Is it possible for you to check this TINA circuit for me, where I am wrong and what should I change in the scheme?
Please can you show me any functional scheme to implement it in Load cell sensor together with strain gauge full bridge 350 ohm.
I have tried several Instrumentation Amplifiers but have had no success, and I think 2 INA333 or INA2333 might be more suitable for my project.4532.Noname.TSC
Hi Shkelqim,
If you require a circuit to amplify the differential signal from the load cell sensor, producing a differential output, you can easily implement the circuit using a dual op-amp such as the OPA2333. See the circuit at the bottom of the post. The gain of the amplifier stage is given by the ratio of the RFx and RG resistors:
Gain = 1 +2*(RF / RG)
The output common-mode voltage is the same as the input common-mode voltage. In this example, the output common-mode is centered at +2.5V (mid-supply). In the example below, the gain is set to 3-V/V. You can scale resistor RG per the circuit gain requirement. Choose the percent tolerance, and temperature drift spec of the RF and RG resistors per the gain error accuracy and gain error drift requirement. For example, when using 0.05% tolerance RF and RG tolerance resistors, the circuit provide a very worst gain error of ±0.1%.
Thank you and Regards,
Luis
Differential_output_OPA2333.TSC
Hi Shkelqim,
If I understood correctly, your bridge offers full-scale signal of +/- 20mV. The ADC for weight scales device you feature above, from another manufacturer, already integrates a programmable gain amplifier (PGA). According to your equation "+/- 0.5 ( AVDD / gain)" above, if AVDD = 4.3V, the ADC offers full-scale ranges +/-16.8mV, +/-33.5mV, 67.18mV for 32x, 64x, 128x gains respectively when AVDD=4.3V.
In general, this type of weight scale ADC connects directly into the load cell, and for example, you could use the lower gain 64x directly, accommodating the +/- 20mV bridge directly.
(Edit 9-13-23, corrected OPA2333 gain stage and ADC full-scale)
For example, using the OPA333 on Gain of 3.36x with RG=8.45k and RF1, RF2 =10k and then follow with the ADC device above set up on G=32x --ADC full -scale +/-67.18mV-- is possible.
TINA:
4276.OPA2333_differential2.TSC
By the way, Texas Instruments offers 24-bit ADCs for bridge sensors and weight scales such as ADS1232 and ADS1234:
See application note: "The ADS1232 and ADS1234: Complete Front End Solutions for Weigh Scales"
If you have interest on the ADS1232 or ADS1234, Kindly submit a query on the Data Converters Forum.
Thank you and Regards,
Luis
Thank you Luis,
As for your suggestion :If you have interest on the ADS1232 or ADS1234.
Yes sure i used before ADS1243 https://www.ti.com/lit/ds/symlink/ads1243.pdf?ts=1694710146991&ref_url=https%253A%252F%252Fwww.google.com%252F and i was the same problems with stability and interferences, but without
opa,
The biggest problems are the sensors, some types of sensors work and some other types don't work and have problems, the same story as the HX711 where simple sensors up to 50Kg work very well without problems and it amazes me how this thing is possible with such a low cost to work so well, and where you can't find a contact with the company, and there is no manual except the one published by Sparkfun. For this reason, I am also producing my sensors to go up to 250 Kg, and I am trying to create a board that works only with these sensors that I am creating, but I am facing the problems that I have described and I am asking for your help , because I got tired of noname products and I want to use only those produced by serious companies like TI, Renesas, Analog....
Anyway, thank you for your help.
