show the entry list

S7-300 I/O Analog -- Setting up and parameterizing hardware -- Connecting and wiring modules 
What should you pay attention to when an RTD encoder with 4-conductor connection is connected to an to the SM331 analog input module? 
How should you connect and wire measuring transducers and M connections taking the example of the SM331 (6ES7331-7KF02-0AB0 and 6ES7331-1KF01-0AB0)? 
How do you connect a 2-wire measuring transducer to analog module 6ES7 331-1KF0.-0AB0, a compact CPU or a C7 device? 
How should you connect unused channels of analog input blocks? 
With the correct wiring, how can you avoid exceeding the common-mode voltage (Ucm) and subsequent measured value overflow or underflow in the analog input module 6ES7 331-1KF0.-0AB0? 
How should you deal with unused channels and wire break in the analog input module 6ES7 331-7PF01-0AB0? 
How can you avoid exceeding the common-mode voltage (Ucm) with the SM 331-7KB02/-7KF02 modules and subsequent measured value overflow or underflow? 
Why do you need a compensating box for connecting thermocouples to the analog modules SM331 (6ES7331-7KF02-0AB0 and 6ES7331-7KB02-0AB0) and how do you connect them? 
What should you watch out for with the supply of a 2-wire measuring transducer via the modules 6ES7331-7KF02-0AB0 and 6ES7331-7KB02-0AB0 with CPU switched off? 
How do you avoid the fluctuation in the analog inputs in the SM335 module (6ES7335-7HG01-0AB0)? 
With the correct wiring, how can you avoid exceeding the common-mode voltage (Ucm) and subsequent measured value overflow or underflow in the module 6ES7 334-0CE01-0AA0? 
How do you connect a potentiometer to the analog module 6ES7 331-1KF0.-0AB0 (resistance measuring)? 

What should you pay attention to when an RTD encoder with 4-conductor connection is connected to an to the SM331 analog input module?Go to beginning
Part number:

This entry describes how a RTD encoder (4-conductor connection) is linked to the following analog input blocks:

  • SM331 6ES7 331-1KF00-0AB0
  • SM331 6ES7 331-1KF01-0AB0
  • SM331 6ES7 331-1KF02-0AB0
  • SM331 6ES7 331-7KF00-0AB0
  • SM331 6ES7 331-7KF01-0AB0
  • SM331 6ES7 331-7KF02-0AB0
  • SM331 6ES7 331-7KB02-0AB0
  • SM331 6ES7 331-7PF00-0AB0
  • SM331 6ES7 331-7PF01-0AB0

To modules SM331 6ES7 331-1KF00-0AB0, SM331 6ES7 331-1KF01-0AB0 and SM331 6ES7 331-1KF02-0AB0 only encoders of the type 3-conductor method can be connected. This does not mean that you cannot use 4-conductor encoders. The fourth connector of the encoder remains unassigned with this method. The option of a 4-conductor connection, mentioned in the manual of 6ES7331-1KF0.-0AB0 in "Data for the Selection of an Encoder" refers to the method displayed in Fig. 1.


Fig. 1: 3-Conductor Connection

Please consider in this version, that both, the forth connector of the encoder and the I+ input of the SM 331 analog input block remain deactivated. The I+ input is exclusively needed in the measuring mode "CURRENT" .

To the analog input modules with order numbers 6ES7331-1KF0.-0AB0 and 6ES7331-1PF0.-0AB0 only 4-conductor encoders can be connected with the 4-conductor method (Fig. 2).


Fig. 2: 4-Conductor Connection

Note
In the case of 4-conductor and 3-conductor connections to the module 6ES7331-7PF0.-0AB0, the module provides a constant current via terminals IC+ and IC to compensate the drop in voltage on the measuring circuits. In order for the compensation to work properly, the resistance of the cables must not exceed 20 Ohm.
More information regarding these blocks can be found in the manual "SIMATIC Programmable Logic Controllers S7-300, Module Data" that is available under Entry-ID: 8859629. This manual also describes the 2- and 3-conductor connection of encoders.

Key Words
Wiring, Analog Value Recording, Hardware Configuration

How should you connect and wire measuring transducers and M connections taking the example of the SM331 (6ES7331-7KF02-0AB0 and 6ES7331-1KF01-0AB0)?Go to beginning
Part number:

Connecting and wiring measuring transducers and M connections to analog modules, compact CPUs and C7 compact devices

When wiring analog input channels you must observe a number of aspects, in particular the ground constellations. In the following we have taken difference measuring transducers (MT) and their wiring as examples:

  • Current measuring; mixture of active (4-wire MT) and passive (2-wire MT) measuring transducers.
  • Voltage measuring, thermocouples
  • Resistance thermometer, resistance
  • Isolated and non-isolated measuring transducers

