I'm thinking about controlling a valve for fan coil coolant from a distance of approximately 10 meters.

The control signal is 0-10V, and the impedance of the regulator is stated to be 100k ohm.

Let's say I provide 5V in at one end of this wire. In a typical residential environment, what will be the observed voltage at the other end when loaded with 100k ohm?

Will I see ripple of 10s of mV, 100s? Even volts?

Let's say the cable goes parallell with 230V wires for many meters, and someone is opeating a household mixer nearby the cable, for example.

  • \$\begingroup\$ Depends a fair bit on where (as in "what circuit") the control signal comes from. Not so much on the load. \$\endgroup\$ – Spehro Pefhany May 5 '15 at 17:24

If you use twisted-pair cable, you should have no problems. I would even go so far as to use shielded twisted-pair cable but I'm an audio guy, so I naturally think that way.

If the person who designed the electronics in the valve was even remotely competent, induced AC mains pickup in the control signal should be either filtered or integrated out and would normally not cause any problems.

To figure out what the voltage at the end of the wire would be, you need to know the DC resistance of the cable as well as the terminating impedance / resistance. Because you say that the valve controller presents a load of 100k Ohms and you are using copper wire, you can safely assume that the voltage drop in the cable is not measurable and you will see whatever voltage you apply at both ends of the cable.

If you are running the control cable parallel to a high-voltage AC Mains cable, using shielded twisted-pair cable should eliminate any possible induced pickup.

  • 1
    \$\begingroup\$ Agree, industrially, we use shielded twisted pair cable (foil shield, not necessarily braided) here for all 10V analog signals, up to 1000 feet with no issues. And that is in a bad environment, not always with proper (or any) spacing to power cables. As long as the load has a high enough resistance that the cable resistance is negligible, you should be fine. \$\endgroup\$ – R Drast May 5 '15 at 17:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.