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Topic: Amplifying a 100 mv signal from a pressure transducer to 0-5V or 0-10V (Read 6049 times) previous topic - next topic

alitarraf

Hello everyone,

I am a beginner in arduino, and electronics in general.

I need to amplify a 100mv signal to 0-5V or 0-10V that I can read with my arduino.

I have come across a previous post addressing the same issue here:

http://forum.arduino.cc/index.php?topic=205229.0

But I am not quite sure about which op amp to use, an instrumentation amplifier, or an operational amplifier?

I attached the datasheet of the sensor.

Thank you
Ali T.

mart256

I need to amplify a 100mv signal to 0-5V or 0-10V that I can read with my arduino.

Arduino analog ports read 0-5V, so I would dismiss 0-10V.

alitarraf

Thanks for pointing that out.

I am open to any suggestions, even if it is to buy an off the shelf unit that will do the job.

My main concern is to minimize noise issues, and have a reasonable degree of accuracy.

Ali T.

Magician


alitarraf

I would like to have a minimum of 0.5-1Khz. I would like to use this sensor for static pressure measurement.
I am using other dynamic pressure sensors with Labview and specialized DAQ that can go up to 500Khz.

But if we can design the circuitry to be able to do 50Khz or 100Khz, that would be also great to have.

Thanks for asking.
Ali T.

Magician

Than INA125 is a way to go. Google data sheet.
 For lower sampl. rate I thought you may use HX711.

http://www.aliexpress.com/item/For-Arduino-Dual-channel-HX711-Weighing-Pressure-Sensor-24-bit-Precision-A-D-Module/32296409056.html?spm=2114.031010208.3.2.xXrvBw&ws_ab_test=201556_6,201527_3_71_72_73_74_75,0_0

 

Wawa

I think the HX711 is unsuitable because of the lower supply voltage (<5volt).

The sensor is rated for 10volt, so the INA125 with it's 10volt reference would be a good match.
Supply the INA with 12volt regulated, IAref to ground, and a 1:1 voltage divider on the output.
Leo..

Magician

I think the HX711 is unsuitable because of the lower supply voltage (<5volt).

The sensor is rated for 10volt, so the INA125 with it's 10volt reference would be a good match.
Supply the INA with 12volt regulated, IAref to ground, and a 1:1 voltage divider on the output.
Leo..
I find no indication that sensor has active components, probably it's just bridge 4- resistive strain gauges, same as load cell.
https://en.wikipedia.org/wiki/Strain_gauge

My understanding of "rated voltage" is the maximum voltage you may apply accounting dissipated power - accuracy loss due temperature change. Nothing prevents to apply low voltage, down to 1V or less.

alitarraf

The INA 125 seems suitable for a wide range of operation frequencies.

Is there any assembled circuit module for the INA 125, like the one available in the link "Magician" posted about the HX711 used for weighing scales?

If not, I will try to work out a circuit schematic with the INA 125 and have your feedback on it soon.

Thank you
Ali T.

Wawa

My understanding of "rated voltage" is the maximum voltage you may apply accounting dissipated power - accuracy loss due temperature change. Nothing prevents to apply low voltage, down to 1V or less.
That's what I also understand. The only thing that also will go down with supply voltage is output voltage.
I think the Sparkfun HX711 is set for 4.3volt bridge supply.
Sensor output will be 43mV max at that voltage.
That has to be weighed against the specs of the amplifier and A/D converters.
Leo..







raschemmel

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Magician

Quote
That's what I also understand. The only thing that also will go down with supply voltage is output voltage.
I think the Sparkfun HX711 is set for 4.3volt bridge supply.
Sensor output will be 43mV max at that voltage.
That has to be weighed against the specs of the amplifier and A/D converters.
I agree, that useful signal level diminishing with lower supply voltage.  But for low sampling rate , load cell needs only 1- 10 sps,  it's not an issue, as 24-bits adc brings 16384x  additional gain compare to arduino's 10-bits ADC. The problem may arise if required sampling rate > 1 msps, where high resolution ADC isn't accessible  or cost too much.
Author wants  1 ksps, so Hx711 is not an option, but I'd look at ADS1115

or AD7705

IMHO, external ADC with internal PGA is better option, than design INA125 board + 10V power supply interface like they did in 80-x or 90-x,  luckily price for such module is quite reasonable.


alitarraf

Guys,
I found this company who does an interesting board with the INA 125 and a butter-worth filter selling at around 40$ with shipping.

I am attaching the datasheet and a link to their website, please let me know your thoughts.

http://picom2.com/Phillips_Instruments.html

Thanks
Ali T.

Magician

In my opinion, board is obsolete.  You will have to design another interface stage between board(+-12V) and arduino(+5V).
Doesn't make sense.   I change my mind saying INA125 in the beginning (so INA122 - single supply 'd be better), to AD7705 or ADS1115 module, but external ADC brings better resolution, sooner or later you 'll realize that arduino's 10-bits is not enough

raschemmel

ADS1115

If you can spare the $15 it's worth it to have 16-bit resolution and programmable gain.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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