Hello,
Currently, I am using Lab Jack U6 to record two amprometry gas sensors via LabView. I will need to optimize the signal output before optimizing the sensor responses to the target gases. I started with changing the resolution, while the other factors such as gain and settling time were kept at the default value (gain 1X and settling time 0). I first got all the responses in each resolution (time in each step was kept constant, 3min) while the sensor was exposed to Air/ the target gas and calculate the Signal to Noise ratio(SNR). I could see the first 1,2,3 and4 values are much larger than other resolution values. However, I am not sure what is the next step and is it enough to optimize the recorded output signal by LabJack. I have attached pictures of my VI of my sensor loop and Sub-VI related to the Lab Jack setting. I appreciate if you could advise me how and from which factors I should start and optimize the output of my sensors signals.
Best regards
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What are you trying to optimize for? Measurement resolution, timing accuracy, acquisition speed?
There is always going to be some tradeoff between the measurement resolution and maximum acquisition speed. If you need higher resolution increase the resolution index and use a higher gain/range setting, or do the inverse if you need higher sampling speeds. If you need speeds faster than ~100 samples/second or better timing accuracy we would recommend using stream mode acquisition. Our operations datasheet section has additional information about stream mode:
https://labjack.com/support/datasheets/u6/operation
Thank you very much for the prompt response. I actually need to optimize the resolution of my readings, and I tried to start with this factor. As the gas sensor output is between 0 to 3V, if I understood it well, I only could choose Gain/Range 1 (10V).
Also, I appreciate if you could answer my question about how to calculate sampling rate (Hz). I am checking the sampling rate at the sensor SNR, but I am a bit confused. I was wondering what is the sampling rate (1/T) when I am using resolution 1 and averaging 500 sample/s. The actual waiting time for each reading in this situation is about 0.7 sec. and I am recording the reading data from LabJack each 0.5 sec into a text file. Thanks
You are correct about the gain setting. The next available gain is x10 (±1V) so you must use the ±10V range.
If you are not using stream mode, your sampling rate is dependent on your software and limited by how quickly you can get through your acquisition loop. Assuming your loop only contains AIN reads, the acquisition time should follow a formula similar to:
CRT (milliseconds) = overhead + (#AINs * AIN Sample Time)
The overhead and AIN sample time values are described in greater detail on the following page:
https://labjack.com/support/datasheets/u6/operation/command-response
I would also like to note that increasing the resolution index does oversampling and averaging internally to help increase resolution, so we recommend increasing the resolution index before oversampling in software. Additionally, if you have a U6-Pro the resolution indices 9-12 use a higher resolution ADC that has good low frequency noise rejection.
Many thanks for your support!