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# Why you need 250 ohm resistor in hart?

Updated: 8/11/2023

Wiki User

13y ago

The resistor doesn't have to be 250 Ohms, anything from 100-600 will work equally well. The power supply is a low impedance to the hart signal shorting it out. Adding the resistor raises the impedance so that the signal can be detected by the calibrator. A small reactor would also work.

Ohms law states that a resistor must be present with current to receive a voltage (V=IR) this resistor converts current to voltage which is used as a digital voltage signal. (1-5 V).

The HART protocol uses 1200 baud Frequency Shift Keying (FSK) based on the Bell 202 standard to superimpose digital information on the conventional four to 2OmA analogue signal.

Hope this may help ful....

Sudhan.S

shansudhan@rediffmail.com

Wiki User

12y ago

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Q: Why you need 250 ohm resistor in hart?
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### Why you use 250 Ohm resistor in series with HART protocol communication?

You need to use the 250 Ohm resistor in series with HART protocol communication because it acts as a shunt resistor.

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