Is there any small capacitance/Q meter out there for small RF capacitors? - Page 1
Forum section: electronics / rf-microwave

author: rf-fil
author_rank: Regular Contributor
timestamp: July 20, 2018, 01:54:32 am
content: I have a VNA, which is perfect for measuring small capacitors, but I often have it hooked up to something else.. So I'm looking for some hand-held tweezer-like meter that can accurately measure small capacitances, 0.1pF to 100pF and also the tangent delta.Btw, normal multimeters or cheap capacitance meters from ebay are not good - they show the wrong capacitance when tangent delta is too high. And they don't really work that well with capacitors below maybe 10pF.My use cases are:- checking that I have the correct 0402 / 0603 / etc. capacitor- checking PCB test coupons- measuring trimmer capacitors prior to replacement with corresponding fixed valuesSo, it's really measurement of impedances that happen to be mostly capacitive. But let's call it a capacitance meter :-).What are the suggestions? Kits, pro instruments can all be considered.

author: mtdoc
author_rank: Super Contributor
timestamp: July 20, 2018, 03:01:31 am
content: The DE-5000 handheld LCR meter has 0.01pF resolution at its lowest range. I believe it can be found for about $100 on eBay.

author: tautech
author_rank: Super Contributor
timestamp: July 20, 2018, 03:08:44 am
content: For a pro and trustworthy tool, ST5S tweezers.http://www.smarttweezers.com/st5s/

author: mtdoc
author_rank: Super Contributor
timestamp: July 20, 2018, 03:13:44 am
content: Those ST5S tweezers always look so cool. I wish I could justify buying some for my modest hobbyist pursuits...

author: tautech
author_rank: Super Contributor
timestamp: July 20, 2018, 03:25:31 am
content: Quote from: mtdoc on July 20, 2018, 03:13:44 amOnly a few here own them since many have seen one of Daves early vids I think on the same set I have, ST3 and really for a top PCB guy Dave had no idea how capable these things really are. I use mine more than a DMM or a scope.I've had these for years and would replace them in an instant.Study the specs and accuracy and they come with a Cal cert.They're a 4 wire device and not restricted to SMD and that's the big mistake ppl make when not considering them.I put all hobby spending on hold for a while in order to afford them way back then when all I had was a CRO and a shitty DMM.IIRC blueskull got a set based on my recommendation and hasn't been disappointed.Good tools just cost !

author: Teuobk
author_rank: Contributor
timestamp: July 21, 2018, 05:31:13 pm
content: The DE-5000 can do even better than 0.1 pF: in the 200 pF range, it has a resolution of 0.01 pF with accuracy of 1.2% + 5 counts (when using a 10 kHz test frequency) or 2.0% + 5 counts (when using 100 kHz).Part of the trouble of measuring really small capacitance values with tweezers is that the tweezers themselves can add significant capacitance. However, if you zero the system with the tweezers held about 4 thou apart, as would be the case when measuring an 0402, you can null out most of that effect.Here's a photo of me measuring a 1.2 pF low-ESR 0402 cap this morning with my DE-5000 and its tweezers attachment:I was measuring at 100 kHz, and had previously zeroed the system with the tweezers positioned as described above, so with the indicated value of 1.19 pF, the actual value should be in the range 1.11 pF to 1.26 pF. That's good enough for me, especially since these are +/- 10% caps anyway, and the nominal value is 1.2 pF.

author: mtdoc
author_rank: Super Contributor
timestamp: July 21, 2018, 06:22:20 pm
content: Quote from: Teuobk on July 21, 2018, 05:31:13 pmRight you are! I corrected my post.

author: CopperCone
author_rank: Super Contributor
timestamp: July 22, 2018, 02:58:59 pm
content: Quote from: rf-fil on July 20, 2018, 01:54:32 amWhat setups do you use with the VNA for single component measurements?

author: rf-fil
author_rank: Regular Contributor
timestamp: July 23, 2018, 01:35:53 am
content: QuoteSimple, a piece of semi-rigid coax with soldered on pogo pins. This works for PCB coupons and small caps as well. I run these measurements somewhere down low, like 10MHz.

author: rf-fil
author_rank: Regular Contributor
timestamp: July 23, 2018, 01:39:14 am
content: The DE-5000 looks decent. Ordered.Agreed re calibrating the tweezers in the exact position, just prior to taking the measurement. Any kind of cable + probe has at least a few pF of its own capacitance.

author: CopperCone
author_rank: Super Contributor
timestamp: July 23, 2018, 06:45:35 pm
content: Quote from: rf-fil on July 23, 2018, 01:35:53 amDo you mean you get a piece of semi ridged coax, take a bite out of it to expose the inner structure but do not break the ground plane, so it looks like a bath tub shape, remove some of the inner structure carefully, then solder in pogo pins? That is one of the best ideas I have seen if thats what you mean. Can you take a picture anyway I am curious?Do you do any kind of series impedance or anything like that? If you watch Davejones most recent teardown video of the impedance analyzer they show different circuit that should be used with different impedances. As its wired I think a VNA will only give accurate information around 50 ohms impedance unless you modify the test setupAnd the De-5000 is good I have been using it for a long time but its 100KHz maximum leaves something to be desired for me. Also the alligator kelvin clip is poor quality (I had to resolder and the actual aligator clip was loose and the jaws did not close right) and the tweezers I found were not the friendliest, they have too much play and not enough grip in my opinion, if you compare them to real tweezers meant for picking stuff up. I would like to make them structurally stiffer so you can't torsionally distort them so easily, and I would like to see maybe some texturing on the grabber end. Small SMD parts are kind of annoying to probe, the contact pressure requires some skill.. if you give them too much pressure they will torque on you and the part goes missing some where on the floor.I have thought to modify real tweezers for LCR capability lol, so I can use nice swanstrom/lindstrom/etc ones.I find the trick to using the DE-5000 tweezers is to grip them very close to the end. Like 1cm above the probes, then you have marginally acceptable control. If I try to use them like my quality tweezers, gripping them about 1/2 way down, they are super fail. They still feel like they are made of fucking spaghetti though. You need to really watch your thumb.

author: cdev
author_rank: Super Contributor
timestamp: July 10, 2020, 12:17:16 pm
content: @rf-fil Your pogo pins SMD component test jig sounds very useful and is something I need to make and I'd very much appreciate seeing what you did, if its still working for you.I'm hoping to make one for use with a NanoVNA.@coppercone @coppercone2

author: ignilux
author_rank: Unknown
timestamp: July 10, 2020, 07:32:17 pm
content: You're responding to a thread that is 2 years old, but... I also wanna see that jig

author: mark03
author_rank: Frequent Contributor
timestamp: July 13, 2020, 02:58:37 am
content: Me too. I wonder if @rf-fil gets an email when his name comes up in an old thread?

author: cdev
author_rank: Super Contributor
timestamp: July 15, 2020, 03:19:18 am
content: I dont have a test jig for this set up to do this on my nanovna2 yet but I am very close to having one. There are three basic approaches to measuring the reactance of a component, load, shunt or through.yet but even without it you can do these measurements at much lower frequencies with through hole parts and might even be able to use the same fixtures used for them..It might be quite useful to simply set up a tweeser using the nanovna2And a ground. And a rf relay. and a fotswitch (say you needed to test a lot)This could make a practical setup that would filll a niche that doesnt seem to exist now well.I might normally want to know components performance but much higher than say my DER-5000 can do