So what you want me to do is, RDG.CNF>RD.SC.OF>Enable>2C D.int>ONLINE and put the two weights in and calibrate the two load cells separately?

Yes, you got it. The early DP41 meters were just two point Scale & Offset but the newer ones I believe scaling Multi Point which is nice. Depending on the DP (Decimal Point) placement and digits displayed you should get close in the readings. Within a few counts anyway. The DP 41 is a really nice meter but learning to program and set them up takes some time (and I recall plenty of frustration). You should hit within a few counts.

Ron

 

Yes, you got it. The early DP41 meters were just two point Scale & Offset but the newer ones I believe scaling Multi Point which is nice. Depending on the DP (Decimal Point) placement and digits displayed you should get close in the readings. Within a few counts anyway. The DP 41 is a really nice meter but learning to program and set them up takes some time (and I recall plenty of frustration). You should hit within a few counts.

Ron

Hi Ron, yeah I might be able to calibrate the two load cells separately. Since I'm using two load cells in my system, would it give me a constant reading wherever along the base plate I keep the mass ?

 

Yes, that should work just fine and the meters should display within a few counts. They should not only agree but be accurate as to their displayed data. Over the years Omega has actually improved the DP 41 meters. They were great for process display and control. I also liked the many option cards which could be added. Anyway yes, calibrate them individually using the same applied weight.

Ron

 

Yes, that should work just fine and the meters should display within a few counts. They should not only agree but be accurate as to their displayed data. Over the years Omega has actually improved the DP 41 meters. They were great for process display and control. I also liked the many option cards which could be added. Anyway yes, calibrate them individually using the same applied weight.

Ron

Then I should simply add these two meter readings?

 

hi A.
IMO using two DP41 is unnecessary, parallel the two L/C's into one DP41, then you will not have keep mentally adding the two DP41 readings.
Obviously you would carry out a calibration check using known weights.

May I ask why you have designed the suspended cross beam method for weighing, using two L/C's, when one overhead hanging L/C would be simpler and cheaper.?

What is the product you are weighing and to what accuracy.?

E

EDIT:
This is the type of hanging cell I had in mind.
https://www.amazon.co.uk/dp/B06XWST...3212833&sr=8-20&keywords=hanging+weight+scale

 

hi A.
IMO using two DP41 is unnecessary, parallel the two L/C's into one DP41, then you will not have keep mentally adding the two DP41 readings.
Obviously you would carry out a calibration check using known weights.

May I ask why you have designed the suspended cross beam method for weighing, using two L/C's, when one overhead hanging L/C would be simpler and cheaper.?

What is the product you are weighing and to what accuracy.?

E

This is actually a research project, E. A pseudo 2-D box will be suspended by these load cells. In the box a packing (2-25mm particles) will be filled. a liquid will be introduced to the packing and the holdup of the liquid will be measured. Using only 1 load cell makes the design a bit prone to failure (thats what I thought) hence went for two. Expected accuracy will be for atleast 100g.

 

This is actually a research project, E. A pseudo 2-D box will be suspended by these load cells. In the box a packing (2-25mm particles) will be filled. a liquid will be introduced to the packing and the holdup of the liquid will be measured. Using only 1 load cell makes the design a bit prone to failure (thats what I thought) hence went for two. Expected accuracy will be for atleast 100g.

What is a "pseudo 2-D box"????

Why would using only 1 load cell make the design more prone to failure? With one load cell, if the load cell fails the system fails. With two load cells, if either load cell fails the system fails. Which is more likely, one load cell failing? Or one of two load cells failing?

 

Then I should simply add these two meter readings?

No, if you setup (using READING SCALE & OFFSET 2-COORDINATE FORMAT MENU) found on page 53 you are setting each meter to read its own corresponding load cell. Now I may be reading into this wrong but I see each load cell measuring the same weight. as in working in parallel but not actually connected in parallel. I see each load cell and meter as an independent system.

