Note : These errors will result only if the paralleled wires carry current.
![motor winding rtd motor winding rtd](https://www.termoaparatura.com.pl/images_mce/czujnik_uzwojen.png)
By paralleling two of the four wires in the 4-wire cable, you will create unequal resistances in the current path, thus leading to measurement errors at the transmitter (Note). Jumpers placed at the transmitter terminals defeat the purpose of the transmitter’s 3-wire or 4-wire capabilities, downgrading its performance to that of a 2-wire system.Ī similar problem occurs when someone tries to connect a 3-wire RTD to a 3-wire transmitter using a conveniently available 4-wire cable:ģ-wire RTD measurement is based on the assumption that both current-carrying wires have exactly the same electrical resistance. The following illustrations show both correct and incorrect ways to connect a 2-wire RTD to a 3- or 4-wire transmitter:
![motor winding rtd motor winding rtd](https://meconline.co.za/wp-content/uploads/2020/06/p3.jpg)
This way, the transmitter is able to “look past” the voltage drops of the current-carrying wires to “see” the voltage dropped only by the RTD itself. The only way to do this is to ensure the sensing (non-current-carrying) wire(s) extend from the transmitter terminal(s) all the way to the sensor itself. With any luck, the following presentation will help you avoid such mistakes, and more importantly help you understand why the correct connections are best.Īlways bear in mind the purpose of a 3-wire or a 4-wire RTD connection: to avoid inaccuracies caused by voltage drops along the current-carrying wires. Misconceptions surrounding proper RTD connections unfortunately abound both in students and in working industry professionals.
#Motor winding rtd plus
If the transmitter’s sensing terminal(s) are only jumpered to a current carrying terminal, the transmitter will sense voltage dropped by the RTD plus voltage dropped by the current-carrying wire(s), leading to falsely high temperature indications. The whole purpose of having 3-wire and 4-wire RTD circuits is to eliminate errors due to voltage drop along the current-carrying wires, and this can only be realized if the “sensing” wire(s) extend out to the RTD itself and connect there. It is critically important to note that the common connections shown by the symbols for 3- and 4-wire RTD sensors represent junction points at the sensor not terminals jumpered by the technician at the time of installation, and not internal jumpers inside the transmitter.
![motor winding rtd motor winding rtd](http://i00.i.aliimg.com/img/pb/055/228/429/429228055_467.jpg)
Proper connections for all three types of RTD sensor (2-wire, 3-wire, and 4-wire) to a user configurable transmitter are shown in the following illustrations: