Calculating the attenuation of a Twisted pair wire

dl324

Joined Mar 30, 2015
8,877
Welcome to AAC!

What type of signal are you sending over the wire, what is the wire length, and what are the source and load impedance?
 

Thread Starter

Daniel9210

Joined Oct 10, 2019
3
Welcome to AAC!

What type of signal are you sending over the wire, what is the wire length, and what are the source and load impedance?
Thank you, Sir. So I have three different sensors that I'm planning to use — one for Temperature, one for Flow, and one for the Pressure. Then I want to use a junction assembly box to connect them to the cable. Also, the length of the cable is 100 feet and its impedance is 52 Ohm.
 

dl324

Joined Mar 30, 2015
8,877
What is the magnitude of the voltages from the sensors? What are you using to read the voltages?
 

Thread Starter

Daniel9210

Joined Oct 10, 2019
3
Maximum 5 volts. I will be using a chip in the junction box to read the data but I haven't picked it yet.
 

Reloadron

Joined Jan 15, 2015
4,501
Thank you, Sir. So I have three different sensors that I'm planning to use — one for Temperature, one for Flow, and one for the Pressure. Then I want to use a junction assembly box to connect them to the cable. Also, the length of the cable is 100 feet and its impedance is 52 Ohm.
Looking at the data sheet for your Belden Part Number: 8723 Audio, Control & Instrument, #22-2pr, PO, Indiv. Foil, PVC Jkt, CM the cable impedance is 52 Ohms. The maximum voltage is 300 volts RMS with a max current capability of 2.3 amps at 25 Deg C. The DC resistance is also included in the data sheet.

So you need to figure if these parameters are suitable for your sensors (application). Your sensors return a signal proportional to what they measure so if you are measuring Temperature, Flow and Pressure your signal from a sensor can be for example a Voltage or Current proportional to what you are measuring. You select the cable based on its intended application and without going too deep I have used the same cable extensively with sensors. Just keep in mind with for example a temperature sensor of an RTD type you need to figure in the cable DC resistance. Knowing the exact sensors and if they require excitation would help?

Anyway, the data sheet is where it all begins. That combined with how your sensors work and what they output.

Ron
 

MrAl

Joined Jun 17, 2014
6,469
Hello there,

You have to specify the operating frequencies to get that figure. If it is low frequency you can often treat it as DC but for higher frequencies (above maybe 20kHz) you have to start thinking in terms of a transmission line and possibly even skin effects. It's best to look up specs for a twisted pair. Ultimately you'll want to make some measurements also.
 
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