If you have the actual weight to calibrate the load cells I would use the ON.L INE method verse MANUAL method. That will get you to the:
"INPUt 1", Input 1 ’s value
"REAd 1", Read 1 ’s value (with no weight you would enter 000000)
"INPUt 2", Input 2 ’s value
"REAd 2", Read 2 ’s value (you would enter the actual weight applied)
This is just using the 2 Coordinate Format and should be all you need.

With each meter individually calibrated they should read close to the same. I say close and not identical because some minor error is normal.

Ron

 

hi Ron,
As I understand Ashane wants to be able to place the weight at any point along the Base beam, perhaps he can clarify that point.?

The initial sketch shows a beam suspended by what I assume to be non stiff supports.
E

 

hi Ron,
As I understand Ashane wants to be able to place the weight at any point along the Base beam, perhaps he can clarify that point.?

The initial sketch shows a beam suspended by what I assume to be non stiff supports.
E

Hi Eric

Yes, I am not sure exactly what is going on. Hopefully Ashane will simplify this so even I "get it". I am not sure if it is just two redundant systems or where this is going.

Ron

 

Hey guys,

Thanks for everything. Let me explain. When I put the weight on the base plate depending on the place where i keep it the panel meter gives me different values. So in the case if I place a 5kg disc on the base plate it gives me different values.

The glass box on the picture is the which will be on top of this base plate and it will be filled with particles (about 80 kg). A fluid will be introduced and the fluid retention within this particles will be measured. For that I need a perfect calibration of the load cells.

 

hi Ashane,
As WB and I have said, using two load cells on that beam will give a different weight depending upon the position of the load on the beam.
I assume you do not wish to modify the metal box framework.?
How accurate do you want the weight readings, as the max load is 80kg.?

It would not take to much time to wire the two load cells in parallel to one indicator and carry out a calibration check, placing the calibration weights in different positions on the beam. The results should give you a confidence level in the systems accuracy/repeatability.
From this result you could make a decision on how to proceed.

Let us know what you find/decide, so that we can make further suggestions.

E

 

Hi E,

Yes, I do not wish to modify the metal framework. I would like to have an accuracy around 10 g.

Will try out yours and Ron's methods tomorrow and let you both know.

 

As WB and I have said, using two load cells on that beam will give a different weight depending upon the position of the load on the beam.

Ah, now I get it. Unless the applied weight is dead center of the beam I would expect to see different weights displayed. If the beam is removed and each unit setup separately they each will be accurate and display accurately what they sense. The only time they should agree with the beam in place is when the weight is centered on the beam. I see what you are seeing as normal. Also once the beam is in place, after setting up each unit individually the weight of the beam on each must be tared out.

Ron

 

Hi E,

Yes, I do not wish to modify the metal framework. I would like to have an accuracy around 10 g.

Will try out yours and Ron's methods tomorrow and let you both know.

Earlier you said 100 g. Now it's 10 g. At 80 kg that means you are asking for an accuracy of 1 part in 8000, which is 13 bits of accuracy. For perspective, 80 kg is about 175 lb, or the average weight of an adult male. 10 g is about the weight of two Hershey's kisses or about half a standard size Reese's peanut butter cup. So you are asking that your system be able to tell the difference between someone before and after they've had bit of a Reese's cup.

I'm a bit skeptical that you can take two load cells (of the same make and model) out of the box and hook them in parallel and get that kind of performance.

 

I'm a bit skeptical that you can take two load cells (of the same make and model) out of the box and hook them in parallel and get that kind of performance.

