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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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 Posted: Fri Jul 18, 2014 12:12 pm |
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I still say that you need to post your question on the TI forum:
http://e2e.ti.com
In this post here,
http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/296827.aspx
they say:
| Quote: |
Have you tried applying a mid-supply common-mode voltage to both
inputs while shorting them together and checking the stability of the readings? |
This is exactly the noise test that the EVM manual says you should do.
But you are not doing this test. You are doing this:
| Quote: |
I tried removing the long wires I had coming off of the AIN0 and AIN1
inputs and soldered a resistor lead across the inputs and noticed my
output went very close to zero, however I'm still getting a random spike
in the data which i found very strange.
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Log on to the TI board and post your problem in detail, with schematics
and a photo of the board and test setup.
The TI forum response continues:
| Quote: | Your input source may not be stable, therefore, the shorted input test will tell you the highest repeatability you can achieve with your system.
If the voltage reading is still unstable with shorted inputs then you'll have to debug where the source of noise is...
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In this thread here,
http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/68797.aspx?pi239031349=1
they say this:
| Quote: |
One thing to consider is even if you short the inputs, the inputs can pick
up noise if it is being generated in the area, especially if they are floating,
or are connected to long traces. Even if the inputs are connected to
ground, there can be ground instability. |
They know a lot more than we do, because the ads1255 is their product !
Ask them about it.
This is probably the best one to post in: The Precision Data Converters forum.
http://e2e.ti.com/support/data_converters/precision_data_converters/default.aspx |
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