Is there an instrument for testing alcohol concentration?

Yes, it's called alcohol

hydrometer

. When using it, first pour alcohol into a

measuring cylinder, put the hydrometer in, and it will float. Read the

scale

value of the liquid level on the alcohol meter and measure the alcohol temperature, because the scale value is marked according to the value of 2℃, so compare with the attached table. The

measuring range

of the alcohol meter is different, so you should choose it according to your needs. If you do experiments, this accuracy

degree

is enough.