We make a difference between modules with and without Mana (reference potential of the analog measuring circuit):

1. Sample connection with Mana: SM 331-7KF02


Fig. 01

2. Sample connection without Mana: SM 331-1KF01


Fig. 02

Notes:

  • With permissible common-mode voltage UCM = 1...8V, isolated measuring transducers must be connected with M or Mana (see sample connection above).
  • The measures apply for use in the CPU rack and for ET200M.
  • For unused or disconnected inputs see FAQ in Entry ID: 21557747
  • More information on these topics is available in the following manuals:
    "Programmable Logic Controllers S7-300 Module Data" Entry ID: 8859629
    "SIMATIC Programmable Logic Controllers S7-400 Module Data" Entry ID: 1117740
    CPU 31xC and CPU 31x, Technical Data Manual Entry ID: 12996906
    In the case of C7 devices, separate descriptions have been assigned for each device.

How do you connect a 2-wire measuring transducer to analog module 6ES7 331-1KF0.-0AB0, a compact CPU or a C7 device?Go to beginning
Part number:

Connecting 2-wire measuring transducers to analog module 6ES7 331-1KF0.-0AB0, a compact CPU or a C7 device
For analog modules that can be configured for 2-wire measuring transducers, please refer to the descriptions in the relevant manuals.

This description covers the following configurations:

  • Analog modules that can only be configured for 4-wire measuring transducers,
    like analog module 6ES7 331-1KF0.-0AB0.
  • Mixed operation of 2-wire and 4-wire measuring transducers on one channel group.
  • Compact CPUs or C7 devices.

Definition of the different transducers:

  • 4-wire measuring transducers have a separate power supply and two measuring cables that are connected to M+ and M- of the analog module. For this reason they are also called active measuring transducers.
  • 2-wire measuring transducers are also called passive measuring transducers, because they are normally supplied via the analog module.

To connect a 2-wire measuring transducer to an analog module (e.g. 6ES7 331-1KF0.-0AB0), a compact CPU or a C7 device, you need an external 24V power supply (Fig. 1).
This supply to the 2-wire measuring transducer must be short-circuit-proof. Provide a fuse to protect the power supply unit (Fig. 1). Please note that the analog input is not protected against destruction in case of a measuring transducer defect (short-circuit). For this case, make sure that you take the appropriate protection measures.


Fig. 1: Connecting 2-wire measuring transducers (block diagram)

M+: Positive measuring circuit
M-:  Negative measuring circuit
MANA: Reference potential of the analog measuring circuit
M :  Ground connection
L+:  DC 24V voltage supply connection

Notes:

  • The marking of the inputs depends on the module type; e.g. M+, M- .
    Please refer to the circuit diagrams for the individual modules.
  • The analog module must be configured in the HW Config as a 4-wire measuring transducer.
    This also applies when operating a mixture of 2-wire and 4-wire measuring transducers on one channel group.
  • Please refer to the description of the relevant module:
    S7-300 Programmable Logic Controller Module Data; Entry ID: 8859629
    CPU 31xC and CPU 31x, Technical Data Device Manual; Entry ID: 12996906
    In the case of C7 devices, separate descriptions have been assigned for each device.
How should you connect unused channels of analog input blocks?Go to beginning
Part number:

 

Description:
In order to operate analog channels without interference you must fulfill a number of conditions, in particular when inputs are not used. The following overview lists a number of appropriate measures:

Modules with MANA :

  • Connect all M- (measurement input negative) of the unused channels with MANA (reference potential of the analog measuring circuit).
  • If possible, connect MANA with the measuring transducer ground.
  • Short-circuit high-ohm inputs ( > 100kohms) or parameterize the current measurement in the range from 0 - 20/ + -20mA.
  • Jumper the unused compensation inputs COMP+/COMP-.
  • Unused sources of current may always remain open (connections IC+ / IC-).

Modules without MANA :

  • Modules with UCM <= 2.5V between the inputs:
    Connect all open M- with an M- of a used input.
    UCM is the common-mode voltage.
  • Modules with UCM > 2.5V between the inputs:
    Connect all open M- with the CPU ground or with the central ground of the facility.
  • Short-circuit high-ohm inputs ( > 100kohms) or parameterize the current measurement in the range from 0 - 20/ + -20mA.
  • Jumper the unused compensation inputs COMP+/COMP-.
  • Unused sources of current may always remain open (connections IC+ / IC-).

Notes:

  • All measures also apply for disabled channel groups.
  • Unused inputs of modules with an electrical isolation or UCM >= 60V between channels can remain open without ground connection in an environment free of interference.
  • No "open" cables should ever be connected to the inputs.
  • Measures (e.g. resistors, jumpers) for suppressing diagnostics messages at disabled inputs should be made via short connections (i.e. close to the module).
  • Unused reference points should be short-circuited.
  • Unused channels groups with the measuring range module slotted on a two-wire measuring transducer can be disabled without any additional wiring.

