Active attenuator - for measuring instruments

active attenuator R6 1% C7■ 4P7 12 V for measuring instruments 7 1C2 LF 356 RIO Pt 10k lin. 4 3 C10 C13 4,17 16 V ZPD10 D3 1P D2 ZPD10 82513 0O 12V R11 612 12 V J. Bartels 7-24 — elektor july/august 1982 Although countless measuring instrument preamps have been published in recent years, none of them would have served their purpose, if they could not attenuate the input signal. This is required, in order to ensure that the full scale of the measuring instrument is utilised to the full. As a matter of interest the attenuation, in most cases, is effected in steps of 1,2 or 5. The circuit described here divides the input signal into 12 steps covering a range from 5 mV (the most sensitive setting) to 20 V. Capacitors C2 ... C6 are included for frequency compen- sation. The range switch consists of two twelve way wafers, SI a and Sib. With the help of S1a the input signal is divided into 4 attenuation steps. At the same time S1b allows the gain of IC1 to be adjusted in three step...