Hellou!

I having big problems when using Datataker to Loadcell measurements. Loadcell has been calibrated so, that when using 10 V excitation voltage the linear gauge factor is 99,453 kN/mV. Now we get numbers between 600-1000 mV and there are no scaling factor during measurement. Loadcell should give numbers between 0-2 mV, because the calibration area is that. What can be wrong? The loadcell should be ok, because the manufacturer has been calibrated it. In datataker the regulated supply is 5V.

Need some prof. help.

Juha

Hi Juha,

Wheatstone bridge is used for load cell measurement and dataTaker return the value in ratio-metric form (ratio output voltage to input voltage multiply by 1 million) of part per million (ppm). The number you got is in ppm and you need to convert that value into your requirement.

Could you provide me more detail about your configuration (your code)? And what is your choice of channel?

Best regards,
Rudy Gunawan

Hi,

Here is some information about calibration and measurements. We haven't figure out what is wrong in our setups/measurements. Don't understand eather why in SN3439 and SN3442 (=loadcells serial numbers) results are so "big". If you can help us I really appreciate that.

Juha

Hi Juha,

You probably use the wrong channel and configuration.
Could you send me your dataTaker code for review?

I may suggest you the following configuration:

For SN3442:
If you use terminal 1 of analogue channel, then the wiring configuration as follows:
Red (+excitation) go into 1*
Black(-excitation) go into 1#
Green(+output) go into 1+
White(-output) go into 1-

And the code for the above configurations as follows:

'measure a current bridge and save the result into channel variable 1 (1CV)
1BGI(4W,=1CV)

You will get the result in ppm.
Your sensor indicates rated output of 2.011 mV/V @ 2000 kN which mean 2011 ppm for 2000 kN (1ppm= 2000/2011)
Then you need to convert that result using the following code:

'assign channel variable 2 (2CV) for multiplication channel variable 1 (1CV) with the factor of 2000/2011, add title "Load" and measurement unit "kN"
2CV("Load~kN")=1CV*(2000/2011)

You may do the same for the other sensor.

Best regards,
Rudy Gunawan

Hi Rudy!

Can you send me your email (I send you the file)? I also put data here. Our supplier has been made configuration so I don't think that is wrong but now we have to check also everything about logger and wiring. Load cell measurements are part of my thesis and I hope we get results of force-measurements later. Supplier claim that we have broken the load cell, but I think that is not the truth. The measurements went wrong immediately when we installed the load cells and we have done everything as the manual showed.

I'll ask the details of wiring soon and post what was the position of those.

Best regards,
Juha

Hi Juha,

I saw that you are using BGV (voltage bridge) for measuring the load cell.
I recommend you to use BGI (current bridge) because it is less susceptible to electrical noise and not affected by cable length.

I have some comments for your code:

• Your code seems OK, your supplier was using BGV setting and measure output voltage (it was referred from page 298 of DT8x manual). S/N: 3442 is connected to terminal 1 and S/N: 3439 is connected to terminal 2.
• Did you get a direct measurement from BGV in ppm? (Your ppm reading in the picture is coming from vibrating wire).
• Did you use external excitation supply for your load cell?
• Could you test my short code of 1BGI(4W) using command line (access to command line from dEX through Monitor the Logger - Command) and check the result?

I will contact your email tomorrow.
Btw, I still need your wiring diagram (you can send it to my email address tomorrow).

Best regards,
Rudy Gunawan

Hi Rudy,

I will write here or to your email, when I get the information about wiring etc. The logger and load cells are 200 km away from here and I try to get all information from colleague as soon as possible. We didn't use any external excitation. Those load cells was meant to use BGV and I've been interviewed different people and they been recommended to use load cells that has been made for BGI. In this case I wasn't the mastermind who purchased those items but still we need to figure out what is wrong with these setting etc. One plan was to test those load cells with different loads in laboratory and check that everything is ok but now its too late because load cells are now part of sheet pile wall. The vibrating wire setup was for the temperature measurements with different item (sorry I forget to tell that before).

I'll send you missing details later when I get them.

Best regards,
Juha

Good morning Juha,

Load cells are not "Made for Voltage excitation" or "Made for current excitation" any load cell will work with both.
The advantage of current excitation is that you will not get signal loss due to lead length in the way you do with Voltage excitation.

If you are using Voltage excitation then you need to read the bridge reference voltage to allow for lead length losses.

Cheers

Roger

Hi!

I have been sent material for you Roger!

Cheers

Juha

Hi Juha,

I haven't seen you documentation yet. Did you send it the the AU support email address?

Cheers

Roger

Hi all,

This topic has been brought outside the forum.

Best regards,
Rudy Gunawan