水柱の電気抵抗を利用したさく岩機ピストンストローク測定法について

抄録

There are several instances where electrical resistance of a carbon bar or a coiled wire is applied for measuring piston stroke of the rock-drill. It is considered in these, however, that the manufacture of an apparatus with these things is not simple, and that troubles by frictional force of the sliding piece, wear of it, variation of contact resistance and increase of resistance by sliding frictional heat will present themselves.
Now, the present writers applied electrical resistance of a water column and there were no troubles as above mentioned. As for the water, usual drinking water is found to be good, still more sensibility of measurement being increased with distilled water.
Amplifying is done as follows: bias voltage of an amplifier valve varies according to-notion of a moving pole bar in water, connected to the piston, therefore plate current varies.
This current is recorded by an oscilograph. By this, sensibility about 0.01mA/cm of current in water is amplified to about lmA/cm, and straightness of a calibration curve is very good.
Temperature rise of water is not found and diameter of the moving pole bar may be fi ner (2mm) than in another cases, for fluid resistance to this pole very small.