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Pepperl+Fuchs Blog

Configuring the Intrinsic Safety Barrier KFD0-TR-Ex1

Posted by Aaron Severa on Tue, Aug 07, 2012

The KFD0-TR-Ex1 is an RTD converter

What you will want to do to fine tune this intrinsic safety barrier is as follows:

Look at these RTD Resistance Tables (PDF). The temperature value corresponds with the resistance values for the RTD.

KFD0-TR-Ex1 rotary switches function

1. Choose whether you want to adjust with linearization or without linearization. The resistance vs. temperature curve on an RTD is not completely linear – if you select without linearization the 4…20 mA signal will mimic this curve exactly. If you select with linearization, the 4…20 mA curve will be completely linear and may ‘stray’ off of the RTD curve slightly. This is done with the DIP Switches on the device. (shown below)

KFD0-TR-Ex1 dip switches function

2. Set the Span Rotary Dial to the required position. This is determined by looking at the upper temperature limit for your desired measurement range. If your temperature range is 0-200 °C, you will want to select the “2” position on the Span Switch (75…220 with linearization and 90…230 without linearization)

3. Set the Zero Rotary Dial to the required position. This is done by figuring out which zero point on the temperature scale they want to use. In this example, they want to go from 0-200 °C, so 0 °C is the zero point. Look down the column from which you just selected, in this case the “2” column to find the range 0 falls in. For both cases the Zero Switch will be in the “5” position.

4. Use the RTD Resistance vs. Temperature table from the link above to determine the corresponding resistance values for your two temperature points. 0 °C = 100 ohm. 200 °C = 175.86 ohms.

5. Input the low end (100 ohm) into the device using a fluke meter with an amp meter connected to the output side. Use the zero point potentiometer on the front until your amp meter reads 4 mA.

6. Input the high end (175.86 ohms). Use the span point potentiometer on the front until your amp meter reads 20 mA.

7. Repeat step 5. The reading on the amp meter may not be exactly 4 mA. Fine tune it until it is.

8. Repeat step 6. The reading on the amp meter may not be exactly 20 mA. Fine tune it until it is.

9. Keep repeating the process until every time you put your low resistance value in (100 ohms in this case), your amp meter reads 4 mA and every time you put in the high value (175.86 ohms), your amp meter reads 20 mA. It may take 2 or 3 cycles for this to happen.

Topics: Troubleshooting, Intrinsic Safety Barriers

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