Fluke 179 Diode Test - Page 1
Forum section: electronics / testgear

author: Electro Fan
author_rank: Super Contributor
timestamp: September 28, 2020, 01:53:31 am
content: Anyone happen to have a Fluke 179 that shows about 7.3 volts on the diode test?

author: paulbt
author_rank: Regular Contributor
timestamp: September 28, 2020, 07:50:58 am
content: Quote from: Electro Fan on September 28, 2020, 01:53:31 amHi, please post a picture with your setup.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 28, 2020, 02:28:59 pm
content: yep same thing .... post your setupthis meter should go up to 2.4v specified in the data sheets ...

author: markce
author_rank: Regular Contributor
timestamp: September 28, 2020, 07:39:08 pm
content: My Fluke 175 also has 7.3V output in diode test.What is specified is the max diode voltage that can be measured, not the test voltage.So I can test a 2.1V stabistor (integrated 3x Si diode), but not a 2.8V stabistor.

author: tubularnut
author_rank: Regular Contributor
timestamp: September 28, 2020, 07:46:54 pm
content: Like this?

author: Electro Fan
author_rank: Super Contributor
timestamp: September 28, 2020, 08:59:23 pm
content: Quote from: tubularnut on September 28, 2020, 07:46:54 pmSorry it took me a while to get back to this thread but yes, just like that.

author: tubularnut
author_rank: Regular Contributor
timestamp: September 28, 2020, 09:24:05 pm
content: Yes, very odd, not something I've not tried before, and the spec does say 2.4 volts as mentioned by coromonadalixThe Brymen shows 2.9V. The spec sheet says 2V but also an open circuit voltage of <3.5V, so maybe it has something to do with being (effectively) open circuit?I'm sure someone will come along and say we are doing it wrongPS. Apologies for the grubby look of the 179, it's my 'outside' meter, and well used.

author: PushUp
author_rank: Regular Contributor
timestamp: September 29, 2020, 12:55:07 am
content: The only device I have, is the "atlas Peak ZEN50", which is able to measure such high values in forward voltage mode.The first LED shows 2,63V and you see at least a flickering while testing - probably not on the picture, the second LED shows 8,50V and is not lighting up @ 2mA any more.From my experience, the better Keysights have the highest capability, but not as good as the green lantern from above.In this case my good old Hameg with its componenten tester, is the only device to illuminate the LED with probably 5-6 V(f) - no other from my DMMs can do so.Finally an example with an voltage regulator. Only Keysight and my HMC8012 are able to show a value - both 179 and 289 only "OL".Therefore the value of 7,298 VDC in diode mode against another DMM does not stand for the real capability of the DMM in normal bench usage - unfortunately...Cheers!

author: Electro Fan
author_rank: Super Contributor
timestamp: September 29, 2020, 05:14:42 pm
content: Thanks for the various test results and posts but I'm still trying to sort out the various meter specs as they relate to the results.Apparently some meter voltage specs for diode testing are an open circuit value and some specs better reflect voltage under some (generally not specified) load?Maybe what we are seeing is that DMM voltage specs might or might not specify everything needed to fully understand the diode test capability? Maybe the diode specs don't always show or reflect the DMM test's current limit value for the diode test?

author: PushUp
author_rank: Regular Contributor
timestamp: September 30, 2020, 05:00:09 pm
content: Inspired by your last question I was a bit curious and tried to measure the current of the Fluke 179 vs. Keysight U1272A while being in diode mode, than measuring a green LED and back to diode mode again, with just putting in and pulling out the red probe connected to the anode of a green LED to get an understanding of the different characteristics...Fluke 179:2nd: "flat Eric"Keysight U1272A:2nd: "rising Sun"...of course without laying claim to have a professional test installation...but it was fun!Cheers!

author: Electro Fan
author_rank: Super Contributor
timestamp: September 30, 2020, 06:03:15 pm
content: Quote from: PushUp on September 30, 2020, 05:00:09 pmThanks for doing that. I've run some additional/similar tests but haven't documented them so nice.Do you have any conclusions as to what's what with the various specs and measurements?

author: HKJ
author_rank: Super Contributor
timestamp: September 30, 2020, 08:02:18 pm
content: Quote from: PushUp on September 30, 2020, 05:00:09 pmNice to see some usage of TestController, but you could make the scale better. Select "Scales for chart", find the actual scale and put a check mark in the SI column.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 01, 2020, 09:59:40 pm
content: diode measurements with 34465A

author: Wytnucls
author_rank: Super Contributor
timestamp: October 02, 2020, 11:07:42 am
content: Did a quick comparison between my multimeters in diode mode:The most accurate ones are the Keithley and Rigol, which have a fairly high open voltage.

author: HKJ
author_rank: Super Contributor
timestamp: October 02, 2020, 11:16:40 am
content: Quote from: Wytnucls on October 02, 2020, 11:07:42 amThe meter may show the voltage accurately, but it cannot show the diode forward voltage accurately, because it depends on the current.I did write a bit about it in my article about using multimeters to test components:https://lygte-info.dk/info/DMMComponentTesting%20UK.html#DiodesI have also measured voltage and current at 3 points (open, short, max reading) for well over 100 meters in my reviews:https://lygte-info.dk/info/DMMReviews.html

author: Wytnucls
author_rank: Super Contributor
timestamp: October 02, 2020, 01:45:46 pm
content: Of course, that makes sense.I included the test current for a single diode, for comparisonFor the Keithley and Rigol, the test current remains constant throughout, due to their high compliance voltage .