Wednesday, September 24, 2014

Precision Audio Milli volt meter Circuits Diagram

This electronic circuit is audio milivolt meter. It measures 10mV to 50Volt RMS in eight ranges.

Precision Audio Millivoltmeter Circuits Diagram

Precision Audio Millivoltmeter Circuits Diagram
 
 Notes:
  • Connect J2 and J3 to an Avo-meter set to 50µA range:
  • Switching SW2 the four input ranges will be multiplied by 5
  • Total fsd ranges are: 10mV, 50mV, 100mV, 500mV, 1V, 5V, 10V, 50V
  • Set R11 to read 1V in the 1V range, with a sine wave input of 1V @ 1KHz
  • Compare the reading with that of another known precision Millivoltmeter or with an oscilloscope.
  • The oscilloscope reading must be a sinewave of 2.828V peak to peak amplitude
  • Frequency response is flat in the 20Hz-20KHz range
  • If you have difficulties in finding resistor values for R1, R2, R3 & R4, you can use the following trick:
    R1 = 10M + 1M in parallel
    R2 = 1M + 100K in parallel
    R3 = 100K + 10K in parallel
    R4 = 1K2 + 6K8 in parallel
    All resistors 1/4W 1% tolerance 

Parts:

R1_____909K    1/2W 1% Metal Oxide Resistor
R2______90K9   1/2W 1% Metal Oxide Resistor
R3_______9K09  1/2W 1% Metal Oxide Resistor
R4_______1K01  1/2W 1% Metal Oxide Resistor
R5_____100K    1/4W Resistor
R6_______2M2   1/4W Resistor
R7______82K    1/4W Resistor
R8______12K    1/4W Resistor
R9_______1K2   1/4W Resistor
R10______3K3   1/4W Resistor
R11____200R    1/2W Trimmer Cermet
 
C1_____330nF   63V Polyester Capacitor
C2,C3__100µF   25V Electrolytic Capacitor
C4_____220µF   25V Electrolytic Capacitor
C5______33pF   63V Polystyrene Capacitor
C6_______2µ2   63V Electrolytic Capacitor
 
D1-D4___1N4148 75V 150mA Diodes
 
IC1_____CA3140 Op-amp
IC2_____CA3130 Op-amp
 
SW1_____2 poles 5 ways rotary switch
SW2_____SPDT switch
 
J1______RCA audio input socket
J2,J3___4mm. output sockets
 
B1______9V PP3 Battery
 
Clip for PP3 Battery

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