| 摘要 |
<p>PURPOSE:To selecta measurement range automatically at a high speed during the measurement of an AC voltmeter, etc., by judging an unknown input voltage on tree basis from a wide to a narrow range successively. CONSTITUTION:For example, when an input voltage is -46dB (5mV), it is amplified up to -16dB (158mV) and converted 21 into a direct current. The obtained DC voltage is 0.1-3.16V, and a window comparator 23 generates an output. Then, transistor TRs 28 and 40 turn on and an amplifier 3 generates a -16dB (158mV) output, selecting the 2nd measurement range group by a wide range discriminating circuit B. The said -16dBV output voltage is inputted to narrow- range discriminating circuits C1 and C2 to be converted into a DC voltage VD2, and a comparator 31 generates an output because it is lower than 0.316V. Then, TRs 36 and 49 turn on and a -40dBV full-scale measurement range is selected. The output of the amplifier 3 is amplified 5 to 4dBV (1.58V), and -6dB is displayed on the 3.16V full-scale board of a voltmeter 7.</p> |
