UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

cancel
Showing results for 
Search instead for 
Did you mean: 
Observer cole.jepson
Observer
3,682 Views
Registered: ‎01-23-2017

XADC Voltage Not Accurate

Jump to solution

I've followed this awesome example given by mhkang64 at http://zynqhowto.blogspot.com/2014/03/zynq-how-tolab3.html

and it works, but it doesn't give the best accuracy. Every two or three samples gives a voltage reading that is about 0.3 volts lower than it should (sample rate of once per 5 seconds). I am using a DC voltage source fed into the XADC (so I know the voltage is stable). I was wondering if this is a common problem and if you could direct me to an easy fix for this or a good article about how to get better readings off a Zybo board XADC. Currently, I specified channel averaging of 16 in the Vivado xadc wizard block (what does this actually do?). 

0 Kudos
1 Solution

Accepted Solutions
Scholar austin
Scholar
6,840 Views
Registered: ‎02-27-2008

Re: XADC Voltage Not Accurate

Jump to solution

I suggest you check your voltage source,

 

The sample and hold on the XADC can see transients as fast as 1 ns.

 

Maybe put a bypass cap across the +/- inputs t6o filter out any noise?

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose

View solution in original post

3 Replies
Scholar austin
Scholar
6,841 Views
Registered: ‎02-27-2008

Re: XADC Voltage Not Accurate

Jump to solution

I suggest you check your voltage source,

 

The sample and hold on the XADC can see transients as fast as 1 ns.

 

Maybe put a bypass cap across the +/- inputs t6o filter out any noise?

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose

View solution in original post

Observer cole.jepson
Observer
3,613 Views
Registered: ‎01-23-2017

Re: XADC Voltage Not Accurate

Jump to solution

I have a nice benchtop multimeter hooked up to the same input as the voltage source so I'm pretty sure the source is accurate but I'll try a small cap. Thanks for the tip.

0 Kudos
Scholar u4223374
Scholar
3,601 Views
Registered: ‎04-26-2015

Re: XADC Voltage Not Accurate

Jump to solution

Multimeters tend to do a lot of smoothing of the input; they're very accurate when the signal is steady but they're not designed to catch transients (which will definitely cause odd data on the ADC). For that sort of thing you need an oscilloscope.

 

You could try using a battery as the source (eg. a single AA with a voltage divider to cut it down to under 1V). That should be extremely stable.