How do i set the bits for highest signal to noise ratio at 10kHz correctly? | LabJack
 

How do i set the bits for highest signal to noise ratio at 10kHz correctly?

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boezkaya
boezkaya's picture
How do i set the bits for highest signal to noise ratio at 10kHz correctly?

Hello Labjack-Forum,

my circuit looks like this from another Forum post of mine. https://labjack.com/sites/default/files/forums/Idea_1.png , https://labjack.com/forums/u3/difference-between-my-circuit-and-picture-using-ground-input

1.) I want to sample data with a frequency of 10kHz and i use 2 Analog Inputs ( single-ended, MAX samples/sec = 20000 ).

Im rather confused about my PChannels and NChannels parameters since i use the dedicated AIN0 / AIN1 and GND on my LJ U3

Can you confirm my streamConfig-Parameters and( Python ):

d= u3.U3()

# To learn the if the U3 is an HV
d.configU3()

# For applying the proper calibration to readings.
d.getCalibrationData()

# Set the FIO0 and FIO1 to Analog (d3 = b00000011)
#d.configIO(FIOAnalog=3)

No configIO needed for using the dedicated AIN0 and AIN1 right ?

d.streamConfig(NumChannels=2, PChannels=[31 31], NChannels=[31, 31], Resolution=2, ScanFrequency=10000)

 

2.) I have also heard from other Posts on this forum, that someone got problems with noise and he got suggested to change some Code on the streamTest.py to the following:

d.streamPacketOffset = 0

for r in d.streamData(convert=False):

and then converting it later, instead of

for r in d.streamData():


Are there any other Parameters that i can adjust for best measuring that i should be aware of ? 

Thanking you in Advance,

Benjamin

LabJack Support
LabJack Support's picture
1. PChannel are the positive

1. PChannel are the positive channels and NChannel are the negative channels. Positive channel 31 is the internal Vreg and negative channel 31 is single ended.

If streaming AIN0 and AIN1 single-ended, set PChannels to [0, 1] and keep NChannels as [31, 31]. If using a U3-HV, AIN0-AIN3 are dedicated analog inputs and do not need configIO FIOAnalog configuration.

General analog input channel numbers documentation can be found here:

https://labjack.com/support/datasheets/u3/hardware-description/ain/chann...

2. Setting convert=False does not affect analog input noise, and is a software option for streamData on whether it converts samples to voltages or not. Samples directly from the U3 are a binary value.

streamConfig configures stream mode settings on the device. The Resolution affects resolution/noise. You currently have it set to 2 which is the highest resolution you can set for a 20000 samples/second stream.

General stream mode and resolution documentation can be found here:

https://labjack.com/support/datasheets/u3/operation/stream-mode