NI 9237 conections

[Arthuruuuuuu]

Dear friends,

I am using NI 9237 and RJ50 conector to acquire a signal from a load cel. 

From data sheet, it recommends me to plug the 4 wires that come from load cell in holes number 2 and 3 for excitation and 6 and 7 for acquisition. But still with high levels of noise. I read in data sheet there is an alternative conection but with 6 wires (figure attached). I didnt understand how to connect it because from my load cell only comes up 4 wires instead of 6. Any one can help me ?

Thanks a lot,

Arthur

[Lysandros]

Hi,

consult first your load cell's manual, this will tell you, what the pinout of your sensor is. Generally, the sensor will need an excitation of 2.5V or 3.3V or 5V. The output signal should be in the order of few Millivolts. Also check this link from NI:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000PA73SAG&l=de-DE

Also, the manufacturer of the load cell should state, what the two factors of converting from mV to Nm (or N) are. NI-9237 will return you a raw signal, but you have to apply a multiplication and addition in order to get your load value in Labview.

Best wishes

Lysandros

[Arthuruuuuuu]

Hi  Lysandros, thanks for your answare.

My load cell manual says 2mV/V whith excitation from 10 to 15 V. 

I have already calibrated it to convert mV answares to N. I have already alson seen the link you recommended me. The point is that i dont understand how can i make a different connection with 6 wires if from my load cell only comes 4 wires. 

Sorry, and thanks again,

Arthur.

[Lysandros]

If your load cell has 4 wires, then they are probably

Excitation +, Exicitation -, Analog Output +, Analog Output -  ? If this is the case, you do not have a "Sens" option (which is used, in order to control, what the actual local excitation value is, i.e. if it has droped due to cabling resistance etc), then you do not need a 6 wire connection. Just connect the four load cell wires to the corresponding NI-9237 pins.

[hurch]

Good day
I am to write a code that will read data from two NI 9237 modules (6 channels in total). the modules are to read data from a force balance (strain due to force).

I know its not a matlab community but I could get help, how do I convert strain result to force using a loadcell of specification stated below and the NI 9237. being specific, I need the coefficient to convert strain value given by the daq to force.

Load Cell: STA-7 Aluminum Alloy S Type Low Range Tension/Compression Load Cell

Rated load (kg)                      1, 2, 5, 10, 25, 50
Ultimate breaking load         300% of rated load
Maximum transverse load   <50% of rated load
Output/ Sensitivity                2mV/V (±0.1%)
Zero balance              <±1% of rated load
Excitation voltage                  10vdc recommended, 15vdc maximum

ch6.BridgeMode = 'Full';
ch6.ExcitationVoltage = 10;
ch6.NominalBridgeResistance = 350;