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Druck DPI 282 Digital Indicator using 4-20mA Output

Druck DPI 282 4-20mA LJ_tick current shunt current output current shunt

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#1 Hybrid Engineer

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Posted 03 September 2013 - 08:54 AM

Hi all

 

I have a Druck DPI 282 (Digital Process Indicator) measuring water pressure in bar.

 

I am using the current output 4-20 mA which equates to 0-25 Bar. I am connecting it through a LJ_Tick Current Shunt. When I run my program I am getting some strange results. The output is slightly higher than expected (around 0.7Bar) this would not be a problem as I could just set an offset but the readings are quite erratic and fluctuate as much as 0.3Bar.

 

Now the strange bit, the reading on the 282 unit itself is consistent and I measured the current coming out of it and its what I expected it to be. I then used a current source to feed the labjack with the same current and the labjack reads a consistent correct value. So the problem only arises when I connect the 282 to the labjack.

 

Any suggestions would be great!

 

Thanks

 

HybridEngineer



#2 LabJack Support

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Posted 03 September 2013 - 09:55 AM

 

 

 ... the reading on the 282 unit itself is consistent and I measured the current coming out of it and its what I expected it to be.

 

Did you use a DVM to measure this current?  What if you put the DVM in series with the current loop at the same time as the LJTick-CurrentShunt?

 

Are you using Figure 4 from the LJTCS datasheet:

 

http://labjack.com/s...shunt/datasheet

 

Do you have INA- jumpered to SGND or GND?



#3 Hybrid Engineer

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Posted 04 September 2013 - 01:38 AM

Thanks! I did not connect INA-1 to SGND for some reason I thought they were connected internally.

 

For reference I did connect a DVM in series with the LJ_TICK Current Shunt and the reading did not change.

 

Thanks for your help.



#4 LabJack Support

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Posted 04 September 2013 - 09:08 AM

So did the SGND connection fix things for you?



#5 Hybrid Engineer

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Posted 09 September 2013 - 07:40 AM

Yes, thanks very much.




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