| 摘要 |
751,973. Resistance measurement. RECORD ELECTRICAL CO., Ltd., and SPAINK, P. F. ABBINK-. Dec. 15, 1954 [Feb. 2, 1954], No. 3041/54. Addition to 679,511. Class 37. An instrument for measuring electrical resistance of the kind described in Specification 679,511 wherein a variable-speed A.C. generator whose output voltage is proportional to fre. quency is connected in a primary circuit in series with a choke presenting at the normal working frequency an impedance exceeding that of the load whereby the generator current is stabilized for all speeds above a fixed minimum, is provided with a secondary circuit comprising a rectifier milliammeter in series with a swamp resistance and a second choke, and a coupling element comprising a further resistance interconnecting the primary and secondary circuits, across which is connected the unknown resistance to be measured, whereby the meter measures the voltage appearing across the further resistance as a function of the unknown resistance. In Fig. 1 a hand generator A energizes the primary of transformer T in series with choke L1 and the secondary shunted by resistance R1 energizes rectifier milliammeter M in series with choke L2 and resistance R2 to measure the voltage developed across R1 as a function of the unknown resistance connectible between terminals XX across the transformer primary. Proportionality is variable by adjusting the secondary circuit impedance or the transformer ratio. In a modification (Fig. 2, not shown) the unknown resistance is connectible across a third winding of the transformer, and it may also be connected across the secondary thereof. Fig. 3 shows a modification dispensing with the transformer wherein the generator A in series with the choke L1 energizes resistance R1 across which is connected the unknown resistance and the series circuit comprising choke L2, rectifier milliammeter M and rechoke L2, rectifier milliammeter M and resistance R2. |
