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931-AT002

931-AT002
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Infrastructure for the Architecture Creating an electrical infrastructure that maximizes the reliability of your critical control circuits Signal Conditioners - Thermocouple Application Solutions for Long Wire Runs Application Care needs to be taken when using thermocouples. The entire length of the thermocouple is the sensor, so the shortest possible length is a key consideration. Additionally, the output signal generated by a thermocouple is a low level voltage signal (micro volts) and excessive lengths of thermocouple wire act as an antenna to any stray EMI. So, a 100 foot distance in an industrial environment would eliminate the consideration of a point to point thermocouple wiring scheme. An additional factor is that the existing ControLogix analog card does not interface directly with the thermocouple, so either an additional thermocouple Card needs to be used or the thermocouple signal needs to be converted to a standard current (4-20mA) or voltage (0...10VDC) signal. Initial Situation Type J thermocouple positioned 100 ft from the ControlLogix cabinet. Existing analog input card with an open channel that requires a 4...20mA input signal. µV voltage 100’ Thermocouple wire • Direct connection • No additional components • Larger investment for functionality that may not be required/utilized • Bigger, fixed PLC footprint - due to required and costly thermocouple module • Uses 100’ of costly thermocouple wire • Susceptible to EMI and ground loops • Inaccu

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Component Solution - Signal Conditioner Type J thermocouple positioned 100 ft from the ControlLogix cabinet. Bulletin 1492 J thermocouple terminal block and 931 Signal conditioner convert signal and allow for 100’ of copper wire - which is more durable and improves the signal quality. Bulletin 1492 J Thermocouple Terminal Block 4...20 mA 100’ copper wire Bulletin 931 Signal Conditioner Component Solution Bill of Materials Product Terminal Block Signal Conditioner Option1 Signal Conditioner Option2 Signal Conditioner Option 3 • Requires more components • Requires auxiliary power source Cost...

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Summary The recommended configuration is as follows: Bulletin 931 Signal Conditioner Bulletin 1492 Thermocouple Terminal Block ControlLogix Analog Input Module A short length of thermocouple wire can be run from the temperature monitoring point and terminated directly to the 1492 Thermocouple Terminal Block. The 1492 Thermocouple Terminal Block utilizes matching metal contacts, thus eliminating any errors in measurement due to dissimilar metal effects. This 1492 Thermocouple Terminal Block also allows for an efficient modular assembly method that protects the fragile thermocouple wire....

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