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[Reply #15 on:]

Values given may be increased without limit."
So it's better 1.0 mF ceramic or 25 mF electolytic?

It looks like the 25 mF electrolytic since you can't get the 1.0 mF tantalum and it says bigger is better for electrolytic.

I've changed to 1 Amp devices, and i'll use raw pin on arduino pro mini (3v3 ver.). It'll be ok?

I think the answer is yes, but you would be safer posting your revised schematics to make sure there are no misunderstandings.

[Reply #16 on:]

I found all capacitor in tantalum but not the 1.0 mF

odd that is the single most common value. The recomended values are only a minimum you can use more if you want.

[Reply #17 on:]

You don't need the -5V supply at all. The INA122 will work down to 2.2V total supply voltage and its common mode input voltage includes ground. So ditch the 79L05 and connect pin 4 of the INA122 to ground instead. See Fig 5 on the datasheet.

Consider the situation where the unbalanced state of the bridge, Vunb, is <= 0.1V/G, where G is the gain of the instrumentation amp. While the common mode input voltage includes ground, the output voltage of the instrumentation amplifier when operated from a single supply does not.

The OP's original plan takes that into consideration.

That's a valid point. However, if a resistor of around 5K to 10K is connected between the amplifier output and ground, then the output voltage range will probably go right down to ground, unless the amplifier output stage is of an unusual design.

[Reply #18 on:]

You don't need the -5V supply at all. The INA122 will work down to 2.2V total supply voltage and its common mode input voltage includes ground. So ditch the 79L05 and connect pin 4 of the INA122 to ground instead. See Fig 5 on the datasheet.

Consider the situation where the unbalanced state of the bridge, Vunb, is <= 0.1V/G, where G is the gain of the instrumentation amp. While the common mode input voltage includes ground, the output voltage of the instrumentation amplifier when operated from a single supply does not.

The OP's original plan takes that into consideration.

That's a valid point. However, if a resistor of around 5K to 10K is connected between the amplifier output and ground, then the output voltage range will probably go right down to ground, unless the amplifier output stage is of an unusual design.

It is of an unusual design. Figure 5 shows what to expect with a ground referenced single supply and what to do about it.