More information on these modules is available in the following manuals:

"Programmable Logic Controllers S7-300 Module Data" Entry ID: 8859629

"Programmable Logic Controllers S7-400 Module Data" Entry ID: 1117740

With the correct wiring, how can you avoid exceeding the common-mode voltage (Ucm) and subsequent measured value overflow or underflow in the analog input module 6ES7 331-1KF0.-0AB0?Go to beginning
Part number:

When operating the module, a maximum voltage of 2V is specified for the difference of potential Ucm (common-mode voltage) between the "M-" input terminals.
This data is available in the manual S7-300 Module Data, chapter 6.
Link to manual: Entry ID 8859629
The common-mode voltage can be slightly exceeded with open inputs and when potential-free measuring transducers are connected. Therefore you must take the following measures for isolated 4-wire measuring transducers and potential-free voltage sensors:

  • Connect M- of the inputs to each other and to the module ground.
  • Disable unused channels and likewise connect M- to the module ground.
  • In the case of disabled channels on the front connector, if long, open cables are connected, we recommend a jumper between M+ / S- and M-. This avoids sources of interference from these open cables.

Measurements for determining the error voltage between the "M-" terminals for determining the Ucm are not practical, because even high-ohm measuring devices cause equipotential bonding.


Fig. 01


Fig. 02

How should you deal with unused channels and wire break in the analog input module 6ES7 331-7PF01-0AB0?Go to beginning
Part number:

Description:

Wiring:
In order to operate analog channels without interference you must take a number of precautions, in particular when inputs are not used.
If channels or a channel group are not assigned in the SM 331-7PF01, you must short-circuit them.


Fig. 01

Wire break and diagnostics
If there is a wire break on channel (n) of a channel group, it might happen that this interferes with the signal of channel (n+1). If inversely there is a wire break on channel (n+1), this does not affect channel (n).
To be on the safe side here if there is a wire break on channel (n), you must generate a message for channel (n+1) because the measured value might be incorrect. For example, you can link the diagnostics bits of both channels with an OR.

How can you avoid exceeding the common-mode voltage (Ucm) with the SM 331-7KB02/-7KF02 modules and subsequent measured value overflow or underflow?Go to beginning
Part number:

 

Description:
The common-mode voltage can be slightly exceeded with open inputs and when potential-free measuring transducers are connected. Therefore you must take the following measures for isolated 4-wire measuring transducers, potential-free voltage sensors and isolated thermocouples:

  • M- of the inputs must be connected to the module ground
  • MANA must also be connected to ground
  • Connect unused COMP+ to ground

Note:
Measured value corruption can also occur with measuring transducers that are working properly if these measures are not taken.

Inputs of a channel group:

  • If you do not use both inputs of a channel group, slot the measuring range module on the "D" setting.
  • If you do not use one input in a channel group
    • refer to the specifications in the manual for the 4-20mA measuring range.
    • short-circuit the open input for the voltage/thermocouple measuring ranges (connect M+ with M-) and connect it to ground.

Please refer also to the manual:

"Programmable Logic Controllers S7-300 Module Data" Entry ID: 8859629

Why do you need a compensating box for connecting thermocouples to the analog modules SM331 (6ES7331-7KF02-0AB0 and 6ES7331-7KB02-0AB0) and how do you connect them?Go to beginning
Part number:

Compensating boxes are used for performing temperature measurements with thermocouples on analog modules. You require a compensating box whenever you transfer from the thermocouples to a copper wire via a terminal strip. The thermo-electromotive force occurring at this place (reference junction) is measured there with the compensating box and equalized.
The influence of fluctuations in temperature at the reference junction can be compensated for by an equalizing circuit. The compensating box (external compensation) is used as an equalizing circuit.

The compensating box contains a bridge circuit which is supplied by a mains-operated voltage source. A voltage of opposite polarity is added to the measured voltage and to the thermo-electromotive force, which occurs at the reference junction, thus compensating for the thermo-electromotive forces at the reference junction.
The compensating box must be located at the reference junction for the thermocouples and must have a voltage-free supply.

Compensating externally by connecting the compensating box to the COMP ports on the module can only be done for one particular type of thermocouple. All the channels which work with external compensation must use the same type. Compensating boxes must be used with a reference temperature of 0°C for the purposes of the compensation of the analog modules.

Note:
We recommend that you use a SIEMENS compensating box as the reference junction. The order data depends on the thermocouple you use and can be identified from the table below.


Fig. 1: Order data for the compensating box

The figure below shows how to connect a compensating box to the analog module.


Fig. 2: Connecting the compensating box

In these modules, the compensating box is connected to Pin 10 and Pin 11. If all the thermocouples in a module possess the same reference junction, the connection terminals for the compensating cables on the compensating box have to be short-circuited.

