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Measuring A Cap

Joe WB9SBD All Messages By This Member #26962 What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Should I set the stimulus rage for those values? And the measurement should be taken when the smith chart tracer thing is right at the bottom like 6 O'clock position correct? Joe WB9SBD / W9ET
W0LEV All Messages By This Member #26968 It's best to measure the capacitor at the frequency of interest, especially as that frequency increases. For a "sticker value", use a low frequency - 1 MHz or less. As the frequency increases, parasitic inductance becomes more and more evident which cancels some of the effective capacitance. Dave - W?LEV toggle quoted message Show quoted text On Sun, Feb 20, 2022 at 2:52 PM Joe WB9SBD <nss@...> wrote: What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Should I set the stimulus rage for those values? And the measurement should be taken when the smith chart tracer thing is right at the bottom like 6 O'clock position correct? Joe WB9SBD / W9ET -- Dave - W?LEV Just Let Darwin Work
Roger Need All Messages By This Member #26970 On Sun, Feb 20, 2022 at 06:52 AM, Joe WB9SBD wrote: What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Here is a previous post where I show how to measure a 365 pF cap in this frequency range.... /g/nanovna-users/message/25725 This post was a response to this post >> /g/nanovna-users/topic/87236912#25714 Roger
Joe WB9SBD All Messages By This Member #26971 I am sorry that I asked that question again. I'm Old, The Brain is failing. I am lucky when i go to the basement to get a tool, to be able to remember what tool I went down there to get. Sorry, Joe WB9SBD / W9ET
Max All Messages By This Member #26972 You're not the only one. Oh wait, what were we talking about? Max toggle quoted message Show quoted text On Sunday, February 20, 2022, 01:13:22 PM CST, Joe WB9SBD <nss@...> wrote: I am sorry that I asked that question again. I'm Old, The Brain is failing. I am lucky when i go to the basement to get a tool, to be able to remember what tool I went down there to get. Sorry, Joe WB9SBD / W9ET
Joe WB9SBD All Messages By This Member #26974 oK, UST TRIED WITH A STIMULUS SPAN OF 3.5 TO 4 MEG. Oops cap lock, anyway. The smith chart curve starts at the far right, short? or open? UG memory again,,, anyway the curve starts at the far right, but only curves down to say the 4 to 5 o clock position it doesn't get to the bottom of the display. so Now what? Joe WB9SBD / W9ET toggle quoted message Show quoted text On 2/20/2022 12:20 PM, W0LEV wrote: It's best to measure the capacitor at the frequency of interest, especially as that frequency increases. For a "sticker value", use a low frequency - 1 MHz or less. As the frequency increases, parasitic inductance becomes more and more evident which cancels some of the effective capacitance. Dave - W?LEV On Sun, Feb 20, 2022 at 2:52 PM Joe WB9SBD<nss@...> wrote: What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Should I set the stimulus rage for those values? And the measurement should be taken when the smith chart tracer thing is right at the bottom like 6 O'clock position correct? Joe WB9SBD / W9ET
W0LEV All Messages By This Member #26977 You don't "need" the bottom of the chart which is -j50. Read your value midband on the measured curve at 3.750 MHz (not critical). Extreme right on the Smith Chart is an open while the extreme left is a short - both on the horizontal line. Dave - W?LEV toggle quoted message Show quoted text On Sun, Feb 20, 2022 at 7:48 PM Joe WB9SBD <nss@...> wrote: oK, UST TRIED WITH A STIMULUS SPAN OF 3.5 TO 4 MEG. Oops cap lock, anyway. The smith chart curve starts at the far right, short? or open? UG memory again,,, anyway the curve starts at the far right, but only curves down to say the 4 to 5 o clock position it doesn't get to the bottom of the display. so Now what? Joe WB9SBD / W9ET On 2/20/2022 12:20 PM, W0LEV wrote: It's best to measure the capacitor at the frequency of interest, especially as that frequency increases. For a "sticker value", use a low frequency - 1 MHz or less. As the frequency increases, parasitic inductance becomes more and more evident which cancels some of the effective capacitance. Dave - W?LEV On Sun, Feb 20, 2022 at 2:52 PM Joe WB9SBD<nss@...> wrote: What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Should I set the stimulus rage for those values? And the measurement should be taken when the smith chart tracer thing is right at the bottom like 6 O'clock position correct? Joe WB9SBD / W9ET -- Dave - W?LEV Just Let Darwin Work
Joe WB9SBD All Messages By This Member #26978 Thanks Dave! Joe WB9SBD /W9ET toggle quoted message Show quoted text On 2/20/2022 2:05 PM, W0LEV wrote: You don't "need" the bottom of the chart which is -j50. Read your value midband on the measured curve at 3.750 MHz (not critical). Extreme right on the Smith Chart is an open while the extreme left is a short - both on the horizontal line. Dave - W?LEV On Sun, Feb 20, 2022 at 7:48 PM Joe WB9SBD<nss@...> wrote: oK, UST TRIED WITH A STIMULUS SPAN OF 3.5 TO 4 MEG. Oops cap lock, anyway. The smith chart curve starts at the far right, short? or open? UG memory again,,, anyway the curve starts at the far right, but only curves down to say the 4 to 5 o clock position it doesn't get to the bottom of the display. so Now what? Joe WB9SBD / W9ET On 2/20/2022 12:20 PM, W0LEV wrote: It's best to measure the capacitor at the frequency of interest, especially as that frequency increases. For a "sticker value", use a low frequency - 1 MHz or less. As the frequency increases, parasitic inductance becomes more and more evident which cancels some of the effective capacitance. Dave - W?LEV On Sun, Feb 20, 2022 at 2:52 PM Joe WB9SBD<nss@...> wrote: What is a typical stimulus range for measuring a Cap? If it makes any difference it is a 500pf cap, and is used between 3.5 and 4 Mhz. Should I set the stimulus rage for those values? And the measurement should be taken when the smith chart tracer thing is right at the bottom like 6 O'clock position correct? Joe WB9SBD / W9ET

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