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Reading Signals

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#1 GVS

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Posted 31 May 2013 - 05:46 PM

I'm new to the LabJack U6 and I need to wire an encoder(EMS22P50 B28-LS6 Encoder), pressure transducer, hall effect sensor, and potentiometer and read signals from an apparatus that oscillates at varying frequencies and RPMs. My current set up: - Encoder's signal wire connected to FIO0 - Pressure Transducer's signal wire connected to AIN0 (static pressure) and AIN1 (dynamic pressure) - Hall Effect Sensor's signal wire not connected to anything (don't know where to connect it to) - Potentiometer's signal wire connected to AIN3 All sensors are powered externally by a 5V power source Using the LJStreamUD: When the apparatus rotates with a certain RPM and frequency, the voltage doesn't vary on any channel and anything shown on the graph below is very noisy Does anyone have any input as to how to correctly read the signals? Any help will be greatly appreciated

#2 LabJack Support

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Posted 03 June 2013 - 10:02 AM

Start with the test panel in LJControlPanel.

The first thing I notice in your description is that you don't seem to have a common ground reference. Can you power all these sensors from VS on the U6, or do you need to use the external source? To continue using the external source, you need to connect the negative of the source to GND on the U6.

Hall Effect Sensor: Please provide a link to technical details for this sensor.

Encoder: I see this gives a pulse output signal where a 1us pulse equates to 0 degrees and a 1024us pulse equates to 359.65 degrees. Have you considered using the low pass filter shown in the EMS22P datasheet to provide an analog input? That would be a simple way to read this sensor, although with R1=R2=4.7k your source impedance is a little high.

A slightly more complex, but great way to measure the pulse width is use a Timer on the U6 in duty-cycle input mode:


Try the default 48MHz clock with no divisor. With a 48MHz clock, a 1us pulse will give you 48 clock ticks, and a 1024us pulse will give you 49152 ticks.

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