Ceramic Filter(PFS455A) 455kHz Testing Issue

[syedhamzahasan]

Hello All,

Recently I bought a ceramic filter PFS455A of 455kHz for my receiver project. I wanted to test it independently first to see its response on oscilloscope. I made the test circuit mentioned in it's datasheet and connected with signal generator, nothing came on oscilloscope, as if it wasn't even present in the circuit. I am not sure what I'am doing wrong, checked the soldering and connectivity twice, replaced the filter twice as well. Any advise would be appreciated.

 

[schmitt trigger]

I would suggest the following:

1) Connect CH1 scope probe at the filter's pin 1. Trigger your scope with this signal.
2) Connect CH2 scope probe at the filter's pin 3.

If you can't see anything, try disconnecting pin 2 from ground.

 

[BigBoss]

Ceramic Filters need a bit high driving levels.Could you arrange it ??

 

[syedhamzahasan]

I would suggest the following:

1) Connect CH1 scope probe at the filter's pin 1. Trigger your scope with this signal.
2) Connect CH2 scope probe at the filter's pin 3.

If you can't see anything, try disconnecting pin 2 from ground.

I did that and saw nothing. Any other suggestions?

 

[syedhamzahasan]

Ceramic Filters need a bit high driving levels.Could you arrange it ??

Yes I can. How high are we talking about? Right now we are giving 1v

 

[BigBoss]

Yes I can. How high are we talking about? Right now we are giving 1v

1Vrms is high enough.The resonator may be broken ?? Or an measurement error ??

 

[betwixt]

Assuming RF 'good practice' was used in the testing, I can't see any reason why it shouldn't work.

Have you tried sweeping the signal generator frequency a few 10s of Khz each side of expected resonance? Do you see any output at all doing that?

Brian.

 

[vfone]

Google for "wobbulator schematic" and you will find a lot of simple circuits that allow to get the shape of ceramic filters using a simple XY oscilloscope.

 

[syedhamzahasan]

Assuming RF 'good practice' was used in the testing, I can't see any reason why it shouldn't work.

Have you tried sweeping the signal generator frequency a few 10s of Khz each side of expected resonance? Do you see any output at all doing that?

Brian.

Yes I tried that nothing appears as if the circuit is not even present between the test equipment. I have tried this circuit and my own circuits and no results........Will try a new filter this one was a cheap china copy I think.........I can think of no other reason.

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Google for "wobbulator schematic" and you will find a lot of simple circuits that allow to get the shape of ceramic filters using a simple XY oscilloscope.

OK will try that. Thanks

 

[betwixt]

There is something else you could try:
Wire up as in the test circuit but connect a 2-channel scope with one probe at the filter input pin and the other at the output pin. It will show whether the input side is attenuating the signal as well as passage at resonance. It may be that there is no signal entering the filter for whatever reason.
Use x10 scope probes to minimize loading!

Brian.

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