Multimeter feedback

[ennisdavis]

What am I going wrong here. I am making a multi meter and have 2 wave bridge rec. with different resistance, one for 0-15, other 100-600vac. The 2 fight each other and blow the power supply. I have tried a diode from the meter inputs to each wave bridge but it didnt work.

 

[gophert]

I think you need to use google to find a better circuit.

 

[Pommie]

The outputs of the righthand bridge both go to the same terminal.

Mike.

 

[JimB]

As drawn, the polarity of some of the diodes in the bridges are incorrect.

Terminology: the bridges are "bridge rectifiers" or "full wave bridge rectifiers", but not "wave rectifiers"

JimB

 

[audioguru]

I show the correct way a full wave bridge rectifier is made.
You need only one bridge rectifier plus the two resistors. The resistors are switched.

Your idea produces serious voltage errors because an ordinary bridge rectifier reduces the peak or average output voltage by about 1.4V.
Then a peak input of 15V produces a peak output of 13.6V and a peak input of 2V produces a peak output of 0.6V. A peak input of 1.5V produces a peak output of 0.1V. You need an opamp that makes an active rectifier to cancel the 1.4V error.