Load Cell configuration

[gregorian7]

Hi.

I've been trying to configured Load Cell with NI9263 for Excitation signal +10VDC and NI9215 to read voltage from Cell. 

Scaling:

0mV - 0LB

19.93mV - 250LB

I don't know what  I'm doing wrong by I can only read very small value after scaling the output signal.

[GerdW]

Hi gregorian,

when your setup fails you should start to RTFM!

The NI9263 will deliver just ±1mA, but your sensor requires 10V/369Ohm=27mA…

Btw. did you even checked the excitation voltage using a simple DMM - or even an additional input channel of the 9215?

[gregorian7]

Hi.

Thanks for your answer.

Sorry I didn't realised that.

Yes, I have checked signal from AO with DMM = 10V. 

But, once I connected sensor into sensor voltage dropped to .69V (voltage across the bridge).

So, I will have to find different power source to run the cell?

Best regards,

Gregorian7

[Borjomy]

You need a Voltage-to-Current converter such as Analog Device 5B39-03 or similar that you connect to your DAC.

links: 5B Series Model Definitions, 5b39

Modules of the same type are manufactured in the form of a device on a DIN-rail

[Henrik_Volkers]

---

@Borjomy wrote:

You need a Voltage-to-Current converter such as Analog Device 5B39-03 or similar that you connect to your DAC.

links: 5B Series Model Definitions, 5b39

Modules of the same type are manufactured in the form of a device on a DIN-rail

---

No, he wants to read a bridge sensor and have a voltage input .. so I suggest a  5b38 🙂

The problem with the 9215 voltage input is the internal 100k to COM (or no problem if the error is acceptable) ... you would need a really floating 10V exitation. You can do a test with a 9V battery as exitation and do a correction... (factor 10/9)

[gregorian7]

Hi guys,

Thx for your help.

Is there any DAQ equipment that would meet this sensor power requirements?

Maybe will be cheaper to get different cell rather than investing more money in equipment?

Cheers

Gregorian7

[Henrik_Volkers]

a 5b38-02 is  <200$/€

and you can find bridge sensor conditioner with 5V supply and voltage output in the 20 bucks range for the maker/DIY/arduino scene ... (and would need a calibration.. )  

what requirements do you have for your force measurement?

[gregorian7]

Hi,

See first post attachments.

10V/389ohm  = 27mA...

Regards

Gregorian7

[Borjomy]

Why is it necessary to exactly 10V and not less?

[GerdW · Accepted solution]

Hi gregorian,

any cheap power source will provide 27mA…

When you need a more accurate voltage level you could buy a 12V power supply and build a small PCB with a 7810 power regulator IC. (With just 2V voltage drop over the IC at <=30mA it will just burn less than 60mW and so will not even need a heat sink when you use the TO220 housing!)

All this will cost less than 20€…

(Or follow Borjomy's advice and use a cheap mobile phone power supply with 5V output…)