Siemens simatic S7-200. Product Information

Product Information

SIMATIC S7-200

EM231, EM232, EM235 Analog Input and Output Modules

Release

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selecting File " Print from the menu.

New Expansion Modules Available

The following expansion modules have been added to the S7-200 family. The order

numbers for these expansion modules are shown below:

S EM231 Analog Input AI 4 x 12 Bits

(order number 6ES7 231-0HC20-0XA0)

S EM232 Analog Output AQ 2 x 12 Bits

(order number 6ES7-232-0HB20-0XA0)

S EM235 Analog Combo AI 4/AQ 1 x 12 Bits

(order number 6ES7 235-0KD20-0XA0)

The technical specifications for the expansion modules are included in this product

information document. You can refer to the S7-200 Programmable Controller System

Manual for more information about the S7-200 product family.

Additional Assistance

For assistance in answering technical questions, for training on this product, or for

ordering, contact your Siemens distributor or sales office.

Description

EM231 Analog Input

EM232 Analog Output

EM235 Analog Combo

Order Number

AI 4 x 12 Bits

AQ 2 x 12 Bits

AI 4/AQ 1 x 12 Bits

6ES7 231-0HC20-0XA0

6ES7 232-0HB20-0XA0

6ES7 235-0KD20-0XA0

Input Specifications

Output Specifications

Input Specifications

Output

Specifications

General Specifications

Dimensions (W x H x D)

71.2 mm x 80 mm x 62 mm

46 mm x 80 mm x 62 mm

71.2 mm x 80 mm x 62 mm

Weight

183 g

148 g

186 g

Power loss (dissipation)

2 W

Number of physical I/O

4 analog input points

2 analog output points

4 analog input points,

1 analog output point

Power Consumption

From +5 VDC (from I/O

20 mA

30 mA

bus)

From L+

60 mA

70 mA (with both outputs at 20

60 mA (with output at 20 mA)

mA)

L+ voltage range,

20.4 to 28.8

Class 2 or DC sensor

supply

LED indicator

24 VDC Power Supply

24 VDC Power Supply Good,

Good,

ON = no fault,

OFF = no 24 VDC power

Analog Input Specifications

No. of Analog Input

Points

Isolation (Field side to

None

logic circuit)

Input type

Differential

Input ranges

Voltage (unipolar)

0 to 10 V, 0 to 5 V

0 to 10 V, 0 to 5 V,

0 to 1 V, 0 to 500 mV,

0 to 100 mV, 0 to 50 mV

Voltage (bipolar)

±5 V, ± 2.5 V

± 10 V, ± 5 V, ± 2.5 V,

± 1 V, ± 500 mV,

± 250 mV, ± 100 mV,

± 50 mV, ± 25 mV

Current

0 to 20 mA

Input Resolution

see Table 1

see Table 2

Voltage (unipolar)

Voltage (bipolar)

Current

Analog to digital

< 250 µs

conversion time

Analog input step

1.5 ms to 95%

response

Common mode rejection

40 dB, DC to 60 Hz

Common mode voltage

Signal voltage plus

common mode voltage

(must be ≤ 12 V)

Data word format

(see Figure 3)

Bipolar, full-scale range

-32000 to +32000

Unipolar, full-scale

0 to 32000

range

Input impedance

≥10 MΩ

≥ 10 MΩ

Input filter attenuation

-3 db @ 3.1 Khz

Maximum input voltage

30 VDC

Maximum input current

32 mA

Resolution

12 bit A/D converter

Description

EM231 Analog Input

EM232 Analog Output

EM235 Analog Combo

Order Number

AI4x12 Bits

AQ2x12 Bits

AI4/AQ 1 x 12 Bits

6ES7 231-0HC20-0XA0

6ES7 232-OHB20-0XA0

6ES7 235-0KD20-0XA0

Input Specifications

Output Specifications

Input Specifications

Output

Specifications

Analog Output Specifications

No. of Analog Output

Points

Isolation (Field side to

None

logic circuit)

