XTR115: AC Input Signal

Hello Alexandre,

Can you send me LTSpice simulation if you are able? I can take a look at it. 

Is the sensor picking up ambient 60Hz noise and get into the front end of the circuit? 

Regards,

Raymond

Hello Alexandre,

Have you tried AC high pass filtering or simply provide shielding along the input of sensor input? 

Regards,

Raymond

I'm not trying to remove the AC component as what I want to read with the XTR115 is a 60Hz AC signal. Can the XTR115 read an AC signal directly or must it be converted into the positive range only? 

Hi Alexandre,

Please see the attached Tina schematics, which I made some comments per your AC input signal issues (made some assumption). The input Op Amp A1 has frequency response up to 380kHz, and will work with 60Hz AC input signal.  

If you have further questions, please send us a simulation or schematic, and we can address your issues more specifically.  

Regards, 

Raymond

XTR115 60Hz AC + 1V DC input 10112019.TSC

Hi Alexandre,

Additional Information:

XTR115 is 2-wire transmitter. The Iret pin can not connect to GND - internal regulator and input circuitry have to float.  

XTR117 is 3-wire transmitter: XTR117 does not have the "GND" issues. 

Attached ppt for your references. 

Regards,

Raymond

0435.4-20mA_Basics.pdf

Additional Links in 4-20mA Sensor Transmitters. 

XTR117 is 2-wire transmitter. XTR111 is 3-wire transmitter.

https://e2e.ti.com/blogs_/b/precisionhub/archive/2014/12/09/part-2-two-wire-4-20-ma-transmitters-background-and-common-issues

https://e2e.ti.com/blogs_/b/precisionhub/archive/2015/01/13/two-wire-4-20ma-transmitters-background-and-common-issues-part-3

Also, there are 4-wire, fully isolated transmitters.

Regards,

Raymond

Thank you kindly for the TINA schematic, this is very helpful!

Might I ask which Op Amp would be suitable for this application ?

Hi Alexandre,

Can you provide me more information about your sensor? I will be happy to specify an Op Amp per your application.  

I'd like to know the sensor's design requirements  in operating voltage range (single or dual supply), sensor type, expected Gains, Operating temperature range, expected Min. and Max. Voltage and Current errors, desired CMRR, bandwidth, current bias information, desired S/N ratio, temperature drift Information, Response time etc.. Also, it will be good to know what package size you would like. 

Regards,

Raymond 

The sensor doesn't require any external power and doesn't have any gain. Voltage output is customizable but currently looking in the 0 to 0.25V range. Operating temperature range is -50C to +105C. I'd like to keep the voltage error below 0.15% with a response time of 8ms or better. Package size is not important, there is plenty of room.

Thank you!

Hi Alexandre,

I did some searching per your application requirements. Here is what I came up with, no particular order. 

1. OPA188

2. OPA221

3. OPA333

4. INA317 (-40C to +125C)

Please let me know if these will meet your need. 

Regards,

Raymond