Rectifier

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roronoa

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hi everyone, i rectified a AC signal using a a half wave rectifier, when i measure the current at the output, it seems to fluctuate(keeps on changing about +- 10mA from the actual value).

can anyone tell me how to solve this problem?can this be solved if i use a full wave rectifier instead of a half wave rectifier??? thanks for replying.
 

first use an oscilloscope to measure that how your output is.....
is it actually as you are saying or something else...
 
R u sure the current swings from positive to negative.in a rectifier the current cant flow in both directions.make sure the diode u r using is working properly
 
im using a multimeter to measure the current, i set it to DC mode since i already rectified it to a DC from AC using a half wave rectifier.

The value of the current should be around 150mA. but now my multimeter shows that the value keep on changing from 140-160mA. It wont stay still at a certain value.
 
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Sounds like your DMM is very simplistic. The reading variation results from the intrinsic "sampling" of the complex waveform. My $250 high quality DMM has a "true RMS" reading mode; my $5 Harbor Freight Cheapo Chinese DMM does not.
 
you said its a signal?? depends on the application you can use a capacitor to smooth it, so if you have no other option to check it with a good DMM then try to put a cap and check.
 

You're only getting a variation of a few percent. The grid voltage is not perfectly constant, and will cause some variation in the output current of a simple rectifier loaded with a resistive load.

Set your meter to measure AC voltage and connect it to the secondary of your transformer (the winding feeding the rectifier; I'm assuming you're using a transformer), and monitor that for a while; see if you don't get a slightly variable voltage.

If you know how to do it safely, you could measure the line voltage at the wall outlet and see if you don't also get variation there.
 
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the output you are geting is pulsating DC. so use a filter circuit to get pure DC output from it.... and then check the output. It could be because of ripples.
 
What is the load and is the load a constant? What rate (approximately) does the current change at?

Ron
 
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