| 摘要 |
1,058,392. Resistance testing. ETABUSSEMENTS DAVEY BICKFORD SMITH & CIE SOC. ANON. FRANCAISE and F. URBAN. April 21, 1964 [April 30, 1963], No. 16479/64. Heading G1U. A resistance measuring device Fig. 1 (not shown), comprises a switchable D.C. supply connected over a series resistance to series assisting stabilizing diodes, to energize a reference resistor and an unknown resistor in series with a calibrated potentiometer therebetween; the potentiometer slider being connected to the base of a transistor whose emitter is returned through a calibrating variable resistor and whose collector is energized over a load resistor, in parallel with a Zener diode and series relay to operate at a preset voltage; the value of the unknown resistance being determined by the specific potentiometer setting necessary for relay operation. A modified resistance testing device (Fig. 2) comprises a reference resistor R 1 , in series with a variable resistor R x , which may be a shot firing circuit. Variable potentiometers are shunted across R 1 , R x and the sliders are connected to the bases of transistors T 1 , T 2 whose emitters are returned respectively to the junction of R 1 , R 1 and the lower end of R 1 . The collector circuits each contain a resistor shunted by a relay Z 1 or Z 2 in series with a Zener diode, and the transistor bases are biased to predetermined levels set by the potentiometer sliders. It is shown that relay Z 1 will operate when R x exceeds a critical value r 1 and that Z 2 will operate when it is in defect of a critical value r 2 to produce corresponding signal indications. The relays may be replaced by transformer coupled neon lamps. The testing device may be operatively assembled with a shot firing unit connected so that no shot may be fired if the firing circuit resistance lies outside a predetermined range of values. |
