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Decoding the EI1050 using a U3


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#1 Ralph1

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Posted 12 February 2015 - 03:46 AM

I am using VB to operate the U3 and have attached the program subroutine.  This uses high level commands and works OK.  The U3 also measures and outputs its internal temperature and it measures an analogue voltage.

 

The problem I have is that the routine (which is a timer  and runs every 20 seconds) consumes a great deal of CPU time and the result is that some pulses which are supposed to be read by another faster timer routine are missed. I do not know why the EI1050 probe takes so long to output its data or perhaps this is because I am using high level commands? I suspect that the CPU is grabbed for at least half a second because that is the time during which the pulses are missed.  They are only missed occasionally but it is vital that every one should be accounted for.

 

Is there any other way of reading the EI1050 which would speed up the operation? The routine I am using is attached. The routine to open the U3 is not shown.



#2 LabJack Support

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Posted 12 February 2015 - 10:47 AM

 

the EI1050 probe takes so long to output its data

The EI-1050 uses a SHT-11 sensor which takes a while to get new readings, depending on resolution.

 

From pg. 6 of the SHT11 datasheet:

"After issuing a measurement command (‘00000101’ for relative humidity, ‘00000011’ for temperature) the controller has to wait for the measurement to complete. This takes a maximum of 20/80/320 ms for a 8/12/14bit measurement. The time varies with the speed of the internal oscillator and can be lower by up to 30%."  So, at 14 bits of resolution, and adding the 30% overhead, this would total 416ms, which is about a half second.

 

 

 

Is there any other way of reading the EI1050 which would speed up the operation?

The LabJack will be blocked for the full ~400ms, but the CPU is only blocked based on your code.  You can write your code in a threaded way to make it so the other process can run simultaneously/asynchronously with the LabJack EI-1050 calls.




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