The Modular PLC Family: SIMATIC S7-300 Version 0..9 Introducing S7-300 RTD & Thermocouple Modules 8 Channel Resistance Temperature Device Module 8 Channel.

The Modular PLC Family: SIMATIC S7-300 Version 0..9

Introducing S7-300 RTD & Thermocouple Modules

8 ChannelResistance Temperature Device

Module

8 ChannelThermocouple

Module

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Thermocouple Module

The thermocouple module provides a convenient, isolated, interface for the S7-300 family to 10 thermocouple types;

B, N, E, R, S, J, L, T, K, U

Thermocouple type, open wire check, temperature scale, cold junction compensation and burnout direction are all user selectable via software using the Hardware Configuration setup in STEP7.


RTD Module

The RTD module provides a convenient, interface for the S7-300 family to ten different RTD types,

Pt 100, Pt 200, Pt 500, Pt 1000, Ni 100, Ni 120, Ni 200, Ni 500, Ni 1000, Cu 10

Different Alpha characteristics are supported for the different types of RTD to provide increased accuracy of the temperature measurement.

Also three resistive input range are supported for slide wire inputs or other types of linear resistance signals.

RTD type, open wire check, temperature scale, and are all user selectable via software using the Hardware Configuration setup in STEP7.


S7-300 RTD &Thermocouple Modules - Key Features

MLFB . . . . . . . . . . . . . . . . . . . . . . . . . . Number of Channels . . . . . . . . . . . . . Input Sensor Types . . . . . . . . . . . . . . .

Broken Sensor Detection . . . . . . . . . . Accuracy over 0 to 60 °C operating .

Range Repeatability (full scale) . . . . . . . . . . . Resolution (temperature) . . . . . . . . . . Resolution (voltage or Resistance) . . Linearity . . . . . . . . . . . . . . . . . . . . . . . . . Data Word Format . . . . . . . . . . . . . . . . Module update time . . . . . . . . . . . . . . .

Isolation (Field-to-Logic) . . . . . . . . . . Withstand (Channel-to-Channel) . . . Common Mode Rejection . . . . . . . . . . Suppression of Interferance . . . . . . . External Power Source . . . . . . . . . . . Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . Weight . . . . . . . . . . . . . . . . . . . . . . . . .

Thermocouple 6ES7 331 7PF10 0AB0 8 B,L,S,T,R,U,E,N,K,J

Yes ± 1.0 Deg. C

± 0.01 % of input range 0.1 or 0.01 °C / °F 23 bits plus sign ± 0.02 % of input range Degrees C or F 10 mS 4 Channel mode 46 mS 8 Channel mode 500 VAC 120 VAC >120 db @ 120 VAC 50/60/400 Hz 24 VDC 40 x 125 x 120mm 272 grams

RTD 6ES7 331 7PF00 0AB0 8 2,3 and 4 Wire Types ,

PT100~10,000,

Cu10, Ni 100 ~ 1000 & Resistance Yes ± 1.0 Deg. C

± 0.01 % of input range 0.1 or 0.01 °C / °F 23 bits plus sign ± 0.02 % of input range Degrees C or F 10 mS - 4 Channel mode 40 mS - 8 Channel mode 500 VAC 120 Vac >120 db @ 120 VAC 50/60/400 Hz 24 VDC 40 x 125 x 120mm 272 grams


Introduction to Temperature Measurement

Background Information

Thermocouples are typically used in applications that require a response time between 2 to 5 seconds

depending on the installation, operate over a wide range temperatures, and needs a cost effective /

economical solution. The non-linear characteristic of a thermocouple is the primary disadvantage.

RTDs are typically used in applications that require a fast response time of less than 1 second. The RTD’s

accuracy and linearity are the primary advantages for this sensor. The limited operating range and a single

current source which effects isolation, are the primary disadvantages.

Characteristics Thermocouple RTD

Response to change in temperature Slow to Medium

Depending on junction type

Fast

Temperature range supported -270 to 1802 Deg C

Depending on type

- 200 to 850 Deg C

Accuracy shift Characteristics Non-Linear Linear

Will EMI effect the accuracy? Yes with grounded T/C

Reduce w/ ungrounded T/C

Minimal

Termination compensation required Yes No

Overall Operating Temperature Range High Low

Isolation between points requested Yes Yes


Applications Requiring Temperature Measurement

Applications requiring temperature measurement cut across all applications, industries and markets. Below is a partial listing of applications requiring temperature measurement.

Batch process Electroplating Environmental chambers Food service equipment Furnaces Control General process control Heat or cool control Heat treating HVAC equipment Medical and dental equipment Oven equipment Packaging equipment Percent power, open loop control Textile processing equipment Plastics processing equipment Processes needing temperature data logging Pulp and paper equipment Semiconductor manufacturing


Background Information

on

RTD and T/C's


S7-200 RTD Module - Background Information

RTD - abbreviation for Resistance Temperature Detector. It is a sensor which operates on the principle that the resistance increases with an increase in temperature at a specific rate.

Commonly manufactured using a platinum resistance element. More accurate and more linear than most thermocouples.

RTD sensors are designed to take the temperature of liquids, semisolid materials and for insertion into holes or cavities.

RTD sensors are available with American and European configuration curves.


7 Key RTD Specifications

RTD SPECIFICATIONS

#1 Sensor Material - Several metals are quite common for use in RTD's.

Platinum is by far the most popular due to its near linearity with temperature,

wide temperature operating range, and superior long-term stability. Other

materials are nickel, copper, balco (an iron-nickel alloy), tungsten, and iridium.

