Description
Learn the proper way to connect 2, 3, or 4-wire RTD probes to your data logger or measuring instrument by following manufacturer wiring diagrams and color codes. We’ll guide you through terminal block connections, avoiding shorts, and securing wires correctly to ensure accurate measurements. For support on wiring up RTD's to your devices, reach out to IOThrifty.com.
Transcript
Today we'll be covering how to connect or wire your RTD probe for use with a datalogger or other measuring instrument. Before we begin, please refer to the manufacturer's wiring diagram as the color coding may vary between suppliers. The probe's documentation should indicate the use of each wire if the wire colors do not match our typical black and red examples.
Our first example is a 4 wire RTD probe, which is in most cases the best choice when available. According to Madgetech's wiring diagram, a black wire should be connected to Terminal 1, and in Terminal 2, another black wire. A red wire should be connected to Terminal 3, And then the other red wire should be connected to Terminal 4.
Our second example is a 2 wire probe. In this example, a black wire should be connected to Terminal 2, and a red wire should be connected to Terminal 3. A small wire should be used to short Terminal 1 to Terminal 2, so they are electrically connected. And in the same way, a small wire should be used to short Terminal 4 to Terminal 3, so they are electrically connected.
Take care that the shorting wires do not allow a short between the positive and negative terminals. Terminals 1 and 2 should be electrically isolated from terminals 3 and 4. With a 3 wire RTD, the color with 2 wires should be wired according to the 4 wire RTD instructions. For example, if we have two black cables, one black wire should be connected to terminal 1 and another to terminal 2.
But the color with only a single wire should be wired and shorted according to the two wire RTD instructions. Mixing up the order of the wires will result in erroneous readings. When attaching the wires to the terminal block, it is important to ensure a secure connection between the clamp and the block and the bare wire.
If there is insulation between the wire and the clamp, it will not work properly. The insulation should be stripped to expose enough wire for a good electrical connection. That being said, exposing too much bare wire should be avoided, as this could pose the risk of bare wires touching each other outside of the terminal block, which could create a short and lead to incorrect readings.
Use the screws in the terminal block to fasten the wires in each port securely. While also being careful not to over tighten them.