Signal range

Voltage output

± 10 V

Current output

0 to 20 mA

Resolution, full-scale

Voltage

12 bits

Current

11 bits

Data word format

Voltage

-32000 to +32000

Current

0 to +32000

Accuracy

Worst case, 0° to 55° C

Voltage output

± 2% of full-scale

Current output

± 2% of full-scale

Typical, 25° C

Voltage output

± 0.5% of full-scale

Current output

± 0.5% of full-scale

Settling time

Voltage output

100 µS

Current output

2 mS

Maximum drive

Voltage output

5000 Ω minimum

Current output

500 Ω maximum

EM231

EM232

Current transmitter

Voltage transmitter

+ -

Unused input

Not used

RA A+ A - RB B+ B - RC C+ C-

RD D+

D-

EM232

EM231

AQ 2 x 12 Bit

AI 4

M L+

Gain

Configuration

M L+

24V

Not used

24 VDC power and

common terminals

EM235

Current transmitter

Voltage transmitter

+ -

Unused input

RA A+ A - RB B+ B - RC C+ C-

RD D+

D-

EM235

AI 4/AQ 1

M L+

Gain

Offset

Configuration

24V

24 VDC power and

common terminals

Figure 1

Connector Terminal Identification for Expansion Modules EM231, EM232, and EM235

Input Calibration

The calibration adjustments affect the instrumentation amplifier stage that follows the

analog multiplexer (see Figure 4). Therefore, calibration affects all user input channels.

Variations in the component values of each input circuit preceeding the analog

multiplexer will cause slight differences in the readings between channels connected to

the same input signal even after calibration.

To meet the specifications contained in this data sheet, you should enable analog input

filters for all inputs of the module. Select 64 or more samples in calculating the

average value. For more information about analog input filters, see the S7-200

Programmable Controller System Manual.

To calibrate the input, use the following steps.

1. Turn off the power to the module. Select the desired input range.

2. Turn on the power to the CPU and module. Allow the module to stabilize for 15

minutes.

3. Using a transmitter, a voltage source, or a current source, apply a zero value signal

to one of the input terminals.

4. Read the value reported to the CPU by the appropriate input channel.

5. Adjust the OFFSET potentiometer until the reading is zero, or the desired digital

data value.

6. Connect a full-scale value signal to one of the input terminals. Read the value

reported to the CPU.

7. Adjust the GAIN potentiometer until the reading is 32000, or the desired digital data

value.

8. Repeat OFFSET and GAIN calibration as required.

Calibration and Configuration Location for EM231 and EM235

The calibration potentiometer and configuration DIP switches are located on the right

of the bottom terminal block of the module, as shown in Figure 2.

EM231

↑ On

↓ Off

DIP

ON ↑

Fixed Terminal Block

Gain

Configuration

EM235

↑ On

↓ Off

DIP

ON ↑

Fixed Terminal Block

Gain Offset

Configuration

Figure 2

Calibration Potentiometer and Configuration DIP Switches for EM231 and EM235

Configuration for EM231

Table 1 shows how to configure the EM231 module using the configuration DIP

switches. Switches 1, 2, and 3 select the analog input range. All inputs are set to the

same analog input range. In this table, ON is closed, and OFF is open.

Table 1

EM231 Configuration Switch Table to Select Analog Input Range

Unipolar

Full-Scale Input

Resolution

SW1

SW2

SW3

OFF

0 to 10 V

2.5 mV

0 to 5 V

1.25 mV

OFF

0 to 20 mA

5 µA

Bipolar

Full-Scale Input

Resolution

SW1

SW2

SW3

OFF

± 5 V

2.5 mV

OFF

± 2.5 V

1.25 mV

Configuration for EM235

Table 2 shows how to configure the EM235 module using the configuration DIP

switches. Switches 1 through 6 select the analog input range and resolution. All inputs

are set to the same analog input range and format. Table 3 shows how to select for

unipolar/bipolar (switch 6), gain (switches 4 and 5), and attenuation (switches 1, 2, and

3). In these tables, ON is closed, and OFF is open.

