Using a S2M transducer to read force measurements. New to LabVIEW.

[Vin91]

Hey!

I am using an internal excitation with an excitation value of 2.5V. As you suggested, I have attached the VI with the modified values. The sample rate is 100. Thanks for the help!

Regards,

Vinayak

[GerdW]

Hi Vin,

I haven't used plain bridge-type sensors before, but have you tried to increase the scale amplification by a factor of 1000? I would try to set "first electrical value" to zero and "2nd electrical value" to 0.002…

(When reading hammer impacts you surely want to use a higher samplerate than just 100Hz.)

[Vin91]

Hey,

Ok I will try that. Yeah originally I was getting an error that I couldn't use a sample rate higher than 100 Hz, even in high speed mode. I am not sure if it will still give me that error.

So the electrical limits would be first value 0 for 0N and second value 0.002 for 20N? Because the sensor is rated for 2mv/V for 20N.

Regards,

Vin

[Vin91]

I am just using the hammer to test if the code is working. It will in application however read frictional forces over the course of a test and hence I think that 100Hz should probably be enough. The test would be conducted for maybe 30 mins to an hour. Let me know if this is ok.

Regards,

Vin

[cbutcher]

At least to me (and perhaps GerdW knows otherwise and better) your values look ok.

If you use your fingers to manipulate the sensor, do you see variation in the directions you expect?

Push it in one direction, then the other, and see if pushing harder produces a larger variation.

20N is ~2kg, if you hang a weight from your sensor - so you could do that to get a more quantitative measure.

Edit: on the topic of wiring, and looking at your datasheet (thank you for attaching) you'll want to connect your blue wire to EX+, black to EX-, white to HI and red to LO (where the capitalised values are the terms given in the NI datasheet).

If I'm taking a guess, the "sensing element" wires are to allow a 4-wire Kelvin wiring system, in which the EX+- wires carry the current to the bridge, and the voltage drop along the sensing wires is negligible, since they don't carry excitation current. I'm not certain why you'd need to know those values, except perhaps for verification of your excitation voltage?

[Vin91]

Hi no problem!! Thanks for the help. Yes I've checked the wirings as you mentioned and it seems to be right. I've manipulated the excitation values and the scales as GerdW suggested and it doesn't seem to affect my result. My only remaining conclusion is that the force transducer does not work. I've tried hanging a weight from the transducer and that doesn't seem to result in a big deviation. I'm getting a result like the picture attached. 

[cbutcher]

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@Vin91 wrote:

I'm getting a result like the picture attached. 

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I think the forum might have dropped your image...

If you can estimate the size of the variation, (or if we check the image) then you can try and assess if the sensor is broken (possible, but hopefully not the case) or if there's a scaling/LabVIEW-related problem (possibly easier, likely cheaper) to fix.

[Vin91]

Yeah I am not sure what happened to the image. I don't have access to the sensor till monday but I will add the picture and send it again on monday. Thanks for the help!

[Vin91]

Hey,

Sorry for the late response but I finally have access to the sensor. I have attached a couple of graphs but they show similar results. This seems to be the constant response from the sensor. Please let me know if you have any ideas.

[cbutcher]

Just to ask the obvious question, in your images it looks like ~3 minutes of data at ~8mV.

Was there something happening at the time with the sensor that makes you believe you'd see variation? (e.g. movement, hammer, whatever)