When parameterizing the modules in the HW Config, pay particular attention to the settings for the measuring type and measuring range.


Fig. 3: Setting the measuring type in the analog module SM 331 (6ES7331-7KF02-0AB0)

Follow an identical procedure for selecting the measuring type and measuring range on module SM331 6ES7331-7KB02-0AB0.

When you select the measuring type, you can choose between compensation and linearized compensation in the case of both internal and external compensation.
If you select linearized compensation, the corresponding value from the voltage temperature diagram is taken directly from the thermocouple characteristic, making it more precise than "normal" compensation. Normal compensation relates to the defined relationship between voltage and temperature.

Note:
More information about connecting thermocouples is available in the "SIMATIC Programmable Logic Controller S7-300 Module Data" manual in Entry ID: 8859629.

What should you watch out for with the supply of a 2-wire measuring transducer via the modules 6ES7331-7KF02-0AB0 and 6ES7331-7KB02-0AB0 with CPU switched off?Go to beginning
Part number:

If the transducer module is plugged in position "D", and the module on Pin 1 and Pin 20 is supplied with external voltage, the supply of a 2-wire measuring transducer continues. The fed current stays constant even with the CPU switched off.

More information about this is available in the manual "SIMATIC Programmable Logic Controllers S7-300 Module Data", Edition Sections 4.4 and 4.22.1. The manual is available in Entry ID 8859629.

How do you avoid the fluctuation in the analog inputs in the SM335 module (6ES7335-7HG01-0AB0)?Go to beginning
Part number:

The following wiring instructions apply for the analog input/output modules with the order numbers:

  • 6ES7335-7HG00-0AB0 

  • 6ES7335-7HG01-0AB0


Fig. 1: Wiring configuration for the analog inputs

Check whether you are using an ungrounded sensor installed on insulated mountings or whether your sensor is connected to ground.

Sensors installed on insulated mountings:

Connect the ground Mana (Pin 6) to the minus inputs of measuring channels M0- (Pin 10), M1- (Pin 12), M2- (Pin 14) and M3- (Pin 16) and to the central grounding point (CGP) by the shortest possible route (if possible, directly to the front connector).

Grounded sensors:
Ensure that there is good equipotential bonding on the sensor. Then isolate the connection from M- to Mana and to the central grounding point. Please place the shield on both sides.
As this configuration results in lots of noise during measurement, it would be better to use isolated sensors.

Keywords:
Analog modules, Wiring, Measuring connections

With the correct wiring, how can you avoid exceeding the common-mode voltage (Ucm) and subsequent measured value overflow or underflow in the module 6ES7 334-0CE01-0AA0?Go to beginning
Part number:

Description:
The "Overflow" message can also occur when the permissible difference of potential between the ground inputs of the analog inputs is exceeded. When operating the module 6ES7 334-0CE01-0AA0, a maximum voltage of 1V is specified for the difference of potential Ucm (common-mode voltage) between the "M-" input terminals.
This data is available in the manual S7-300 Module Data, chapter 6.
Link to manual: Entry ID 8859629

If there is no chassis ground connection between MANA and M, then the module switches off and the inputs are read in with 7FFFH ("Overflow"), outputs give the value 0. If the module is operated for a long period without chassis ground connection, this can lead to destruction of the module. Therefore, the analog ground MANA  must be connected to the ground of the CPU or the interface module (IM). The analog ground MANA (terminal 15 or 18) is on the module in the terminator area of the outputs.

Note:
Make these connections as short as possible and use a cable cross-section of at least 1 mm².

How do you connect a potentiometer to the analog module 6ES7 331-1KF0.-0AB0 (resistance measuring)?Go to beginning
Part number:

You can connect a potentiometer to the analog module 6ES7 331-1KF0.-0AB0 as follows.

  • Connect the potentiometer pick-off to terminal M+ of the channel concerned.
  • Connect a terminal point of the potentiometer to terminal M- of the input channel.
  • Then terminals S- and M- of the connected channel are connected to each other.


Fig. 1: Potentiometer connection for resistance measuring

Notes:

  • You can connect potentiometers of up to 6 KOhms.
  • If a variable input voltage is supposed to be formed with the potentiometer, the potentiometer pick-up must be connected to U+ and the M side of the potentiometer to M- of the module.

More information is available in the manual "SIMATIC S7-300 Programmable Controller Module Specifications" in Entry ID 8859629.

 Entry ID:22723668   Date:2013-10-09 
I regard this article....as helpfulas not helpful                                 






























mySupport
My Documentation Manager 
Newsletter 
CAx-Download-Manager 
Support Request
To this entry
Print
Create PDF 
Send to a friend
QuickLinks
Compatibility tool 
Help
Online Help
Guided Tour