Fluke 189 Capacitance Measurement - Page 1
Forum section: electronics / testgear

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2018, 02:23:42 am
content: If you own a 189 and FlukeView, I am curious in the capacitance mode on the nF range, what resolution is reported?I am finally getting around to trying one out with LabVIEW and notice that it reports a 100fF resolution. From the data it sends, this appears correct. I'm curious if their software displays this added digit.

author: commongrounder
author_rank: Frequent Contributor
timestamp: December 02, 2018, 04:25:08 pm
content: So, I have Flukeview Forms. A super clunky program, but it does the job. I have two meters that interface with this program. One is a Fluke 89iv, which is the direct predecessor of the 189, and works almost identically. The other is a Tektronix DMM4050, which we know is a close relative of the Fluke 8846a. The Tek communicates with Flukeview through Fluke 45 meter compatibility mode, with an extended command set that includes functions not available on the Fluke 45.I ran a logging test on each meter and charted the results. I set up to measure nF capacitance with a tuning cap to allow slight varying of the value. They both behaved identically, so I’ve attached the 89iv chart and partial data. As you can see it only records the same number of digits the meters display. Interesting. So it would seem that LabVIEW is able to extract more data resolution, at least from a 189.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2018, 06:21:08 pm
content: Thanks for checking. I checked the other functions of the 189 and it appears that it is only the capacitance that has a higher resolution. I wasn't able to find any reference to it in the manuals.I ran a quick test where I zeroed out the meter and then trimmed the capacitor to 0pF. I let the meter sit about 15 minutes and then swept the cap to 10pF. It's still on my desk as shown in the first picture and you can see the effects of me walking in and sitting down.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2018, 06:23:57 pm
content: If I zoom into the area where I had zeroed out the meter and let it sit, plotting a histogram we can see the meter is fairly stable. Maybe even more stable than some meters looking at 0.01nF. We can also clearly see that the 100fF resolution is real data.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2018, 06:29:26 pm
content: This is looking at the last bit of data where I slowly adjust the capacitor to 10pF. It's odd the meter would have this resolution but they chose not to exploit it. My guess is they took the more conservative approach and did not want the backlash of people complaining about it.

author: commongrounder
author_rank: Frequent Contributor
timestamp: December 02, 2018, 07:35:52 pm
content: Quote from: joeqsmith on December 02, 2018, 06:21:08 pmHa! That’s great! You just reinvented the condenser microphone! Probably has a few problems with flatness and response bandwidth, though.Really interesting how stable the meter is, and the essentially hidden capacitance resolution.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2018, 10:42:41 pm
content: Winter coming and the house is starting to dry out. It's that time of the year when static starts to be a problem. Time to put the UNI-T meters away...Looking at a 1.9Megohm with the meter about 5 feet from me while rubbing my feet on the carpet floor.