I have to agree with this. Starting with the actual load cell, Stainless steel "S" beam load cell with ±100 kgF range is not a bad cell but the allowable error needs to be considered.
SPECIFICATIONS
Excitation: 10 Vdc, 15 Vdc max
Output: 3 mV/V ±0.0075 mV/V
Linearity: ±0.03% FSO (0.1% 40 K)
Hysteresis: ±0.02% FSO (0.1% 40 K)
Repeatability: ±0.01% FSO (0.05% 40 K)
Zero Balance: ±1% FSO
Operating Temp Range: -40 to 93°C (-40 to 200°F)
Compensated Temp Range: 17 to 71°C (60 to 160°F)
Thermal Effects:
Zero: 0.002% FSO/°C
Span: 0.002% FSO/°C
Safe Overload: 150% of capacity
Ultimate Overload: 300% of capacity
Input Resistance: 350 ±10 Ω
Output Resistance: 350 ±10 Ω
Full Scale Deflection: 0.25 to 0.51 mm (0.010 to 0.020")
Construction: 17-4 PH stainless steel
Electrical (LC101/LCM101): 4-Conductor Shielded Cable
<100 kgf/250 lb: 9 m (30') 24 AWG
250 to 1000 kgf/250 to 2000 lb: 9 m (30') 20 AWG
≥1500 kgf/3000 lb: 4.5 m (15') 20 AWG
Mating Connector (LC111/LCM111):
≤100 kgf/200 lb: PT06F8-4S, sold separately
≥250 kgf/250 lb: PT06F10-6S, sold separately

Then we have the DP 41B Universal Meter at a glance:

• Universal Inputs: DC Voltage/Current, T/C, RTD, Strain
• Accuracy: ±0.005% rdg
• 6-Digit Color Changing LED Display
• Up to 142 Readings Per Second
• 10-Point Linearization
• 4 Isolated Open-Collector Output
• Isolated Analog Output, Optional
• Four Relays, Optional
• Ethernet or RS232/RS485, Optional
• NEMA 4 (IP65) Front Bezel
• Ratiometic Mode for Strain Gages

The allowable errors need to be algebraically added together. Then it looked like a cast weight set you were using for calibration / verification. The average slotted weight set made of cast is normally what I call a Class F set. Looking at 100 Kg I think about 10 grams. I may be wrong on that but I am sure you see where it is going.

I always had a weakness for Hershey's Kisses and Reese's Cups too.

Ron

 

Earlier you said 100 g. Now it's 10 g. At 80 kg that means you are asking for an accuracy of 1 part in 8000, which is 13 bits of accuracy. For perspective, 80 kg is about 175 lb, or the average weight of an adult male. 10 g is about the weight of two Hershey's kisses or about half a standard size Reese's peanut butter cup. So you are asking that your system be able to tell the difference between someone before and after they've had bit of a Reese's cup.

I'm a bit skeptical that you can take two load cells (of the same make and model) out of the box and hook them in parallel and get that kind of performance.

nice example.. Sorry about that number (10 g). Has to be around 100 g. But I should try to get it as accurate as possible. This thread is getting interesting.
Will try out the centering of the mass and the paralleling. Thanks guys. I shall let you know.

 

I'm a bit skeptical that you can take two load cells (of the same make and model) out of the box and hook them in parallel and get that kind of performance.

hi Ashane,
WB beat me too it, never going to get that accuracy on a 80kg scale, +/-0.1kg is achievable with that set up.
What is the actual load rating of each cell.??

As you have no proven data for how your weighing system is going to perform, you need to get some empirical data by carrying out the calibration checks as per my post #32.

Once you have this data you can make a decision on how to proceed.

E

 

hi Ashane,
WB beat me too it, never going to get that accuracy on a 80kg scale, +/-0.1kg is achievable with that set up.
What is the actual load rating of each cell.??

As you have no proven data for how your weighing system is going to perform, you need to get some empirical data by carrying out the calibration checks as per my post #32.

Once you have this data you can make a decision on how to proceed.

E

Hi E,

I just tried to do the parallel LC and get the values. Depending on the place it gives me a different value. Therefore, cannot confirm the weight is 5kg. Not as what we initially thought. Now im gonna look into Ron's method.

 

hi A,
If that is happening, ie: positioning changes weight, then there is a problem with the basic construction of that box/beam framework and/or the way it is assembled.

E