6ES7-235-0KD22-0XA0 Siemens

Detailed Explanation of EM 235 Analog I/O Module

1. Model Code Breakdown

2. Core Technical Specifications

Posicionamiento del producto: Expansion module for SIMATIC S7-200 series, only compatible with S7-22X CPUs (not compatible with S7-21X), spare part

Configuración de E/S: 4 entradas analógicas (AI) + 1 salida analógica (HACIA)

Características de entrada:

Signal type: Differential input, ±10V DC (other ranges selectable via DIP switches)

Resolution: 12 bits (including sign bit)

Input impedance: ≥10MΩ (voltage input)

Protección contra sobretensión: Up to 30V DC

Características de salida:

Signal type: ±10V DC (Voltaje) / 0–20mA (actual, opcional)

Resolution: 12 bits for voltage output, 11 bits for current output

Output impedance: ≤0.5Ω (voltage output)

Load capacity: Max 5mA for voltage output, max 20mA for current output

Requisitos de energía:

External supply: 24En DC, max 60mA

Backplane bus: 5En DC, max 30mA

Power dissipation: Typical 2W

Conversion Performance:

Input conversion time: <250μs per channel

Output response time: 1.5ms to 95% steady-state value

3. Entorno operativo
4. Temperatura de funcionamiento: 0–60°C (horizontal mounting), 0–40°C (vertical mounting)
5. Storage temperature: -40–+85°C
6. Humedad relativa: 5–95% (non-condensing)
7. Clase de protección: IP20 (Cumple con IEC 61131-2)
8. Montaje: Montaje en carril DIN (compliant with EN 50022)
9. Application scenarios:

Analog signal acquisition and control for small automation systems

Monitoring and regulation of process variables such as temperature, presión, and flow

Simple control loops requiring simultaneous analog input and output

4. Reemplazo & Compatible Models

5. Official Ordering Information

Standard order number: 6ES7 235-0KD22-0XA0 (global version)

China order number: 6ES7 235-0KD22-0XA8 (EM 235 CN)

Product status: Currently a spare part for S7-200 system maintenance and replacement

6. Key Usage Notes
7. DIP switch settings: DIP switches on the side select input signal range; only one range can be set for the entire module
8. Programming:

Use Scale_I_to_R and Scale_R_to_I instructions in S7-200 software for analog/digital conversion

Analog input addresses: AIW0–AIW6 (2 bytes per channel)

Analog output address: AQW0 (2 bytes)

3. Wiring rules:

Use shielded twisted-pair cable for analog signals, keep at least 10cm away from power cables

Unused channels should be shorted to avoid interference

4. Precauciones:

Both external 24V DC and backplane 5V DC power must be connected

Hot swapping not supported; install/remove only with power off

7. Comparison with S7-200 SMART Modules

Complete Model List of Siemens EM 235 Analog I/O Modules

1. Core EM 235 Model Series (by hardware version)

2. Detailed Model Differences

2.1 Common Features of All EM 235 Models

I/O: 4AI + 1HACIA (3AI + 1AO for 00 versión)

Input: ±10V DC (other ranges via DIP switches: 0–20mA, 4–20mA, mV)

Producción: ±10V / 0–20mA (4–20mA via wiring)

Resolution: 12-bit input (with sign), 12-bit voltage output, 11-bit current output

Compatibilidad: Only for S7-22X CPUs (not S7-21X)

2.2 Diferencias clave

2.3 Global vs. Porcelana (CN) Version

6ES7 235-0KD22-0XA0: Global version, worldwide except China

6ES7 235-0KD22-0XA8: China-specific version; same functions and parameters, different certification and distribution

3. Realizar pedidos & Reemplazo

3.1 Current Valid Part Numbers

Global: 6ES7 235-0KD22-0XA0 (spare)

Porcelana: 6ES7 235-0KD22-0XA8 (EM 235 CN, spare)

3.2 Upgrade Path to S7-200 SMART

4. Important Operational Notes
5. DIP switches: Set uniform measurement range for all AI channels
6. Addressing:

Analog inputs: AIW0–AIW6 (2 bytes each)

Analog output: AQW0 (2 bytes)

3. Alambrado:

Shielded twisted-pair required; separate from power cables by ≥10cm

Short unused channels to reduce noise

4. Fuerza: Both 24V DC external and 5V DC backplane required; no hot-swapping

The core models of the Siemens EM 235 analog I/O module are 6ES7 235-0KD22-0XA0 (global) and 6ES7 235-0KD22-0XA8 (China CN), both hardware version 22 spare parts for S7-22X CPU maintenance. Earlier versions (00/10/20) are discontinued. For system upgrades, use corresponding S7-200 SMART modules.

