AD 7193, Noise Count Histogram

Hi Michael,

Sorry for the delayed response.

Output rate of 2400hz means that there is no prior averaging. 

Could you give more info on the setup and load cell being used? 

Regards

Vikas J

Hello!
in the meanwhile I changed my setup to better understand whats going on in my circuit.

I disconnected the Load cell to check if my ADC without loadcell is doing well.
I would like to get anywhere close this histogram:

My values (with Averaging:1, chop dis, sin4, Ain1&Ain2 shorted) look like this:
 
(Scale y: 0, 400, 800)

As you can see (or maybe cannot see because of the bad upload quality) most of the values are between 0 and 400, some are even 800 counts off. So i guess i´m doing something wrong? I measure fully differential (tried pseudo aswell but the problems stays the same) My noise is way to high in comparison the the datasheet histogram.

Am I naive to think I could reproduce the histogram of the datasheet? Is this some crazy vacuum lab setup which they show in the datasheet?

As written I am using an Digileng Pmod AD5 with an AD7193 onboard. (Schematic)
The digilent board has an onboard Vref "generator" ADR441 with 1.2 μV p-p noise.


So:
Vref (ADR441) of the ADC is supplied to Refin1,
VDD is supplied via Arduino
A1&A2 are tied together
AVDD comes from an LT3042 (3.3v) - my values dont change even if i tie AVDD with VDD.

In my final application (loadcell) I would like to conduct a Ratiometric measurement:

 i am using this libary to interface Arduino <-> Pmod via SPI

Thanks for your help in advance 

Hi Michael,

I am seeing the data between 0-800 (negative peak) while the shorted input for differential mode needs to be around midscale (1000...). I would suggest you to first verify that SPI is working fine. Say, you make some changes to the register and read back or  read a non Zero register. It would be helpful if you can share the register map with us.

Once we are sure the device is configured correctly, then we can debug the noise related issues. 

Regards

Vikas J

Hi Michael,

I am seeing the data between 0-800 (negative peak) while the shorted input for differential mode needs to be around midscale (1000...). I would suggest you to first verify that SPI is working fine. Say, you make some changes to the register and read back or  read a non Zero register. It would be helpful if you can share the register map with us.

Once we are sure the device is configured correctly, then we can debug the noise related issues. 

Regards

Vikas J

I made a calibration at the beginning of the programm and then subtracted the following measurements to get values around 0. If I stop doing that, my values are around midscale 
If i stop doing this my values look like this: ~ 8388700 ..
My communication is working my Registers with Gain 1 look like this:

After changing gain to 128 changes to 117:

My resulting Histogramm looks like this:


Edit:
I finally got my setup working with acceptable noise (very close to the noise in the datasheet)
I had to edit the GIT Libary:

AD7193.cpp
0x800100 instead of 0x800000

When conducting a Full scale calibration i had to specify the channel:

Thanks for your help!

Hi Michael,

Glad to know that it is working as per the requirement. 

Thanks

Vikas J