#2 Temperature Coefficient - The temperature coefficient (TC), or alpha of an

RTD is a physical and electrical property of the metal alloy and the method by

which the element was fabricated. The alpha describes the average resistance

change per unit temperature from the ice point to the boiling point of water.

#3 Nominal Resistance - Nominal resistance is the resistance value at a given

temperature. Most standards, including IEC-751, use 0°C as their reference point

because it is easy to reproduce. The International Electrotechnical Commission

(IEC) specifies the standard based on 100.00 Ohms at 0°C, but other nominal

resistance's are quite common.



RTD SPECIFICATIONS

#4 Wiring Configuration - An RTD is inherently a 2-wire device,

but lead wire resistance can drastically reduce the accuracy of the

measurement by adding additional, uncompensated resistance

into your system.

Most applications therefore add a third wire to help the circuit

compensate for lead wire resistance, and thus provide a truer

indication of the measured temperature.

Four-wire RTD's provide slightly better compensation, but are

generally found only in laboratory equipment and other areas

where high accuracy is required.

#5 Temperature Range - The ASTM states that platinum RTD's

can measure temperatures from 200°C to 650°C and the IEC

specifies -200°C to 850°C.



RTD SPECIFICATIONS

#6 Accuracy - RTD's are generally known for their high degree of accuracy.

• Key to understand is the difference between accuracy, precision, and repeatability.

• Accuracy: In temperature measurement, accuracy is commonly defined as how closely the sensor indicates the true temperature being measured, or in a more practical sense, how closely the resistance of the RTD matches the tabulated or calculated resistance of that type RTD at that given temperature.

• Precision: Precision is not concerned with how well the RTD's resistance matches the resistance from a look-up table, but rather with how well it matches the resistance of other RTD's subjected to that temperature. This is important when interchangeability is a concern, as well as in the measurement of temperature gradients. Precision can best be described as the sensor's ability to reproduce its previous readings at a given temperature.

• Repeatability: An RTD's repeatability is very application-dependent. A RTD sensor, when applied properly in an application, can have both good accuracy and repeatability. But just a high-accuracy RTD installed in a field application does not ensure that you will be getting a highly accurate signal back at the PLC. The complete installation must be well engineered. The best solution for applications of this type is to have both the RTD and the transmitter, or display, or whatever, calibrated as a unit by a certified calibration laboratory.



RTD SPECIFICATIONS

#7 Dimensions and Size - The physical dimensions and sizes of RTD probes will vary depending on the application needs. Generally, a RTD resistance element is installed in a metal sheathed assembly.


Key Thermocouple Specifications

Thermocouple - a temperature sensor based on the principle that a voltage is produced

when two dissimilar metals are joined together at a junction. The junction produces a

voltage in proportion to the difference in temperature between the measuring junction and

the reference junction.

The selection of the optimum thermocouple type (metals used in their construction) is based

on application temperature, atmosphere, required length of service, accuracy and cost.

Different thermocouple types have very different voltage output curves.

Cold Junction Compensation measures the ambient temperature at the connection of the

thermocouple wire to the measuring device (ie: S7-300 T/C module). This allows for

accurate computation of the temperature at the hot junction by the measuring device.


Thermocouples and Cold Junction Compensation

The open-end EMF generated (V1) is a function of not only the closed-end temperature T1 (i.e., the temperature at the point of measurement) but also the temperature at the open end (T2) where the thermocouple wires are attached to the S7-300 thermocouple module .

Only by holding T2 at a standard temperature can the measured EMF (V1) by the S7-300 thermocouple module be considered a direct function of the change in T1.

The industrially accepted standard for T2 is 0°C; therefore, the S7-300 thermocouple module makes the assumption that T2 starts at this level.

In the S7-300 thermocouple module , the difference between the actual temperature at T2 and 0°C is corrected for electronically, within the module. This EMF adjustment is referred to as the cold-junction, or CJ, correction. The 300 T/C module provides two options for measuring this temperature.

The 300 T/C module provides internal temperature measurement inside the module. This method is used when thermocouple wire or T/C extension wire is used from the sensor to the module.

If copper wire is used from a junction box to the module then the 300 T/C module provide an input for a two-RTD sensor to measure the temperature at the point where the wiring changes from T/ C wiring to copper wiring. This type of installation will have a reduced accuracy unless all eight channels are terminated in the same enclosure.

T 1V 1T 2

The installed S7-300 control panel must be at a 'stable' temperature to gain the maximum accuracy the cold junction compensation of the Thermocouple

Module is designed to deliver.


Examples of Thermocouple Wire Color Codes

Thermocouple wiring is color coded by thermocouple types.

Different countries and standards may utilize different color coding.

Jacket coloring is sometimes a colored stripe instead of a solid color.

French NFE German DINUnited StatesASTM

British BS1843 1952

COPPER Cu

CHROMEGA NICKEL- CHROMIUM Ni-Cr

‡IRON Fe (magnetic)

R = PLATINUM 13% RHODIUM Pt-13% RhS = PLATINUM 10% RHODIUM Pt-10% Rh


S7-300 RTD and T/C Specifications


The S7- 331-7PF RTD and T/C I/O Modules – … Super Performance at a Great Price.


The S7- 331-7PF RTD and T/C I/O Modules – … Super Performance at a Great Price.

The Modular PLC Family: SIMATIC S7-300 Version 0..9 Introducing S7-300 RTD & Thermocouple Modules 8 Channel Resistance Temperature Device Module 8 Channel.

Documents

simatic s7

modular plc family

temperature scale

resolution temperature

temperature of liquids

temperature coef

rtd sensors

different rtd types