USB 2408 9-16 load cells

[Mare]

I would like to connect at least 9 load cells to USB-2408-2AO. If I'm right, this module has 8DIFF/16SE analog voltage inputs, so I have to:

1. use external amplifiers for load cells
2. use external power source for those amplifiers, as 2408 cannot provide sufficient power

As I'm not familiar with SE and with the external amplifiers and power sources, please check the example of wiring layout for 2 load cells.

  Amplifier specs: http://www.sah.rs/media/sah/techdocs/tda-01_manual.pdf

 

[DAQman]

Your wiring diagram looks correct for channels 0 & 8. If you wanted channels 0 & 1, connect the second to pin 7 instead of 2. 

Ideally, all nine load cells should be powered by a single supply to reduce the risk of a ground loop.

[Mare]

On 11/21/2023 at 4:16 PM, JRys said:

Your wiring diagram looks correct for channels 0 & 8. If you wanted channels 0 & 1, connect the second to pin 7 instead of 2. 

Ideally, all nine load cells should be powered by a single supply to reduce the risk of a ground loop.

Thanks for your quick reply. I just saw on YouTube on (Measurement Computing's channel) a video of connecting the load cell with mV/V output directly to the USB-2408 (without external transmitter/amplifier). I thought this module is not for bridge based transducers (mV/V)? That's why I added external amplifiers.

 

[DAQman]

The +V terminal found on the USB-2408 can source up to 10mA, which is not enough for your application.

The video used a 700-ohm load cell to keep the current under 10mA.  Utilizing a signal conditioner to power it and amplify the signal is the correct approach. 

[silvia]

hello,

I am a student and in my project I need to do something similar to Mare.

If I use load cells with a resistance high enough to keep the current under 10 mA, it will be correct to connect them directly to the USB-2408? Or this is not possible and I need to use external amplifiers? 

[Fausto]

Hello @silvia.

The +5V terminal (pin 40) found on the USB-2408 is not enough for your load cell's recommended excitation requirement of 10V.  You will need to connect a suitable external power supply to the excitation lines on your load cell.

Regards,

Fausto