Tech Tip: Shunt Resistors |
Remember to disconnect power when servicing 4-20 mA circuits or you may damage the "Shunt" Resister in the IO module. Shunt resisters are used to change the 4-20 mA current in the current loop to a voltage that the IO Module can measure. They are usually between 100 and 250 Ohms and are usually replaceable as they also act as a fuse. Shorting the + and - wires together in the field allows unlimited current to flow until the Shunt Resister burns out. When disconnecting field wiring either turn off power or remove 1 wire at a time and use electrical tape to protect the bare wires. |
Did You Know ? |
 STI's CMCP575 Speed Transmitter has a frequency response of 0.031 Hz to 38,000 Hz with 0.1% Accuracy. That's a low end of 1.86 RPM with a once per turn pulse. Setup is easy by simply providing a desired full scale input and pressing a single button. For more information see our online CMCP575 Data Sheet and CMCP575 Manual.
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Frank Howard
President
Office: 281.334.0766 x232
Cell: 281.844.2569
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