XTR115: How do i give current sense transformer output(1-2V AC) to as XTR115 input?

Hi Winiston,

if you want to get a DC output voltage, you should rectify and low pass filter the AC sensor signal. Is this what you want?

Kai

Hi Kai,

Yes,Basically i want to convert Sensor's AC (1V AC) signal  to DC signal.  Since sensor output is maximum of 1V AC, bridge rectifier loose some voltage due to forward voltage of diode. The forward voltage of bridge rectifier is around 0.7V. So i will loose 0.7V of sensor signal.

Is there any better practice to convert low voltage AC (Max of 1v AC) to DC with out compromising any voltage loss?

Regards,

Winiston.p

Dear Kai,

Thanks for your quick reply. I plan to use OPA322 with XTR115 (4-20mA cuurent loop transmitter). I hope OPA322 is unity gain.

Let me explain my design concept. It is a current measurement design. Primary current is passing through Current transformer. Output of current transformer (0-1V AC) applied to input of OPA322. I expect 0-1V DC from OPA322 and 0-1V DC is again fed to XTR115 which has current gain of 100. Finally i will get 4-20mA output from XTR115 based on primary current variation at current transformer. Please find my attached schematic. Current measurement Schematic.pdf and look at circle marked area for queries.

Is this schematic correct for my application?

My question are given below.

1. AC signals are measured across R19. So it is not reference to ground.. How do i feed it to OPA322 ?

2.Output of OPA322 is pulsating DC(contain AC and DC). Is it required to add filter capacitor(C23) to make it smooth DC?

Regards,
Winiston.P

Hi Kai,

I am still waiting for your response. Please refer my reply.

Thanks & Regards,
Winiston.P

Hi Arockia,

you could do the rectification in this way. It's not ultra precise but simple:

arockia_xtr115.TSC

Kai

Dear Kai,

Thanks for your info. What is the maximum input it can accept at input of OP-AMP-TLV9002S (VF3) as per your above design? Does this design tested one ?

Regards,

Winiston.P

Dear Kai,

Thanks very much for your info. What is the minimum and maximum input/voltage, it can accept at input of OP-AMP-TLV9002S (VF3) as per your above design?  Does this design tested one ?

Regards,

Winiston.P

Hi Arockia,

does it work? Do you have any further questions?

Kai

Hi Kai,

Now i am interested in above simple circuit to convert AC to DC and  plan to use one smoothing capacitor(22uf tantalum) at the output Side (VF1) to convert DC. I hope that it serves the purpose. Ultimately i need to convert AC to DC signal. Since i am designing PCB, i have not yet tested above design. Have you tested above design? How did you get the above waveform ?

You applied 1V AC signal and tested.

I want to know what is minimum and maximum AC signal we can feed to VF3 and converts into DC?

Regards,

Winiston.P

Hi Arockia,

Thanks much for Kai's detailed explanation and simulation.  

If your questions were answered, please let us know.

Best,

Raymond

Hi Kai,

Thanks for your time and support. I added above design in my pcb. Now it is in design stage. So i can only give a feedback once pcb is fully manufactured. I will let you know the status soon.

Thanks,

Winiston.P

Hi Raymond,

Of course my questions were  answered. Thanks for her time and support.

Regards,

Winiston.P

Good luck, Winiston :-)

Kai