Load Cell

[Laia]

Dear all,

I am new here, I want to know what exactly I need for connect a Honeyweel Load Cell model 31. Can someone help me?

Thank you very much,

Laia

[johnsold]

Laia,

What do you want to connect it to? 

Assuming that you are talking about connectng it to a computer, you will need, at minimum:

1. A power source to excite the load cell.  The voltage and current requirements vary depending on the model of the load cell.

2. An amplifier or signal conditioner, which may be separate or combined with:

3. A Data Acquisition device which can perform analog to digital conversion at a resolution and rate which is suitable for your application (again, dependent on the specific load cell model).

4. A physical connection and driver software between the computer and the Data Acquisition device.

5. Application software, such as LabVIEW, to process the data acquired.

Lynn

[Laia]

Thank you very much for your replay.

We have another question about the process, now we have to choose which load cell fits better. If we want a precision of 0.01 g., the capacity of the load cell is 1000 g, with an excitation of 5V, and a tolerance of 1.5 mV/V. How can we know if the load cell is going to display a precision of 0.01g?

Thank you very much,

Laia 

[Henrik_Volkers]

> If we want a precision of 0.01 g., the capacity of the load cell is 1000 g

Get a lab grade balance!

Well, 10ppm is not impossible but the rest of the setup is usually the limiting factor. Can you handle all the temperature drifts? Material creeping?

Good bridge amplifier are close to the theoretical limit (resistive noise of the bridge)  .. however your requirement sound very academic 😉

> How can we know if the load cell is going to display a precision of 0.01g?

Calibration and a honest uncertaincy budged ...

[johnsold]

I agree with Henrik.  You are pushing the limits for a very carefully designed system, and from the nature of your post, I doubt that you will have much chance of success.

Let's take a big step back.  Start with the fundamentals.  What are you trying to measure? What are you going to do with the measurements after you make them? You want 10 mg precision on measurements up to 1 kg, right? How fast do you need to make the measurements? What is the accuracy requirement (accuracy and precision are not the same thing)?  Is the system stable enough for 10 ppm to make sense?

Lynn

[Laia]

Thank you for all,

The project consists of burning a methane clathrate sample. We would like to take data of the melting water and also of the weight of the sample. We need a precision of 0.01g, and we want to get 20 measurements in 1 second. We need a load cell with a capacity of 250 gr. and the other one 700 gr. Should be possible?

Thank you,

Laia

[johnsold]

Laia,

As Henrik suggested earlier, you should look at laboratory balances.  You can find a several devices with capacity of 800 g to ~2 kg and readability to 10 mg or less.  RS-232 interfaces are available.  Reading rates of 10 to 20+ readings per second are about as fast as these devices seem to go. The first reading (dependent on settling time) may be a few seconds.  I looked at Sartorius and Metler-Toledo.  There are other companies as well.  You will need to look carefully at not only the basic specifications but also the communications capability.

When you have narrowed your choices down to a few models which you think might work, talk to the sales representatives and ask very specific questions about how fast you can read the data and how fast the weights can change before the "unstable" detectors inside the devices cut off your readings.

What you are asking looks like it is near the limit of many of these devices. When pushing equipment close to the limits, be very careful that you do not buy something which later turns out to be not quite good enough.  You might even consider renting a balance to make sure you can get it to do what you want before you commit to a purchase.

Lynn

[beanbag]

---

@johnsold wrote:

 and from the nature of your post, I doubt that you will have much chance of success.

---

Ouch, LOL.

The load cell you are looking at has a sensitivity of 7.5mv per 1000g if you drive it with 5v, or 75 nV resolution required to meansure 10mg.  It may be possible to measure this with an instrumentation amplifier like the AD8429, but you have to be pretty careful on the elctronics side.

Another suggestion is to buy a load cell that is a much smaller value, say 50g, and build a mechanical counterbalance.

[Luca85]

hi all

I would need to undestand if this type of load cell (Honeyweel Load Cell model 31) is working with a piezoelectic principle

thank you very much

best regards 

Luca

[johnsold]

Luca,

You are asking an unrelated question (except for the part number) on a 4year-old thread.  It is generally better to start a new thread and link to the old one if relevant.

The information you want is found in the data sheet on pages 1 and 2.

Lynn