Delta v Course 7009-15

FISHER-ROSEMOUNT SYSTEMS RTD / Thermocouple / I/O InterfaceCourse 7009 -- Rev 3 - 4/15/01

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TM

RTD & Thermocouple I/O Interface


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Upon completion of this module you will be able to:

Define RTD/Ohm I/O Interface

Define RTD wiring connections

Configure the RTD Card

Configure RTD channel properties

Configure a temperature module using a RTD sensor

Objectives


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RTD Terminal Block Wiring

2-Wire 3-Wire 4-Wire


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The DeltaV RTD/Ohm I/O Interface supports up to 8 RTD or Ohm inputs.

Resistance Temperature Devices (RTDs) change resistance with respect to temperature. A commonly used RTD is a 100 Ohm platinum sensor with a range from -328 °F to 1562 °F. The DeltaV RTD card senses the resistance and passes the value as a percentage to the Controller. An AI block in a control module scales the percentage to a temperature value in degrees Fahrenheit, Celsius or Kelvin.

In an ideal world a 2-wire RTD would provide a very accurate reading. However, the lead wire resistance will offset the actual temperature. Thus a 3-wire provides a more accurate reading because the RTD card can sense the resistance of one lead wire and negate the lead wire resistance.

However, in a 3-wire application we can only estimate the resistance of the other lead wire. Thus a 4-wire is more accurate as it will send a current out (sensor excitation) and determine the actual resistance of both leads and negate all lead resistance.

The illustration above shows the wiring connections for 2,3 and 4 wire RTDs connected to channel 1.

RTD Terminal Block Wiring


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RTD WorkshopThis workshop requires you to perform the following tasks:

Task 1. Install the RTD card and terminal block.

Task 2. Wire a 3-Wire RTD.

Task 3. Configure the RTD card.

Task 4. Configure the RTD channel.

Task 5. Configure a control module to show room temperature.


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Workshop - Install Card & RTDStep 1. Install your RTD card and terminal block in slot 6.

Step 2. Connect the 3-Wire 100 Ohm Platinum RTD to channel 1 as shown below.

Black

Red

White


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Configure the RTD Card

Configure a new RTD card in slot 6 by selecting the I/O category and selecting a new RTD Input Card 8 Ch as shown above.

Alternately, you may autosense the card if it is already plugged into the carrier.


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Configure RTD Channel Properties

Select the Properties for channel 1. Define the following key items:

Step 1. Enable the channel.

Step 2. Set the Channel Type to Pt 100 RTD Input Channel.

Step 3. Name the channel with the Device Tag(DST) RTD1.


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NUM_WIRES Parameter

Set the NUM_WIRES parameter to 3 as shown above.

The 100 Ohm platinum RTD in our workshop is a 3 wire sensor. Therefore, it is necessary to set the NUM_WIRES parameter to 3.


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Module RMTEMP-101 Configuration

Create a new module as shown above from the Library using the Monitoring/Analog module template. The following pages take you through the AI1 block and modify the necessary parameters to properly read the temperature from the RTD sensor.


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Step 1. Set IO_IN Device Tag to RTD1.

Step 2. Set IO_IN Parameter to FIELD_VAL to read the temperature in degrees. If IO_IN is set to FIELD_VAL_PCT, the output will only show the value in percent which would rarely be used for a temperature.

IO_IN Parameter


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Set L_Type to Direct because the transducer, or RTD, has units that directly relate to the OUT value displayed to the operator, -328 to 1562 °F.

L_TYPE Parameter


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Set the OUT_SCALE Engineering Units to °C or °F depending on your preference.

It isn’t necessary to enter 0% or 100% scale because the system will automatically scale the output based on the sensor selected on the channel properties. See the result on the next page.

OUT_SCALE Parameter


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Auto Scaling

Step 1. Complete the configuration as follows:a. Assign to your controllerb. Save the module as RMTEMP-101c. Download the moduled. Don’t forget to download the

RTD card

Step 2. View the module in the On-line view. As shown above left, while in edit mode the 0% and 100% scale is not defined. Once downloaded the On-Line view above right shows both OUT_SCALE and XD_SCALE are automatically set.


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Alternative ConfigurationThe AI block was configured using L_TYPE as Direct. This only requires selecting the units under OUT_SCALE. If L_TYPE were set to Indirect the configuration person would have additional data entry as shown by the .

L_TYPE = Direct L_TYPE = Indirect

XD_SCALE XD_SCALE

100% = * 100% = *

0% = * 0% = *

Units = * Units = °F

OUT_SCALE OUT_SCALE

100% = * 100% = 1562

0% = * 0% = -328

Units = °F Units = °F

* Automatically filled in based on channel configuration.


