Null Offset LabVIEW Program

[RavensFan]

I disagree also.  Even the most simple application of a digital scale to measure your weight will continuously measure and display the load on it.  It doesn't rely on someone pressing a "weigh me now button".  Although the scale we have has a special feature that once it has sensed the weight as stabilized, it will freeze the display there for a few seconds so you can step off and read it better.

[JÞB]

OK, I've used it that way too!  And, in fact for measuring impact and vibration (as well as too determine how fast dishes dry)

I was

[billko]

How fast do dishes dry???

[JÞB]

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@billko wrote:

How fast do dishes dry???

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Apparently, it depends on the water hardness (Grains) Salinity, from softening, Etching from repeated wash cycles and the exact formulation of the rinse agent. (Temperarue, type of ware, material....) Someone would need to wash a lot of dishes a lot of times to perform that analysis. 😄

That's just an educated guess-I'm not the scientist that wrote the system requirements for the automation of that experiment set-up at an unnamed company

[pahlevi28]

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@cbutcher wrote:

Dear OP...

There are now disagreements over what you're trying to do... it seems like the following are your suggested options:

• Carry out a brief (~1s?) measurement to get a mean value, then use that as the tare for a continuous measurement afterwards. The tare in this case will not be updated, but will be taken at the beginning of the VI each time you run it. This is the approach that appeared to be suggested by your original example, and was followed by my suggestions and then crossrulz's suggestion (which implemented the fix I suggested)
• Carry out two fixed-length measurements, the first to get a zero value, then the second to make a measurement. This appears to be what JB (sorry, no attempts at your middle character, although I vaguely recall forum posts discussing how to appropriately insert it...) is suggesting. If you run the VI from another VI, this might be a better suggestion, because it will limit the time that this VI runs for. Advantage is that the "tare" value is close in time to the measurement value, and it's not possible to have an unexpectedly long run. Disadvantage: you can't easily view things if you're adding the weight 'interactively'...

RavensFan also pointed out a problem with your Mean usage - as he said, you should use the Mean.vi, not the PtByPt version (which accepts only a single point per call).

Can you clarify what you're looking for here, and suggest any further problems following the already posted advice?

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I'm sorry for late response in this few days.

Honestly, I need to acquire 8 channel input data. Which is there is summing operation.

ch 1 + ch 2 = F_x

ch 3 + ch 4 = Fy

ch 5 + ch 6 + ch 7 + ch 8 = Fz.

I've made a program for this case (vi attached). Would you guys mind to check my .vi file to make sure this 'tare function' to zero-ing the averaged value each summing operation?

Thank you.

[JÞB]

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@pahlevi28 wrote:

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@cbutcher wrote:

Dear OP...

There are now disagreements over what you're trying to do... it seems like the following are your suggested options:

• Carry out a brief (~1s?) measurement to get a mean value, then use that as the tare for a continuous measurement afterwards. The tare in this case will not be updated, but will be taken at the beginning of the VI each time you run it. This is the approach that appeared to be suggested by your original example, and was followed by my suggestions and then crossrulz's suggestion (which implemented the fix I suggested)
• Carry out two fixed-length measurements, the first to get a zero value, then the second to make a measurement. This appears to be what JB (sorry, no attempts at your middle character, although I vaguely recall forum posts discussing how to appropriately insert it...) is suggesting. If you run the VI from another VI, this might be a better suggestion, because it will limit the time that this VI runs for. Advantage is that the "tare" value is close in time to the measurement value, and it's not possible to have an unexpectedly long run. Disadvantage: you can't easily view things if you're adding the weight 'interactively'...

RavensFan also pointed out a problem with your Mean usage - as he said, you should use the Mean.vi, not the PtByPt version (which accepts only a single point per call).

Can you clarify what you're looking for here, and suggest any further problems following the already posted advice?

---

I'm sorry for late response in this few days.

Honestly, I need to acquire 8 channel input data. Which is there is summing operation.

ch 1 + ch 2 = F_x

ch 3 + ch 4 = Fy

ch 5 + ch 6 + ch 7 + ch 8 = Fz.

I've made a program for this case (vi attached). Would you guys mind to check my .vi file to make sure this 'tare function' to zero-ing the averaged value each summing operation?

Thank you.

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That looks very reasonable.  I would suspect the UX might be a little "Flakey" since the user must decide when no load is applied and Tare at that point (and woe to the user that presses start with a load applied) but the operation is correct