How to Choose Instrument Cables for My Cables

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We have used cables such as these many times on our process skids where I work. Examples are Belden 1032A which is a true twisted pair with a drain wire under the shield for easy connection or Lutze A3091802 which is a pair but not twisted, also with a drain wire for connecting the shield to ground. both are AWG 18 which is a good size for instrumentation as long as you are not trying to run thousands of meters. I am not promoting these manufacturers. Many other manufacuters also make these cables. The references will give you a cross over number to choose a similar cable from your chosen manufacturer.

http://www.texcan.com/products/instrument-and-thermocouple.htm

Twisted pair wires with a shield are available. If your instruments have a guard, then the shield should be tied to guard. If no guard or ground, then tie it to low. A ground should be used on one end only to avoid a ground loop. Typically the shield should be tied to guard and ground on the AC source if using one. The best book I have seen on this subject is Noise Reduction Techniques in Electronic Systems by Henry W. Ott.

I Agree with StandardsGuy Reference with Henry Ott's Book "Noise Reduction Techniques in Electonic Circuits", as being one of the Best References on this Subject. Another Book would be "Measurement Engineering: Basic Principles Volume I" By Peter K. Stein. There are also "Smith Charts" that can be extremely usefull.

This entire Subject Area, to me "Is an Art & a Science". I have been playing in this area for 40 years & I still discover unique situations/criteria.

I look at certain chacteristics such as Analog or Digital, Voltage, Current & Especially Frequency, along with the Input/Output Impedances. I believe that Low Level Low Frequency Analog (ie LLLFA) is the "Trickiest". This is the Most Senitive Scenario for "Gound Loops" with their Instability & Measurement Errors, but Cable Capacitance is Very Important & Must be "Balanced" in Certain Situations (ie C-BAL).

Peter K. Stien in his Book Develops His 'Unified Approach', which uses a 5-Terminal Network for Discovering which Twisted Pair & Shielding/Guarding Scenario is Best & How to C-Balance Cabling. Paul