I tried to interface HART modem AD5700 with DAC161S997 for getting the HART FSK signal from loop current. By using 250ohm connected series with loop supply will only give voltage drop across resistor for varying loop current. Then how can i measure/differentiate the HART FSK signal from loop current?

 

The HART data is a digital FSK signal that you will find on pins of the AD5700 chip. You do not need to worry about separating the analog signal from the HART FSK - that is the job of the AD5700 chip. In order to route this signal to your DAC, you should consult the wiring diagram on the AD5700 Application Data Sheet that you can see at this site: http://www.analog.com/en/products/i...loop-interface-devices/hart-modem/ad5700.html

Look at Fig. 31.

Most of the information you will need can be found by doing a web search. This did not take very long to find. I suggest you search the web before asking questions such as this.

>I tried to interface HART modem AD5700 with DAC161S997 for
>getting the HART FSK signal from loop current. By using
>250ohm connected series with loop supply will only give
>voltage drop across resistor for varying loop current. Then
>how can i measure/differentiate the HART FSK signal from
>loop current?

 

Differentiating the HART FSK signal on the loop is the HART modem's job (the AD5700 device, in this example). The HART modem converts the frequency information to digital ones and zeroes, a 1.2 kHz signal represents a digital 1.

Typically, a HART modem is connected to a microcontroller or other processor via a UART [serial port], which can assemble a series of digital 1s and 0s [bits] to form bytes.

 

I want to know if AD5700 interfaced with DAC161S997, Whether the HART FSK output signal from DAC can be observed on the oscilloscope along with the loop current? If it is not, then how can i determine whether the hart data is coming out from DAC?

 

> (Can) the HART FSK output signal from DAC can be observed on the oscilloscope?

When it's there, yes. But it's probably not unless you have a HART master polling the slave-ship.

A standalone Hart-enabled AI chip does not broadcast HART data.

HART is a master-slave protocol and the slave/chip will only respond to a properly formatted request from a master. I can't recall what 'burst' mode is off the top of my head; it might enable some form of broadcast, but would have to be triggered first by the master.

Unless you have a master polling the slave-chip, there will be no HART data on the 4-20mA signal.

 

An AC coupled amplifier and a FSK detector come to mind. No simple way short of a HART receiver of some sort.

Regards
cww

 

Yes, you should be able to see that.

Regards
cww