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Sensor wiring / Calibrating


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#1 evendol

evendol
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  • 9 posts

Posted 02 October 2012 - 12:40 PM

Hi,

Iíve posted before about reading out a Balluff sensor with the U6
This is the sensor: http://www.balluff.c...E_EN_145577.pdf

This sensor has a stroke of about 800 mm. When I restart my machine
I get an error of 0,3mm (= +/- 0,008 Volt).
When I recalibrate it reaches around 0,05mm repeatability, which I think is very good!

Now I am building a 3rd machine I have following questions:

1. What is the optimum cable to use for this?
I now use 12 x0,75 mm2 but plan to use 12x 0,5 mm2 shielded cable?

2. What kind of current can be expected in this measurement?
I can imagine that the measuring difference of 0,3mm can be caused by
change of wire resistance with changing temperature.

Thanks,


Evendol

#2 LabJack Support

LabJack Support
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  • 8677 posts

Posted 03 October 2012 - 07:39 AM

1. I would not expect the cable to make much difference. I suggest you do a test with a very short heavy duty cable, and see if the readings are any different than what you see with a long thin cable.

2. I assume you connect a power supply to pins 6 & 7, then connect pin 2 to GND on the U6 and pin 3 or 5 to AINx on the U6. Then you should only have the analog input bias current flowing on in/out of the GND and AINx terminals, which is on the order of 20nA:

http://labjack.com/s...uide/appendix-a


If you have some sort of ground loop issue, you could have more current flowing in/out of the GND terminal, and perhaps that could cause a problem. Use the test in #1 above to see if this is even a problem.

The CB37 datasheet discusses this:

http://labjack.com/s...rs-guide/2.11.1


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