/challenges-projects/project14/555timermadness/b/blog/posts/dual-tlc555-capacitance-meter-0-1pf-resolution-1960295403Two 555 timers turn capacitance into an analog voltage readable on a DMM. With a modern 600.00mV scale, that is readable to 10e-11F. I became an avid user of the 555 timer shortly after Radio Shack started carrying the first 555 timers in the &#39;70...en-USTelligent Community 12https://community.element14.com/challenges-projects/project14/555timermadness/b/blog/posts/dual-tlc555-capacitance-meter-0-1pf-resolution-1960295403Thu, 20 Oct 2022 18:06:13 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:29045189-daaf-44d5-a946-20ab339158cddougw0<p>That is awesome sensitivity. I used to use an LM2907 which is well suited to convert capacitance to frequency.</p><img src="https://community.element14.com/aggbug?PostID=24605&AppID=388&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/challenges-projects/project14/555timermadness/b/blog/posts/dual-tlc555-capacitance-meter-0-1pf-resolution-1960295403Tue, 18 Oct 2022 21:12:05 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:29045189-daaf-44d5-a946-20ab339158cdshabaz1<p>Nice!</p> <p>That&#39;s a very popular but super-effective topology, that gives good results. I&#39;m tempted to make this for the fixed 200 pF range. Also, this topology is very convenient for adapting for digital readout, by connecting that output from pin 3 directly into a microcontroller, and counting the width using rising/falling interrupts.</p><img src="https://community.element14.com/aggbug?PostID=24605&AppID=388&AppType=Weblog&ContentType=0" width="1" height="1">