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How to connect this strain gauge?

kusspuss

Aug 25, 2023
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recently i bought this strain guage where vender said it is 4bridge, i am not sure how to connect this with power suppl so that this strain gauge operate safe the resistance of bridge is 120ohm strain gauge.
please need guide thank you.
 

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danadak

Feb 19, 2021
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Its a full bridge strain gauge, so power goes to Red and Black,
Green and White to A/D or IA input.

The lower R valued ones may need a R in series with power connection
to limit current, which creates a CM Voltage so A/D has to be differential
input, or use IA. Does information describe current limit allowed, max ?


Regards, Dana.
 

kusspuss

Aug 25, 2023
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Its a full bridge strain gauge, so power goes to Red and Black,
Green and White to A/D or IA input.

The lower R valued ones may need a R in series with power connection
to limit current, which creates a CM Voltage so A/D has to be differential
input, or use IA. Does information describe current limit allowed, max ?


Regards, Dana.
yes i have AD620 module too amplify it , the vender told me 25mA.how much safe power supply should give and how can i connect this with breadboard

Edit: do i need voltage divider , i have voltage regular 3-24V DC

thankyou very much
 
Last edited:

danadak

Feb 19, 2021
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What A/D are you going to use to read the output of AD620 ?
In other words what is the desired output range you want out
of the AD620 ?

Will you be feeding the AD620 output to an A/D, if so whats is
its input range allowed ?



Regards, Dana.
 

kusspuss

Aug 25, 2023
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What A/D are you going to use to read the output of AD620 ?
In other words what is the desired output range you want out
of the AD620 ?

Will you be feeding the AD620 output to an A/D, if so whats is
its input range allowed ?



Regards, Dana.
the mv voltage from AD620will be feed into Arduino , the voltage allowed output from AD620 is 9V .
 

danadak

Feb 19, 2021
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Tha allowed Arduino input range is 0 - Vcc, Vcc is either 3.3 or 5V.

So you cannot overdrive the input. Circuits you can use to accomplish this :


The Ad620 has to be operated at higher V than Arduino Vcc if you want maximum range, becuse its limited,
not rail to rail :

1693064567700.png



Regards, Dana.
 

kusspuss

Aug 25, 2023
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Tha allowed Arduino input range is 0 - Vcc, Vcc is either 3.3 or 5V.

So you cannot overdrive the input. Circuits you can use to accomplish this :


The Ad620 has to be operated at higher V than Arduino Vcc if you want maximum range, becuse its limited,
not rail to rail :

View attachment 60410



Regards, Dana.
if i supply 3-5 V to AD620 , will it will be enough ? secondly i want to know that how can i suppl power to 4 strain gauge full bridge if wheatstone bridge not required
 

bertus

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Nov 8, 2019
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Hello,

The AD620 works from +/- 2.3 AKA 4.6 Volts;
AD620_power.png
This is the gauge circuit from the datasheet:
AD620_pressure_gauge.png
Bertus
 

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danadak

Feb 19, 2021
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The gauge circuit is driving the ground, in this case, of the Arduino which would
pose additional problems interfacing to it.

You have a bridge, connected to Vcc, lets say 5V. Its CM V is 2.5V. Its deviation
you have to compute, but for this example, when bridge unbalanced ranges
+/- 100 mV. So its output ranges from 2.6V to 2.4V.

Your arduino, says its running off 5V, the A/D input range is 0 - 5V.

So you have to translate 2.4V to 2.6 V to 0 V to 5.0 V. So start with G needed.
G = 5V / .2V = 25. So that gives you the slope of Vout / Vin.

Now you have to offset that by the CM voltage of 2.5 V so you get 0 - 5 V.
The easy way is to have a - supply as well on AD620 and use a OpAmp
differential circuit to subtract out the offset. A tool you can play with :


A design method for offset OpAmp is :


Of course you dont have to use the entire range of Arduino A/D, you can
trade that off for other considerations.

For negative supply you can use PWM output of Arduino and this :


1693069608765.png

Because the AD620 has excellent PSRR that should be OK, but doing an error buget or
sim always prudent.



Regards, Dana.
 
Last edited:

bertus

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Hello,

The 10 Volts limit is set by the ICL7660.
It could be lower as 3.5 Volts, The LM358 works from +/- 1.5 Volts, The AD620 from +/- 2.3 Volts.
The board should be able to handle 2.3 to 10 Volts.

Bertus
 

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danadak

Feb 19, 2021
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1693071055709.png

Sim for -V generator, you will have to juggle values to get AD620 output
swing down to 0V (to maximize Arduino A/D input range). Also use Schottky
diodes versus the Si I used, to get more - V. Basically strive for
~ 2V so that AD620 can swing to ground. Note using Schottky's versus IN914
should get closer to -2V needed.

I ran Arduino PWM at 1 Khz.....to drive this neg V generator.



Regards, Dana.
 
Last edited:

kusspuss

Aug 25, 2023
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Hello,

The 10 Volts limit is set by the ICL7660.
It could be lower as 3.5 Volts, The LM358 works from +/- 1.5 Volts, The AD620 from +/- 2.3 Volts.
The board should be able to handle 2.3 to 10 Volts.

Bertus
for this Fully strain gauge bridge how can i power it up , there are four terminals , two terminal S+ and S- go to AD620 signal + and signal -
 

kusspuss

Aug 25, 2023
32
Joined
Aug 25, 2023
Messages
32
The gauge circuit is driving the ground, in this case, of the Arduino which would
pose additional problems interfacing to it.

You have a bridge, connected to Vcc, lets say 5V. Its CM V is 2.5V. Its deviation
you have to compute, but for this example, when bridge unbalanced ranges
+/- 100 mV. So its output ranges from 2.6V to 2.4V.

Your arduino, says its running off 5V, the A/D input range is 0 - 5V.

So you have to translate 2.4V to 2.6 V to 0 V to 5.0 V. So start with G needed.
G = 5V / .2V = 25. So that gives you the slope of Vout / Vin.

Now you have to offset that by the CM voltage of 2.5 V so you get 0 - 5 V.
The easy way is to have a - supply as well on AD620 and use a OpAmp
differential circuit to subtract out the offset. A tool you can play with :


A design method for offset OpAmp is :


Of course you dont have to use the entire range of Arduino A/D, you can
trade that off for other considerations.

For negative supply you can use PWM output of Arduino and this :


View attachment 60416

Because the AD620 has excellent PSRR that should be OK, but doing an error buget or
sim always prudent.



Regards, Dana.
i have question that the Module i have , do i need to make another OP and connect AD620 MOdule with it ?
 

bertus

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Nov 8, 2019
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Hello,

I have written the boards input names on your sensor picture:
SG1_comment.jpg

Do you have a datasheet of the gauge?
That way we can see the maximum exiting voltage of the gauge.

Bertus
 

kusspuss

Aug 25, 2023
32
Joined
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Hello,

I have written the boards input names on your sensor picture:
View attachment 60422

Do you have a datasheet of the gauge?
That way we can see the maximum exiting voltage of the gauge.

Bertus
the company said that , the working current during static measurement is about 25mA , unfortunately could not find datasheet
 
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