Tuesday, October 11, 2011

Testing the Sangamd 10kHz Low Pass Filter

Tonight I took a quick look at an old Sangamd 10kHz low pass filter. Here is a snapshot of the filter and all of it's majesty! It's a beautiful old piece in excellent physical condition.


Physically, the unit is 1.7" x 1.6" x .8". The leads have an outer diameter of .025". The inner diameter of the round-casing that surrounds the leads is approximately .130". The height of the lead that extends above the casing is roughly .090", this does not leave much room for pressing the unit into a breadboard. I ended up using some old wire wrap, stripping it and tying it around the leads. Here is a closeup of the wire wrap around the leads.


Three wires stripped, wrapped and pressed by hand. Piece of cake!! At least it looks that way from the image. It takes a minute or so to get the wrap just tight enough to slip over the lead. Here is a snapshot of what all of the completed wire extensions looked like.


Now, we will plug it all into a breadboard and feed 1, 2, 3, 4.... 10kc, etc, while observing the output in-and-around 10kc. In the shot below, I am feeding 10kc @ 1Vpp into it. Here you are seeing what the oscope reads at the output of the filter. Not bad!


Now 12kc.



Now 13kc.



Now 14kc.


Now 15kc. Notice the dip.



Now 16kc, notice the dip again.



And now, 17kc.


The true drop-off point for the filter is somewhere between 13 and 15kc. I will dig a bit more to determine a closer estimate for the drop off. Unfortunately, I am unable to find a specification for this unit online, so it is impossible to say whether or not it is performing within its designed tolerances. For its age, I would say the unit appears to be working well!

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