Table 2

EM235 Configuration Switch Table to Select Analog Input Range and Resolution

Unipolar

Full-Scale Input

Resolution

SW1

SW2

SW3

SW4

SW5

SW6

OFF

0 to 50 mV

12.5 mV

OFF

0 to 100 mV

25 mV

OFF

0 to 500 mV

125 mV

OFF

0 to 1 V

250 mV

OFF

0 to 5 V

1.25 mV

OFF

0 to 20 mA

5 mA

OFF

0 to 10 V

2.5 mV

Bipolar

Full-Scale Input

Resolution

SW1

SW2

SW3

SW4

SW5

SW6

OFF

+25 mV

12.5 mV

OFF

+50 mV

25 mV

OFF

+100 mV

50 mV

OFF

+250 mV

125 mV

OFF

+500 mV

250 mV

OFF

+1 V

500 mV

OFF

+2.5 V

1.25 mV

OFF

+5 V

2.5 mV

OFF

+10 V

5 mV

Table 3

EM235 Configuration Switch Table to Select Unipolar/Bipolar, Gain, and

Attenuation

EM235 Configuration Switches

Unipolar/Bipolar

Attenuation

Gain Select

SW1

SW2

SW3

SW4

SW5

SW6

Select

Unipolar

OFF

Bipolar

OFF

x10

OFF

x100

invalid

OFF

0.8

OFF

0.4

OFF

0.2

Input Data Word Format for EM231 and EM235

Figure 3 shows where the 12-bit data value is placed within the analog input word of

the CPU.

MSB

LSB

AIW XX

Data value12 Bits

Unipolar data

MSB

LSB

AIW XX

Data

value

12 Bits

Bipolar data

Figure 3

Input Data Word Format for EM231 and EM235

Note

The 12 bits of the analog-to-digital converter (ADC) readings are left-justified in the

data word format. The MSB is the sign bit: zero indicates a positive data word value.

In the unipolar format, the three trailing zeros cause the data word to change by a

count of eight for each one-count change in the ADC value. In the bipolar format, the

four trailing zeros cause the data word to change by a count of sixteen for each one

count change in the ADC value.

Input Block Diagram for EM231 and EM235

Figure 4 shows the EM231 and EM235 input block diagrams.

A+

EM231

Rloop

A-

GAIN ADJUST

A=1

B+

Instrumentation

AMP

BUFFER

Rloop

A/D Converter

B-

A=2

C+

Rloop

C-

A=3

D+

Rloop

D-

A=4

Input filter

MUX 4 to 1

EM235

A+

Rloop

A-

GAIN ADJUST

A=1

B+

Analog-to-digital converter

Instrumentation

AMP

BUFFER

Rloop

A/D Converter

B-

A=2

DATA

C+

REF_VOLT

Rloop

Buffer

C-

A=3

Offset Adjust

D+

Rloop

D-

A=4

Input filter

MUX 4 to 1

Figure 4

EM231 and EM235 Input Block Diagram

Output Data Word Format for EM232 and EM235

Figure 5 shows where the 12-bit data value is placed within the analog output word of

the CPU.

MSB

LSB

AQW XX

Data value

11 Bits

Current output data format

MSB

LSB

AQW XX

Data

value

12 Bits

Voltage output data format

Figure 5

Output Data Word Format for EM232 and EM235

Note

The 12 bits of the digital-to-analog converter (DAC) readings are left-justified in the

output data word format. The MSB is the sign bit: zero indicates a positive data word

value. The four trailing zeros are truncated before being loaded into the DAC

registers. These bits have no effect on the output signal value.

Output Block Diagram for EM232 and EM235

Figure 6 shows the EM232 and EM235 output block diagrams.

+24 Volt

100

Voltage-to-current converter

Iout

0..20 mA

Vref

D/A converter

+/- 2V

Vout

-10.. +10 Volts

DATA

Digital-to-analog converter

1/4

Voltage output buffer

Figure 6

EM232 and EM235 Output Block Diagram

Installation Guidelines

Use the following guidelines to ensure good accuracy and repeatability:

S Ensure that the 24-VDC Sensor Supply is free of noise and is stable.

S Use the shortest possible sensor wires.

S Use shielded twisted pair wiring for sensor wires.

S Terminate the shield at the Sensor location only.

