Improvements in compressed scale measuring instrument circuits

  • Inventors:
  • Assignees: Sangamo Weston
  • Publication Date: February 22, 1961
  • Publication Number: GB-861582-A


861,582. Measuring instruments. SANGAMO WESTON Ltd. June 14, 1957 [June 18, 1956], No. 18878/57. Class 37. A voltage - measuring instrument having a compressed scale for indicating voltage exceeding a certain level (Fig. 2, not shown) comprises a milliammeter 1 shunted by a series resistor 3 and a silicon rectifier diode in reverse polarity to a unidirectional voltage source 7 to be measured; the combined circuit being connected thereto over a series resistor 5. Up to a critical voltage (e.g. 10 volts), the rectifier has high impedance and the meter operates with resistor 5 as a high sensitivity voltmeter, while when the critical voltage is exceeded the rectifier breaks down to a low resistance in the reverse direction shunting the meter so that its voltage measuring sensitivity is reduced. In a modification (Fig. 3, not shown) the rectifier is shunted by a further resistor effective to increase the breakdown voltage of the diode and shunt the meter while the diode is non- conductive so that the compression of the upper part of the scale is also compressed (Fig. 4, not shown). A theoretical analysis is given. The value of resistor 3 is such that the highest reading of the lower scale range coincides with the lowest reading of the high range.




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Cited By (5)

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    JP-S4979280-UJuly 09, 1974
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    US-3247387-AApril 19, 1966Western Electric CoPhotoelectric bridge circuit with indicator compensated for non-linear input
    US-3268813-AAugust 23, 1966American Mach & FoundryMeter circuits with multiple increments of different slopes
    US-3614611-AOctober 19, 1971Fred BenjaminVoltage and wattage indicator for arc lamps