| 摘要 |
995,922. Measuring resistivity. SIEMENSSCHUCKERTWERKE A.G. Oct. 1, 1962 [Sept. 30, 1961], No. 37202/62. Heading G1U. In a method for measuring the resistivity of material in a rod 1, current is passed along the rod and through a resistor 4 and an instrument 18 measures the voltage between two points on the rod spaced a given distance apart. The diameter of the rod is measured, so as to provide information for adjusting an arrangement 6, whereby a voltage is set up which bears a prefixed proportionality to the square root of the cross-sectional area of the rod. This voltage is fed to a device 17 which adjusts the value of the current passed along the rod and through the resistor 4 to make the voltage drop across the resistor 4 equal to the voltage set up in the arrangement 6. This arrangement ensures that the same constant current density is applied to all rods under test so that each resistivity may be read off directly from the meter. The arrangement for passing current along the rod includes a triode 3 with the resistor 4 in its cathode circuit and the rod under test in its anode. A variable gain amplifier 17 controls the grid voltage of the triode in response to the difference between the voltage across the resistor 4 and that across a potentiometer 6 set up in accordance with the measured cross sectional area of the rod, so that a current adjusted to be of constant density is provided. The rod may be of a semi-conductor material, e.g. monocrystalline silicon. |