S Short the inputs for any unused channels, as shown in Figure 1.

S Avoid bending the wires into sharp angles.

S Use wireways for wire routing.

S Avoid placing signal wires parallel to high-energy wires. If the two wires must meet,

cross them at right angles.

S Ensure that the input signals are within the common mode voltage specification by

isolating the input signals or referencing them to the external 24V common of the

analog module.

Note

The EM231 and EM235 expansion modules are not recommended for use with

thermocouples.

Understanding and Using the Analog Input Module: Accuracy and Repeatability

The EM231 and EM235 analog input modules are low-cost, high-speed 12 bit analog

input modules. The modules are capable of converting an analog input to its

corresponding digital value in 149 µsec. Conversion of the analog signal input is

performed each time the analog point is accessed by your program. These times must

be added to the basic execution time of the instruction used to access the analog

input.

The EM231 and EM235 provide an unprocessed digital value (no linearization or

filtering) that corresponds to the analog voltage or current presented at the module’s

input terminals. Since the modules are high-speed modules, they can follow rapid

changes in the analog input signal (including internal and external noise).

Reading-to-reading variations caused by noise for a constant or slowly changing

analog input signal can be minimized by averaging a number of readings. As the

number of readings used in computing the average value increases, a correspondingly

slower response time to changes in the input signal can be observed.

The specifications for repeatability describe the reading-to-reading variations of the

module for an input signal that is not changing. The repeatability specification defines

the limits within which 99% of the readings will fall. The mean accuracy specification

describes the average value of the error (the difference between the average value of

individual readings and the exact value of the actual analog input signal). The

repeatability is described in Figure 7 by the bell curve. This figure shows the 99%

repeatability limits, the mean or average value of the individual readings, and the mean

accuracy in a graphical form. Table 4 gives the repeatability specifications and the

mean accuracy as they relate to each of the configurable ranges.

Average

Signal

Value

Input

Mean (average)

Accuracy

Repeatability limits

(99% of all readings fall within these limits)

Figure 7

Accuracy Definitions

Table 4

EM231 and EM235 Specifications

Repeatability1

Mean (average) Accuracy1,2,3,4

Full Scale Input Range

% of Full Scale

Counts

% of Full Scale

Counts

EM231 Specifications

0 to 5 V

0 to 20 mA

± 24

± 0.01%

0 to 10 V

± 0.075%

± 32

± 2.5 V

0.05%

± 5 V

EM235 Specifications

0 to 50 mV

± 0.25%

± 80

0 to 100 mV

± 0.2%

± 64

0 to 500 mV

0 to 1 V

± 0.075%

± 24

0 to 5 V

± 0.05%

± 16

0 to 20 mA

0 to 10 V

± 25 mV

± 0.25%

± 160

± 50 mV

± 0.2%

± 128

± 100 mV

± 0.1%

± 64

± 250 mV

± 500 mV

± 0.075%

± 48

± 1 V

0.05%

± 2.5 V

± 5 V

± 10 V

Measurements made after the selected input range has been calibrated.

The offset error in the signal near zero analog input is not corrected, and is not included in the accuracy specifications.

There is a channel-to-channel carryover conversion error, due to the finite settling time of the analog multiplexer. The

maximum carryover error is 0.1% of the difference between channels.

Mean accuracy includes effects of non-linearity and drift from 0 to 55 degrees C.

Definitions of the Analog Specifications

S Accuracy: deviation from the expected value on a given point.

S Resolution: the effect of an LSB change reflected on the output.

Agency Standards

These modules adhere to the following agency standards: UL 508 Listed (Industrial

Control Equipment); CSA C22.2 Number 142 Certified (Process Control Equipment);

FM Class I, Division 2, Groups A, B, C, & D Hazardous Locations, T4A; VDE 0160:

Electronic equipment for use in electrical power installations; European Community

(CE) Low Voltage Directive 73/23/EEC, EN 61131-2: Programmable controllers -

Equipment requirements; European Community (CE) EMC Directive 89/336/EEC.

For more information about these standards, refer to the S7-200 Programmable

Controller System Manual.

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