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SummaryYou should now be able to:

Define the functionality of the RTD card

Configure an RTD card

Configure RTD channels

Configure a control module to read process temperatures using a RTD


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Thermocouple/mV I/O InterfaceTM


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This module introduces you to the Thermocouple/mV I/O Interface. Upon completion of this module you will be able to:

Define Thermocouple/mV I/O Interface

Define Thermocouple wiring connections

Configure the Thermocouple Card

Configure Thermocouple channel properties

Configure a temperature module using a Thermocouple

Objectives


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Thermocouple Terminal Block

(+) Positive

(-) Negative

Blue (+)

Red (-)

Thermocouple sensorat the process.

InherentThermocouple(Cold Junction)


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The DeltaV Thermocouple/mV card supports up to 8 Thermocouples or mV inputs.

Thermocouples consist of two dissimilar metals twisted together which generate a millivolt signal with respect to temperature.

The Thermocouple terminal block contains sensors for cold junction compensation. An inherent Thermocouple is created at the screw terminals where the wires are connected. The screw terminals are also dissimilar metals that create a millivolt signal(cold junction).

Cold junction compensation counters the millivolt signal generated at the terminal block by sensing temperature at the terminal block with an internal sensor in the terminal block.

Note: When the Thermocouple card is plugged into a Thermocouple terminal block the card functions as a Thermocouple card. When the Thermocouple card is plugged into a standard I/O terminal block it functions as a mV card.

Thermocouple Terminal Block


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Thermocouple Workshop

This workshop requires you to perform the following tasks:

Step 1. Install the Thermocouple card and terminal block.

Step 2. Wire the Thermocouple.

Step 3. Configure the Thermocouple card.

Step 4. Configure the Thermocouple channel.

Step 5. Configure a control module to show room temperature.


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Blue (+)

Red (-)

Step 1. Install your Thermocouple card andterminal block in slot 7.

Step 2. Connect the type T Thermocouple to channel 1 as shown below.

Note: If you do not have a Thermocouple available you can simply short screw terminals 1and 2. Proceed with the configuration on the following pages as if you had a thermocouple and you will be reading the temperature at the terminal block sensed by the cold junction compensation.

Install Card & Thermocouple


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Configure the Thermocouple Card

Configure a new Thermocouple card in slot 7 by selecting the I/O category and selecting a new Thermocouple Input Card, 8 Ch as shown above.

Alternately, you may autosense the card if it is already plugged into the carrier.


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Configure the Thermocouple Channel Properties

Select the Properties for channel 1. Define the following key items:

Step 1. Enable the channel.

Step 2. Select the appropriate Channel Type. The example above assumes aType T Copper/Constantan (Copper-Nickel) Thermocouple.

Step 3. Name the channel with the Device Tag (DST) “TC1”.


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CJT_CHAN Parameter

Verify CJT_CHAN is set to Local Compensation, which is the default. This will provide cold junction compensation for the entire card by using the internal sensor in the terminal block. The configuration person could change this to any of the 8 channels. Then the card would use the value on that channel as the temperature for cold junction compensation.


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Module RMTEMP-201 Configuration

Create a new module as shown above from the Library using the Monitoring/Analog module template. The following pages take you through the AI1 block and modify the necessary parameters to properly read the temperature from the Thermocouple.


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Step 1. Set IO_IN Device Tag to “TC1 ”.

Step 2. Set IO_IN Parameter to FIELD_VAL to read the temperature in degrees. If IO_IN is set to FIELD_VAL_PCT, the output will only show the value in percent which would rarely be used for a temperature.

IO_IN Parameter


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Set L_Type to Direct. The reason for this is that the transducer or Thermocouple in this case has units that directly relate to the OUT value that will be displayed to the operator, -454 to 752 °F.

L_TYPE Parameter


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Set the OUT_SCALE Engineering Units to °C or °F (your preference).

It isn’t necessary to enter 0% or 100% scale as the system will automatically scale the output based on the sensor selected on the channel properties, see the result on the next page.

OUT_SCALE Parameter


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Auto Scaling

Step 1. Complete the configuration as follows:a. Assign to your controllerb. Save the module as

RMTEMP-201c. Download the moduled. Don’t forget to download the

Thermocouple card

Step 2. View the module in the On-line view. As shown above left, while in edit mode the 0% and 100% scale is not defined. Once downloaded the On-Line view above right shows both OUT_SCALE and XD_SCALE are automatically set.


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Alternative Configuration

Our AI block was configured using L_TYPE as Direct. This only requires selecting the units under OUT_SCALE. If L_TYPE were set to Indirect the configuration person would have additional data entry as shown by the .

L_TYPE = Direct L_TYPE = IndirectXD_SCALE XD_SCALE

100% = * 100% = *0% = * 0% = *

Units = * Units = °F

OUT_SCALE OUT_SCALE100% = * 100% = 752

0% = * 0% = -454

Units = °F Units = °F

* Automatically filled in based on channel configuration.


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SummaryYou should now be able to:

Define the functionality of the Thermocouple card

Configure a Thermocouple card

Configure Thermocouple channels

Configure a control module to read process temperatures using a Thermocouple


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Delta v Course 7009-15

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