.
Hi Sarah,
You are correct, his drawing is Wrong in showing the power supply connections.

Others posting about PChannel FET's is not related to the TS's problem, the TS has the supplies reversed,
E

The drawing was wrong, you are correct as according your drawing it should be between +4.5 and -1.5 not -4.5 and +1.5. Anyway, I still get the same exact value.

 

Any signal can be represented as the superposition of a spectrum of sinusoidal waveforms of different amplitudes and frequencies from zero hertz to infinite hertz. The only way for there to be NO energy at ANY frequency other than 0 Hz (also known as "DC") is if the signal has existed since the beginning of time, has never changed, and will never change until the end of time. ANY signal that has ever or will ever undergo any change, has non-zero content at non-zero frequencies.

Look into Fourier series for more information.

If one second is fine, then you don't need much bandwidth (again, a few hertz), so you shouldn't be impeded too much by gain-bandwidth products.

Thanks for your illustration, I got it.

 

hi MMM.
You will find in most simple Load Cell systems there will be a little bounce in the reading, when the load is applied to the Load cell, it then it should settle to a steady value.
How have you got the LCell mounted.
Also, did you correct the power rail connection error.?

E

 

View attachment 282600

The drawing was wrong, you are correct as according your drawing it should be between +4.5 and -1.5 not -4.5 and +1.5. Anyway, I still get the same exact value.

Thanks everyone, I thought I was correct the first time! Of course, the real problem is that the older TL082 opamps only start to work properly with + and - 5V supplies, re: the TI datasheet.

 

hi MMM,
The simplest solution for using those 'old' OPA's would be to get a second 6V battery pack, so+/-6V supply.

E

 

hi MMM.
You will find in most simple Load Cell systems there will be a little bounce in the reading, when the load is applied to the Load cell, it then it should settle to a steady value.
How have you got the LCell mounted.
Also, did you correct the power rail connection error.?

E

What is the power rail connection error?

 

hi MMM,
The simplest solution for using those 'old' OPA's would be to get a second 6V battery pack, so+/-6V supply.

E

Ok, that's why I can use AD623AN instead as in post #45, but I should use another OpAmp cascaded with that one because the AD623AN cannot have a gain of 2000.

 

hi MMM
I use the AD623 in many weighing projects , why do you need a gain of 2000.

For a 5mV signal to 2V is only 400.
E

 

hi MMM
I use the AD623 in many weighing projects , why do you need a gain of 2000.

For a 5mV signal to 2V is only 400.
E

Yes, you're correct, I have repeated my calculations. Based on that I need a gain of 944 to amplify the maximum signal (5.3 mV in my case), and 944 is less than 1000 so theoretically this can be achieved by the AD623, I do not know if it is achievable practically or not (I don't have much experience in this). So, please give me a feedback on the following circuit:



I don't know how to get a 106.3 ohm in real life, but I think that the 100 ohm resistor with a 5 ohm resistor (considering the tolerance) will be very close to that value

 

hi MMM
Look at this option.
E

@MMM**MMM
If you need to set the Gain precisely, I use a 27R fixed resistor in series with a, 100R, 20 turn Cermet trim pot for Rg.
Remember the Load Cell is 1.2mV.V +/_0.1mV, so Rg may need to be adjustable.

 

hi MMM,
For a single supply, these two clips apply for the AD623.
E

 

hi MMM
Look at this option.
E

View attachment 282608

Hi, thanks for your contribution. I just want to understand why you placed C1, C2, and R5

 

hi,
It is recommended that you add some simple electrical filter to the inputs.
Look at this clip from the d/s
E

Added: @MMM**MMM
R5 a 10k is the value stated by the datasheet in order to meet the lowest Vout level.

 

You need to connect power to UB5

 

I did mention this on post #13.

 

You need to connect power to UB5

View attachment 282614

It is already connected, as U5B is the second channel of U5. The software I am using is multisim, and it does so to minimize duplication (or redundant connections) unlike ltspice

 

To be certain, why not try another device U7A?

 

It is already connected, as U5B is the second channel of U5. The software I am using is multisim, and it does so to minimize duplication (or redundant connections) unlike ltspice

It depends on the simulator. Try it to be sure. It's called troubleshooting. The example libraries in TINA all have all power pins connected.

 

It depends on the simulator. Try it to be sure. It's called troubleshooting. The example libraries in TINA all have all power pins connected.

Thanks for your note I will do so

 

To be certain, why not try another device U7A?

Can you suggest another one?