Belajar memakai Module Thermocouple (T/C) 1756-IT6I, Controllogix


Sekedar sharing dan catatan pribadi ..

Bbrp hari kemarin ada pekerjaan troubleshooting Module Thermocouple (T/C) 1756-IT6I.
Module yang terpasang ada indikasi channel fault dan akhirnya diganti.
Nah pas diganti ternyata bacaan semua T/C Channel ada penurunan semua.
Ada dugaan kemungkinan karena module sebelum dan sesudah dipasang beda revisi. Atau mungkin saja perlu Module Reset dan kemungkinan lainnya.
Berhubung belum pernah utak-atik module jenis ini sebelumnya dan supaya tidak mengganggu unit yang sedang running maka kami coba di shop dulu.
Di shop kami punya simulator Controllogix dan spare module IT6I.

User Manual yang kami pakai adalah Publication 1756-UM009C-EN-P – December 2010 : ControlLogix Analog I/O Modules
Chapter 6. Temperature-measuring Analog Modules (1756-IR6I, 1756-IT6I, and 1756-IT6I2)

Sekilas cuplikannya beserta beberapa komentar.
(bhs inggrisnya terjemahin sendiri aja yah)

Introduction
The 1756-IR6I uses ohms for temperature conversions and the two thermocouple modules (1756-IT6I, 1756-IT6I2) convert millivolts.

Underrange/Overrange Detection
This feature detects when a temperature-measuring input module is operating beyond limits set by the input range. For example, if you are using the 1756-IR6I module in the 2…1000 Ω input range and the module resistance

increases to 1050 Ω, the overrange detection detects this condition.

The table lists the input ranges of non-isolated input modules and the lowest/highest signal available in each range before the module detects an underrange/overrange condition.

Wire Off Detection
The ControlLogix temperature-measuring modules alert you when a wire has been disconnected from one of their channels.

When a wire off condition occurs, two events occur:

• Input data for that channel changes to a specific scaled value.
• A fault bit is set in the owner-controller that may indicate the presence of a wire off condition.

Catatan:
wire off ini kita pakai untuk mengetahui kabel putus.

Sensor Type
Three analog modules, the RTD (1756-IR6I) and Thermocouple (1756-IT6I and 1756-IT6I2), lets you configure a sensor type for each channel that linearizes the analog signal into a temperature value. The RTD module linearizes ohms into temperature and the Thermocouple modules linearize millivolts into temperature.

Catatan:
Kami pakai T/C Type K.

Berikut penjelasan di Wikipedia tentang T/C Type K

Referensi: http://en.wikipedia.org/wiki/Thermocouple
Type K (chromel {90% nickel and 10% chromium}–alumel {95% nickel, 2% manganese, 2% aluminium and 1% silicon}) is the most common general purpose thermocouple with a sensitivity of approximately 41 µV/°C (chromel positive relative to alumel when the junction temperature is higher than the reference temperature).[9] It is inexpensive, and a wide variety of probes are available in its −200 °C to +1350 °C / -330 °F to +2460 °F range. Type K was specified at a time when metallurgy was less advanced than it is today, and consequently characteristics may vary considerably between samples. One of the constituent metals, nickel, is magnetic; a characteristic of thermocouples made with magnetic material is that they undergo a deviation in output when the material reaches its Curie point; this occurs for type K thermocouples at around 350 °C . Wire color standard is yellow (+) and red (-).

When you select any of the sensor or thermocouple types (listed in the table) during configuration, RSLogix 5000 software uses the default values in the scaling box.

The table displays the temperature range for each 1756-IR6I sensor type.

The table displays the temperature range for each 1756-IT6I and 1756-IT6I2 sensor type.

Temperature Units
The 1756-IR6I, 1756-IT6I and 1756-IT6I2 modules provide the choice of working in Celsius or Fahrenheit. This choice affects all channels per module.

Differences Between the 1756-IT6I and 1756-IT6I2 Modules
The 1756-IT6I and 1756-IT6I2 modules support grounded and ungrounded thermocouples. However, in addition to offering access to two more thermocouple types (D and TXK/XK [L]), the 1756-IT6I2 module offers the following:
• A greater cold-junction compensation accuracy
• Improved module accuracy

While the 1756-IT6I module can report cold junction temperature differences between channels as high as 3 °C from the actual temperature, the 1756-IT6I2 module, because it has two cold-junction sensors (CJS), reduces the potential cold-junction error from actual temperature to 0.3 °C.

