Resistor 'absorbs' oscillation?

  • Thread starter lennybogzy
  • Start date
I have a tiny bit of current fluctuation on one of my lines. If i put a lil 500ohm resistor in the line the osillations on the other end substantially decrease.

Why?

Does the resistor effectively 'absorb' these oscillations?
 

Integral

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It is hard to say much without some knowledge of the circuit. If you could tell us more it would help.
 
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If you are talking about standing waves (oscillations) in transmission lines, then terminate the t-line with its characteristic impedance; e.g., 50 ohms for RG-58. A t-line that is open at one end has a current node (voltage maximum) at the end, and reflects the forward signal..
Bob S.
 
Thanks for the replies.

Specifically I'm talking about a X96010 programmable current generator. My suspicion is that the analog temperature driven Vsense for this device is a bit unstable, normally unnoticable, but because there is a high speed LT1394 comparator with a relatively small hysteresis in the design, becomes a problem right around the switch point (otuput oscillates).

Might also have to do with the fact that the X96010 basically acts as an ADC, and I might be flopping between bytes.

Eithe way it is causing some current fluctuation, which seems to be improved if i put an (arbitrary) 499ohm resistor in the line. I'm trying to understand the fundamental reason for the improvement.
 
Depending on how long your line is, you could be suffering from oscillation between the source and line. Every line has a capacitance and if you switch a voltage vary quickly into that line, a current spike can be created. What it seems like is happening is that spike is bouncing back and forth between the line and your source; by adding the resistor (in series right?), you are slowing the rate at which the capacitance is charged, reducing the oscillation.
 
Depending on how long your line is, you could be suffering from oscillation between the source and line. Every line has a capacitance and if you switch a voltage vary quickly into that line, a current spike can be created. What it seems like is happening is that spike is bouncing back and forth between the line and your source; by adding the resistor (in series right?), you are slowing the rate at which the capacitance is charged, reducing the oscillation.
Yes the resistor is in series. Very interesting, thank you.
 
heres the pic, the current from the x96010 is what i believe osillates
 

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If the line from the x96010 is a twisted pair, I would out a ~70 ohm resistor upstream of the 0.1 uF capacitor. This plus the capacitor will be an effective termination for the twisted pair.
Bob S
 

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