Post History
As the title says, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist....
#8: Post edited
by
Lorenzo Donati
·
2023-07-29T20:40:51Z (10 months ago)
#7: Post edited
by
Lorenzo Donati
·
2023-07-29T20:04:32Z (10 months ago)
#6: Post edited
by
Lorenzo Donati
·
2023-07-29T20:03:31Z (10 months ago)
#5: Post edited
by
Lorenzo Donati
·
2023-07-29T18:29:55Z (10 months ago)
#4: Post edited
by
Lorenzo Donati
·
2023-07-29T18:28:56Z (10 months ago)
#3: Post edited
by
Lorenzo Donati
·
2023-07-13T17:42:27Z (10 months ago)
As the title say, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist.- In particular:
- + Digital oscilloscope with 50MHz bandwidth and simple passive probes (x1, x10).
- + Function generator with 20Mhz frequency max.
- + Common electronic parts found in didactic labs (1% resistors, 5% capacitors).
- The technique should produce results with decent accuracy, possibly 10% or better and it should be applicable to small sections of cable (it shouldn't require an entire cable reel), so just 1 or 2 meters or so (better if applicable to a more manageable ~50cm section).
- It should also be applicable to the most common cables used to carry analog and digital signals in non-specialty applications (e.g. RG58, RG59, RG174, twisted pairs in cat5+ ethernet cables, etc.).
- Bonus points if it's applicable also to differential pairs with controlled impedance on PCBs.
- If possible, the technique should not require precise measurement of the cable length (hopefully no such measurement should be necessary).
- Bonus points if the technique doesn't require complex math formulas, but some math is acceptable. It's OK if the formula(s) is not too easy to compute by hand or hand calculator, but it should be implementable on a spreadsheet without complications (so no integrals or derivatives).
The idea is to have a setup that could let even a newbie high-school student to perform the measurement without too much hassle.
- As the title says, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist.
- In particular:
- + Digital oscilloscope with 50MHz bandwidth and simple passive probes (x1, x10).
- + Function generator with 20Mhz frequency max.
- + Common electronic parts found in didactic labs (1% resistors, 5% capacitors).
- The technique should produce results with decent accuracy, possibly 10% or better and it should be applicable to small sections of cable (it shouldn't require an entire cable reel), so just 1 or 2 meters or so (better if applicable to a more manageable ~50cm section).
- It should also be applicable to the most common cables used to carry analog and digital signals in non-specialty applications (e.g. RG58, RG59, RG174, twisted pairs in cat5+ ethernet cables, etc.).
- Bonus points if it's applicable also to differential pairs with controlled impedance on PCBs.
- If possible, the technique should not require precise measurement of the cable length (hopefully no such measurement should be necessary).
- Bonus points if the technique doesn't require complex math formulas, but some math is acceptable. It's OK if the formula(s) is not too easy to compute by hand or hand calculator, but it should be implementable on a spreadsheet without complications (so no integrals or derivatives).
- The idea is to have a setup that could let even a newbie high-school student perform the measurement without too much hassle.
#2: Post edited
by
Lorenzo Donati
·
2023-07-11T19:33:46Z (10 months ago)
- As the title say, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist.
- In particular:
- + Digital oscilloscope with 50MHz bandwidth and simple passive probes (x1, x10).
- + Function generator with 20Mhz frequency max.
+ Common electronic parts found in didactic labs (1% resistors, 5% caps)- The technique should produce results with decent accuracy, possibly 10% or better and it should be applicable to small sections of cable (it shouldn't require an entire cable reel), so just 1 or 2 meters or so (better if applicable to a more manageable ~50cm section).
- It should also be applicable to the most common cables used to carry analog and digital signals in non-specialty applications (e.g. RG58, RG59, RG174, twisted pairs in cat5+ ethernet cables, etc.).
- Bonus points if it's applicable also to differential pairs with controlled impedance on PCBs.
- If possible, the technique should not require precise measurement of the cable length (hopefully no such measurement should be necessary).
- Bonus points if the technique doesn't require complex math formulas, but some math is acceptable. It's OK if the formula(s) is not too easy to compute by hand or hand calculator, but it should be implementable on a spreadsheet without complications (so no integrals or derivatives).
- The idea is to have a setup that could let even a newbie high-school student to perform the measurement without too much hassle.
- As the title say, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist.
- In particular:
- + Digital oscilloscope with 50MHz bandwidth and simple passive probes (x1, x10).
- + Function generator with 20Mhz frequency max.
- + Common electronic parts found in didactic labs (1% resistors, 5% capacitors).
- The technique should produce results with decent accuracy, possibly 10% or better and it should be applicable to small sections of cable (it shouldn't require an entire cable reel), so just 1 or 2 meters or so (better if applicable to a more manageable ~50cm section).
- It should also be applicable to the most common cables used to carry analog and digital signals in non-specialty applications (e.g. RG58, RG59, RG174, twisted pairs in cat5+ ethernet cables, etc.).
- Bonus points if it's applicable also to differential pairs with controlled impedance on PCBs.
- If possible, the technique should not require precise measurement of the cable length (hopefully no such measurement should be necessary).
- Bonus points if the technique doesn't require complex math formulas, but some math is acceptable. It's OK if the formula(s) is not too easy to compute by hand or hand calculator, but it should be implementable on a spreadsheet without complications (so no integrals or derivatives).
- The idea is to have a setup that could let even a newbie high-school student to perform the measurement without too much hassle.
#1: Initial revision
by
Lorenzo Donati
·
2023-07-11T19:32:58Z (10 months ago)
Is there an easy way to measure the characteristic impedance of a cable using basic lab instruments?
As the title say, I'm interested in a simple technique to measure the characteristic impedance of a cable using only the instruments available in a school lab or to a (somewhat advanced) hobbyist. In particular: + Digital oscilloscope with 50MHz bandwidth and simple passive probes (x1, x10). + Function generator with 20Mhz frequency max. + Common electronic parts found in didactic labs (1% resistors, 5% caps) The technique should produce results with decent accuracy, possibly 10% or better and it should be applicable to small sections of cable (it shouldn't require an entire cable reel), so just 1 or 2 meters or so (better if applicable to a more manageable ~50cm section). It should also be applicable to the most common cables used to carry analog and digital signals in non-specialty applications (e.g. RG58, RG59, RG174, twisted pairs in cat5+ ethernet cables, etc.). Bonus points if it's applicable also to differential pairs with controlled impedance on PCBs. If possible, the technique should not require precise measurement of the cable length (hopefully no such measurement should be necessary). Bonus points if the technique doesn't require complex math formulas, but some math is acceptable. It's OK if the formula(s) is not too easy to compute by hand or hand calculator, but it should be implementable on a spreadsheet without complications (so no integrals or derivatives). The idea is to have a setup that could let even a newbie high-school student to perform the measurement without too much hassle.