It’s important that you check that the CJS is fitted locally or remotely, and enabled accordingly in the module channel configuration. If the CJS is not fitted or if the sensor wiring leads are incorrect (for example, swapped over at the thermocouple cards input), there’s a possibility of a negative or positive temperature fluctuation when the thermocouple sensor is warmed.

The table lists the cold junction error from actual temperature, depending on the type of cold junction compensation that is used.

Cold Junction Compensation
When using the thermocouple (1756-IT6I and 1756-IT6I2) modules, you mustaccount for additional voltage that may alter the input signal. A small voltage generates at the junction of the thermocouple field wires and the screw

terminations of an RTB or IFM. This thermoelectric effect alters the input signal.

To accurately compensate the input signal from your module, you must use a cold junction sensor (CJS) to account for the increased voltage. Because there are differences if you choose to connect sensors via an RTB or IFM, you must configure the module (via RSLogix 5000 software) to work with the type of CJS used in your application.

Connecting a Cold Junction Sensor Via a Removable Terminal Block

When you connect a CJS to your thermocouple module via an RTB, the following occurs, depending on module type:
• The 1756-IT6I module uses one CJS in the middle of the module and estimates temperature deviation elsewhere on the connector.
• The 1756-IT6I2 module uses two CJSs at the top and bottom of the module and calculates temperature at each channel’s input terminals; this usage of multiple sensors results in increased accuracy.

If you connect a CJS via an RTB, configure the module as shown on the Module Properties Configuration tab.

Catatan:
Setting ditempat kami sebelumnya memang tidak di check (unchecked).
Tapi waktu simulasi kemarin sempat kami check Remote CJ Compensation sempat nilai bacaannya lebih bagus.
Tapi pas di unchecked sama saja nilainya. Jadi agak bingung bedanya apa. Paling merefer ke info di atas saja.

Connecting a Cold Junction Sensor to the 1756-IT6I Module
You must connect the CJS to the 1756-IT6I module at terminals 10 and 14. To ease installation, wire terminal #12 (RTN-3) before connecting the cold junction sensor.

Catatan:
CJS ini disuplai bareng module.
Saat simulasi tanpa CJS dipasang memang ada bacaan temp. selisih yang cukup significant.

Cold Junction Disable Option
The Cold Junction Disable box on the Module Properties Configuration tab disables cold junction compensation on all module channels.

Typically, this option is used only in systems that have no thermoelectric effect, such as test equipment in a controlled lab.

In most applications, we recommend that you do not use the cold junction disable option.

Cold Junction Offset Option
The Cold Junction Offset box on the Module Properties Configuration Tab lets you make module-wide adjustments to cold junction compensation values.

If you know that your cold junction compensation values are consistently inaccurate by some level, for example, 1.2 °C (34.16 °F), you can type the value into the box to account for this inaccuracy.

Wire the Modules
The illustrations show wiring examples for the 1756-IR6I, 1756-IT6I, and 1756-IT6I2 modules.

1756-IR6I 3-Wire RTD wiring example

1756-IR6I 4-Wire RTD wiring example

1756-IT6I Wiring Example

Catatan:
Simulasi menggunakan wiring di atas.

1756-IT6I2 Wiring Example

Dengan info di atas maka berikut ilustrasinya Simulasi signal T/C ke Module 1756-IT6I dengan menggunakan Fluke Documenting Process Calibrator.

Konfigurasi di RSLogix5000 nya.

Monitor datanya… di Controller tag

Catatan:
gambar diatas hanya ilustrasi saja. Nilai-nilainya tidak pas antara gambar satu dan lainnya karena bukan dicapture saat simulasi..
Setelah dicoba-coba ada beberapa pertanyaan yang mengganjal seperti:
• apa bedanya ketika di check Remote CJ Compensation bacaan jadi akurat pas di uncheck tetap akurat.
• Sebelum CJS dipasang, selisih bacaan temp. sekitar 40 degF. Tapi yang dilapangan selisihnya bisa 100 degF
• Ketika module minor revision diubah bacaan temperaturenya tidak ada perubahan. (saat kasus penggantian, memang module yang pasang lebih tinggi minor revisinya. Configurasi di module ternyata tidak menyesuaikan dengan minor revisi module yang terpasang)

Rencana nanti akan di coba di lapangan pas waktu unit service.

Controllogix dengan Module T/C

Controllogix dengan Module T/C

 

 

 

 

 

 

 

 

 

 

Mungkin kalau update info bisa kami tambahkan disini.
Atau jika ada yang punya pengalaman silahkan disharing.

Semoga bermanfaat…

Artikel PLC / HMI lainnya:
https://juare97.wordpress.com/plc-hmi/

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