Strain Gauge (RB-Onl-38) and Load Cell (RB-Phi-118)

Has this been resolved (robotshop.com/forum/topic-t14246)? I am having the same problem. The output from the AD8426 does not change as pressure is applied. I am applying pressure that will produce a 6mV signal change but I’m not seeing the voltage at the amplifier output or at the A0 output for channel 1 change. The input wires are connected as shown in the blog entry and I have checked to see if the resistance changes on the load cell. This is the first time I’ve used the board. The output from the amplifier is 1.5 v with the potentiometer set half way between limits.

Thanks,
John

Hi,

Can you post a clear picture for your setup ? (Arduino + RB-Onl-38 + Load Cell)
Did you verify in the code that you are reading from A0 pin for Strain 1 ?
Could you try to vary the voltage reference pot for Strain 1 ?

Regards,

http://i50.photobucket.com/albums/f333/jpiner/IMG_3960_zpsr1pbtuu3.jpg
Checking the output from the load cell while pressing with my thumb produced around a 6 mV change from the no load output of 60 mV. So I would expect a voltage change from the amp of ~3V with the default 100 ohm gain resistors. I checked the output of the AD8426 for both channels and the output stayed constant with varying force on the load cell. I also tried it on channel 2 and there was no change in voltage. Likewise the output from A0 and A1 remain constant when pressure is applied. I also varied the reference voltage for both channels and the results were the same.

Thanks,
John

Hi,

Can you try the testing procedure in the attached document and let us know how it goes.
RB-Onl-38ABE-01-Testprocedure.pdf (1.13 MB)

Step 6

First Test, Strain 1

Raw ADC Value (no Jumper): 325

Raw ADC Value (with Jumper): 656

Step 7

Second Test, Strain 1

Raw ADC Value (no Jumper): 325

Raw ADC Value (with Jumper): 325 (no change)

Step 8

First Test, Strain 2

Raw ADC Value (no Jumper): 336

Raw ADC Value (with Jumper): 656

**Step 9
**
Second Test, Strain 2

Raw ADC Value (no Jumper): 336

Raw ADC Value (with Jumper): 336 (no change)

Failed steps 7 and 9

Hi,

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