Analog Dial AVO Amps-Volts-Ohms meter - del00023

This is a Amps Volts and Ohm Meter without a Display. It has a Potentiometer that has to be turned to make a measurement by watching the Bridge Balance LEDs switch ON state.



The real reason of doing this is to help students understand the various sections of parametric measurements. By building this you will learn more about analog design and instrumentation. 

This was designed, keeping in mind, that sometimes we have few components available and we could be flat broke. Even that you could not carry your DMM somewhere, but you have to make some instrument for a quick need with what is available.



If you are out of cash or feeling like Robinson Crusoe stranded in a place where you cant find any parts; then this is a low cost measurement system. I am not sure how this circuit may work, it is not tested . But i have built, repaired and designed many DMMs. So there is a fair chance, parts of it may work  :~)



PNG-Schematic   PDF-Circuit  

Analog Dial AVO Amps-Volts-Ohms meter - del00023


To view circuit. Click the Link of PNG or PDF and view the Circuit, PNG can be Scrolled with Mouse.
 
IC3 LM555 is to generate -5V from 9V.  In those days small firms used to make DPM's digital panel meters with 7107. In 1987  when i got a oppurtunity to design a DPM for a firm, I put the 555 clock in place CD4009 clock shown in intersil, to derive the -5 (-3V). 

This circuit is battery operated and has easily available LM324 quad Opamp and Timer LM555. Some Small signal Transistors and Diodes. Resistors and Caps. Yet it is difficult to build and make it work. You can even integrate a Digital or Analog meter after you learn and gain expertize. 



In those days other databooks i referred were from, TI, SGS and Fairchild.  So  most of these ideas with which  i design opmaps were learning that came from their application notes and datasheets. So read them and then you can understand these circuits.

The Source File in Cadsoft Eagle - del00023.zip.

 

Potentiometer Dial GIF for above circuit to be used to make a hand-held avo-meter.

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