6403D ADC Voltage

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Posts: 2
Joined: Fri Dec 01, 2017 1:32 pm

6403D ADC Voltage

Post by MisterT » Thu Jul 19, 2018 11:42 am

Hello ,

I'm trying to make sense of the ADC vert scaling. The specs seem to state a 6403D has 8bit vertical resolution but with 12bit enhanced.

When I use the LabView streaming example the graph is plotted with 16-bit ADC counts. Is this correct for my unit ?

However when I input a 1V DC signal it reads around 32400 counts (plus some noise) which doesn't seem to relate to 8/12 or 16 bits ?

I want to be able to accurately extract the pk-pk waveform levels and so far I can't get a DC level to read back correctly.

Can someone explain what my specific unit can obtain and why the LabView examples don't appear to work correctly. Hopefully I am missing something obvious !!

Many thanks.

Posts: 251
Joined: Tue Oct 21, 2014 3:07 pm

Re: 6403D ADC Voltage

Post by AndrewA » Thu Jul 26, 2018 10:43 am


The 6403D has 8-bit ADCs, but the driver returns scaled 16-bit data types (int16_t) (This is the case with all our 8-bit scopes)
See page 4 of the users guide for max and min ADC values.
https://www.picotech.com/download/manua ... -guide.pdf
So as you said 1V DC signal it reads around 32400 counts (1V range)
So covert this to 8-bit number- (32400 / 256 = 126.56) round upto 127 is 0x7F hex, which is max ADC value when converted back(0x7F00 hex)
Having the 16-bit data types allows for calibration scaling to be applied to ADC counts, before returning values to the user.

I have changed the block example, that uses our ADC to volts.vi. It needs the max ADC count value, the channel voltage range, to work.
These should be updated today, on github.
https://github.com/picotech/picosdk-ni- ... leBlock.vi
https://github.com/picotech/picosdk-ni- ... leBlock.vi

Please use the correct version of SDK and LabVIEW. Meaning 32-bit or 64-bit for both. Note you can install both versions of the SDK.
Regards Andrew
Technical Specialist

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