I'm measuring up to 10 MHz, with the following setup. The source is a 0.2 ohm resistor. Will I maintain accuracy, without 50 ohm at each end? Does it need a series 50 ohm resistor at the source? Does it matter, at 10 MHz with only 2ft of coax?
|-------+--------| | | | ___________________ AC [0.2] BNC ____2ft of R-58____ BNC---50 ohm Probe to | | | RF millivolt Meter | | | === === ===
Thanks, Mikek
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Not if the RF meter is 50 ohms. If the meter is HiZ, add a source-end resistor.
Not much.
You could Spice this.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I think you might need a 50 ohm resistor at the probe end only. I would see if there is a difference in readings with and without a 50 ohm resistor there. If your probe presents a 50 ohm load to that end of the line, then no additional 50 ohm resistor is needed.
Depends on what you're measuring for. If you're looking for the power delivered to a 50-ohm load then you don't care about the source impedance
-- just that the load is 50 ohms. So you don't need the series resistor.
If, OTOH, you were planning on _putting_ that 50-ohm series resistor in there later, then yes, clearly you need it.
-- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com
I'm putting a millivolt meter with a 50 ohm input impedance at the end of the coax. I want know that the voltage the meter reads at the end of the coax, is equal to the source voltage. Mikek
I believe it will be.
-- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com
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