LJStreamM Second Channel Voltage Drop | LabJack
 

LJStreamM Second Channel Voltage Drop

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Diego Luna
Daniel Park's picture
LJStreamM Second Channel Voltage Drop

Hi,

I have tested two ADXL354 accelerometer using Labjack T7-Pro, sampling rate 1000 Hz.

When only AIN0 channel is selected, the voltage output has no problem. 

However, when AIN0, AIN2 channel are selected and push the start stream button,

AIN2 voltage output drops suddenly from 0.9V to 0.58V.

After that, unactivate the start stream button, AIN2 voltage output returns from 0.58V to 0.9V. 

(You can check it out in the attached video.)

I would appreciate any advice on a phenomenon like this.

 

 

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LabJack Support
LabJack Support's picture
We would suspect the issue is

We would suspect the issue is related to channel settling time. We specify the maximum source impedance without settling error (under automatic settlings) to be around 1kΩ and the source impedance of the accelerometer appears to be around 32kΩ. The following application note has some additional information and tests:

https://labjack.com/support/app-notes/SettlingTime

Potential solutions for settling error are to increase the settling time using the STREAM_SETTLING_US register or use a buffer like the LJTick-InBuff in front of the inputs.