + sign (13-bit total).
The 6ES7231-7PB22-0XA8 / 0XA0 is the EM 231 Thermocouple / RTD Input module — 4 channels capable of directly reading Thermocouple (J/K/T/E/S/R/B/N) and RTD (Pt100, Cu10, Ni100 etc.) with built-in Cold Junction Compensation (CJC) — NOT interchangeable with the -0HC22 voltage/current version!
Key points:
- 6ES7231-0HC22-0XA8 → S7-200 CN version (Chinese localized marking, fully compatible with standard S7-200 CPUs) — 4 AI (Voltage/Current), 12-bit+sign.
- 6ES7231-0HC22-0XA0 → Export / International version — electrically identical to -0XA8.
- 6ES7231-7PB22-0XA8 / 0XA0 → EM 231 TC/RTD Input — 4 ch TC/RTD — different functionality — use when temperature measurement is needed.
Modules snap onto the right side of the S7-200 CPU or previous expansion module and are configured in STEP 7-Micro/WIN (V4.x) via the “System Block → EM 231 Configuration”.
Key Features
- Inputs (0HC22): 4 × Differential Analog Inputs (Vin+/Vin- per ch) — Voltage ±10V/±5V/±2.5V or Current 0/4–20mA (via jumper or internal shunt — check DIP switch/DIP-less setting in Micro/WIN)
- Resolution (0HC22): 12 bits + sign (raw value range 0–32000 for unipolar / -32000 to +32000 for bipolar in Micro/WIN after scaling)
- Inputs (7PB22): 4 × TC or RTD inputs (direct wire to thermocouple or 2/3/4-wire RTD) — built-in CJC, 15-bit + sign typical for temp. modules
- Isolation: Optical isolation between S7-200 bus & analog circuitry (≥ 500 V AC)
- DIP Switches / Software Config: On -0HC22 newer revisions config is done in Micro/WIN System Block (older had DIP switches for range); -7PB22 is entirely software-configured (type of TC/RTD, C/F, etc.)
- Country of Origin: Germany / China (Siemens Global)
Model & Capability Table (S7-200 EM 231 Family)
Model | Input Type | Channels | Resolution | Direct TC/RTD? | Typical Use |
|---|---|---|---|---|---|
6ES7231-0HC22-0XA8 (CN) / 0XA0 | Voltage ±10V etc. / Current 0/4–20mA | 4 AI | 12-bit + sign (13-bit total) | ❌ No | Pressure/flow/level tx signals |
6ES7231-7PB22-0XA8 / 0XA0 | Thermocouple & RTD | 4 AI | 15-bit + sign (temp. mod.) | ✅ Yes (TC J/K/T/E/S/R/B/N; RTD Pt100 etc.) | Furnace/oven temp. monitoring |
6ES7231-0HF22-0XA0 | 8 AI Voltage/Current (rare) | 8 AI | 12-bit + sign | ❌ No | More analog points in one slot |
⚠️ CRITICAL Selection & Wiring Notes:
Technical Specifications (Representative — 6ES7231-0HC22-0XA8, 4 AI, ±10V/4–20mA, 12-bit+sign)
Parameter | Specification |
|---|---|
Model / Order Code | 6ES7231-0HC22-0XA8 (Siemens S7-200 CN EM 231 Analog Input 4×AI) |
Number of Channels | 4 differential analog inputs (grouped — common reference per pair on some; check terminal layout) |
Input Ranges (Software Selectable in Micro/WIN) | Voltage: ±10 V DC, ±5 V DC, ±2.5 V DC, 0–10 V DC (some via scaling); Current: 0–20 mA, 4–20 mA |
Resolution | 12 bits + sign (13-bit total including sign bit) — conversion time ~ 200–250 µs per channel in fast mode |
Data Format (Micro/WIN) | Unipolar: 0–32000 (0–20mA / 0–10V mapped); Bipolar: -32000 to +32000 (±10V / ±5V mapped) — user can apply scaling ITD or math to get engineering units |
Isolation (Bus ↔ Analog) | ≥ 500 V AC (optical) |
Backplane Current Draw (5V) | ~ 30 mA (typical) |
Front Connector | Built-in screw terminals (removable — 12-position typical for 4 AI + power ref.) |
Mounting | Snaps onto right side of S7-200 CPU or previous EM module (DIN rail or screw-mount) |
Dimensions (W×H×D) | 71.5 mm × 80 mm × 62 mm (standard S7-200 expansion width) |
Weight | ~ 0.2 kg |
Operating Temp. | 0 … +55 °C (horizontal) / 0 … +45 °C (vertical — check manual) |
Software | STEP 7-Micro/WIN V4.x (or later compatible — Chinese version V4_SPx also supports CN modules) |
Standards | CE, UL 508, cULus, FM (Cls I Div 2), RoHS |
Warranty & After-Sales
- Factory new units: 12 months warranty
- Refurbished units: 3-6 months warranty (analog loopback test on S7-200 test rig)
- Technical support for:
- EM 231 selection (-0HC22 for V/I signals vs -7PB22 for TC/RTD)
- STEP 7-Micro/WIN System Block configuration (range select per channel, DIP-less setup)
- Wiring best practices (shielded twisted pair, M terminal ground, separation from digital I/O cables)
- Scaling (using Math blocks or ITD + MUL/DIV to convert raw 0–32000 / -32000…+32000 to engineering units like °C, bar, psi)
- Troubleshooting (checking raw value in STATUS Chart, verifying jumper/DIP if old revision)
- Cross-reference S7-1200 SM 1231 if migrating from S7-200
Delivery Time
- Standard delivery: 3-5 working days (stock items)
- Express shipping available upon request
Why Choose Our Store
- Genuine Siemens S7-200 / S7-200 CN expansion modules — not re-badged clones with poor A/D linearity
- Global supply network with competitive pricing
- Expertise in S7-200 hardware configuration & analog signal conditioning (Micro/WIN scaling, shielding, grounding)
- Comprehensive technical documentation (terminal layout, Micro/WIN config screenshot, scaling example)
- Responsive customer service and support
Applications
- Process Signal Acquisition: Read 4–20 mA from pressure/flow/level transmitters into S7-200 for PID loops.
- Temperature Monitoring: With EM 231 -7PB22 — direct TC/RTD input (CJC built-in) for oven/furnace/bearing temp.
- Retrofit / Spare: Replace failed EM 231 in existing S7-200 panel — same article number = drop-in (transfer Micro/WIN System Block settings from PG).
- Machine Control: Small-to-medium machines using S7-200 — add analog sensing capability beyond CPU built-in (CPU 22x have NO analog built-in except rare 224XP with 2AI/1AO — this expands further).
- Test Benches: Capture analog process variables for quality verification.
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