Today is...
Wednesday, January 16, 2019
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
EtherCAT with CTC’s master lets your multivendor network play well together...
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
AC Resistance with Low DC Voltage Drop
How to have AC resistance different from DC resistance and low DC drop

Hi all,

I am working on designing a control board which contains HART communication. My problem is that in my board there should be some zener diodes.

Let's assume this diodes are 12 & 16 volts, so the difference is 4 volts. In case of loop current = 20 mA, we can have maximum 4/20=200 ohm of resistance in series, but I need minimum of 450 ohm resistance to make my HART signal sensible.

There is where I have trouble. I need to have ac resistance in order of 400 ohm (frequency is around 1200-2200 Hz) but with dc voltage drop less than 4 volts in 20 mA.

Can you help me?

By Curt Wuollet on 28 June, 2018 - 11:40 pm

Sounds like an inductor or better, a transformer with a loaded secondary.

Regards
Cww