Siemens EM 235 (4 entradas analógicas + 1 salida analógica)

is the most widely used analog mixed module for the S7-200 micro PLC.

Its core purpose: acquire multiple analog sensor signals and output one analog for closed-loop control.

It is designed for small-to-medium equipment, standalone automation, and local control systems, not large DCS systems.

Below is a complete list of applications by industry + typical control scenarios.

1. General Closed-Loop Control Applications
2. Constant Pressure Control

AI: Pressure transmitter (4–20mA)

HACIA: Inverter for pump/fan (0–10V or 0–20mA)

Uses: Constant pressure water supply, compressed air regulation, pipeline pressure stabilization

2. Constant Temperature Control

AI: Temperature transmitter, thermocouple/RTD

HACIA: Electric control valve, heater, electronic expansion valve

Uses: Water tank temperature control, small oven, HVAC unit, heat exchanger station

3. Constant Level Control

AI: Level transmitter (hydrostatic/ultrasonic)

HACIA: Inlet control valve, variable-speed drainage pump

Uses: Water tank, reservoir, water tower, small storage tank level maintenance

4. Flow & Metering Control

AI: Electromagnetic flowmeter, turbine flowmeter

HACIA: Control valve, metering pump, proportional valve

Uses: Batching systems, dosing, fluid proportioning

5. Tension & Position Control

AI: Tension sensor, displacement transducer

HACIA: Inversor, proportional hydraulic valve

Uses: Constant tension in textile, printing, film, cable machinery

2. Industry-Specific Applications

2.1 Water Supply & Wastewater Treatment

Small constant-pressure water supply systems

Sewage lift pumps, integrated wastewater treatment

Water tank level monitoring and auto refill

Pipeline pressure/flow monitoring and inverter control

2.2 climatización & Refrigeration

Chillers, air-cooled units

Fan coil units, air handling units

Heat exchanger station: primary/secondary water temp/pressure + valve control

Cooling tower fan speed control

2.3 Light Industry & Automation Machinery

Packaging, filling, sealing machines (level/weight control)

Small machine tools, hydraulic systems (presión + proportional valve control)

Conveyor speed adjustment, material height detection

Food machinery: mezcladores, blenders, oven temperature control

2.4 Small Chemical & Batching Systems

Temperature and pressure monitoring for small reactors

Liquid batching and proportional mixing

Dosing systems: metering pump flow control

Tank level and temperature remote monitoring

2.5 Environmental Equipment

Bag filter differential pressure + fan control

Small desulfurization and denitrification regulation

Exhaust fan and spray pump control

2.6 Automatización de edificios & Small Facilities

Building AHU and fresh air units

Ventilation pressure control in underground garages

Small heating and heat exchanger stations

2.7 Small Boilers & Heating Systems

Hot water boiler temperature, presión, level monitoring

Circulation pump variable-speed control

Analog control of burner damper/fuel valve

2.8 Hydraulic & Pneumatic Equipment

Hydraulic power unit pressure monitoring

Proportional pressure/flow valve control

Precision position control of pneumatic actuators

3. Ideal Project Characteristics for EM 235

Small system: 1 CPU + few expansion modules

Requires 2–4 analog inputs and 1 analog control output

Compact space, cost-sensitive

Standard industrial signals: 0–10V / 0–20mA / 4–20mA

Single closed-loop control (temperatura, presión, nivel, tension)

4. Summary of Typical Applications

The EM 235 is widely used in small automation machines, pump stations, HVAC units, constant-pressure water supply, and temperature control systems

where multi-channel analog acquisition plus single-channel analog closed-loop control is required.