Can Fluke clamp meter measure DC inrush current? - Page 1
Forum section: electronics / testgear

author: isso
author_rank: Contributor
timestamp: January 11, 2024, 04:21:50 pm
content: Hi,I'm thinking to purchase Fluke 355 or similar clamp meter, I need to measure the car starter maximum currents. Fluke instruction manual states that for Inrush measurements AC current mode should be selected. Does that mean that it cannot measure DC inrush current? Thanks

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 11, 2024, 05:18:49 pm
content: I think it can. The specs said it can. Only the manual said to turn the dial to ACA position.

author: G-son
author_rank: Regular Contributor
timestamp: January 12, 2024, 09:06:21 am
content: Have you considered a current probe with an oscilloscope instead of a clamp meter? Gives you a nice waveform where you can see peak as well as many other interesting things.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: January 13, 2024, 07:17:50 pm
content: Have no idea how accurate these inrush features are in stand-alone AC&DC clamp meters, not least for use in DC?as it is often a secondary feature with very little data, and what ms it needs for a given accuracy, and obviously centered around AC, so any DC info, are a fluke at best.DC inrush accuracy

author: MarkF
author_rank: Super Contributor
timestamp: January 13, 2024, 09:42:12 pm
content: I'm going to guess from the manual that the Fluke 355 can not measure DC inrush current.To measure inrush, the manual says to set the knob to AC current.

author: shapirus
author_rank: Super Contributor
timestamp: January 13, 2024, 10:54:28 pm
content: Not sure about the Fluke, but, for example, Brymen BM037 can do it ("CREST" mode).The time window in which the peak values are captured are specified in the manual (something around 1 ms, I believe).Mine, however, has a bug: it only measures it correctly in the 600A range. In the 60A range it shows readings about 4 times higher than actual values. No idea if it's only my unit or the whole batch or the whole product that have this glitch. I tried to contact the supplier, they did their best to try to solve this, they also tried to contact Brymen, but, alas, it finally ended with nothing.The 600A range is still very usable, though, even in the low-amps area, so it's not too big of an issue, however, of course, the 60A range CREST mode (only) glitch is rather unpleasant.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: January 14, 2024, 12:04:37 am
content: You can usually measure DC inrush on these clamp meters that packs " AC inrush feature", which is useally spec'ed for AC use-cases.Though have no idea what kind of accuracy you actually obtain when using "inrush" on DC usecases..Mostly the higher-end Fluke clamp meters, that I recall also mention DC on the inrush.. fx Fluke 345PQI purchased a cheap welder so I could fiddle with fast & high amp/current bursts, both on stand alone clamp meters with inrush, and on AC&DC clamp meters for scope.It's a welder from China, its self-contained construction makes it easy to test with and gives more than one amp-burst.Gives me control over the pre-burst 0-10ms & the main-burst 1-80ms alongside an adjustable 0.5 to 2.5sec delay.price was around 22 US (incl. 25% VAT & delivery) so relatively little for a unit that also contains battery, which needs to be shipped under special-goods categoryQuite fascinating when handheld, as you can both feel & see this current wiggle effect when the burst takes place. (got a specific name this effect, cant recall it)Tested with an AC+DC clamp meter with inrush feature (AC) from a few years back (HT208D) its often sold under names like Kaiweets/Habotest/GVDA etc.. its a 1000A AC/DC clamp meter that costs a fraction of the Fluke variants, at around 35 to 40US incl. VAT & delivery.- it goes without saying that the Amass connector used here below' aint rated for these amps, more like a fraction - and will to an extent bottleneck - but it is very brief pulses, and as long as I don't make too fast continuously burst the heat buildup is tolerable in both the connector and the rigid solid cobber wire when monitor the temp on thermal camera.There are likely way better approaches to doing such tests while having millisecond control over these stacked bursts at hundreds of amps, but for me, it's important that it is small, portable, and easy to store away when not used - alongside being relatively cheap, as it's solely curiosity that drives the interests and a learn a little.preheatburst6ms/mainburst33ms..

author: isso
author_rank: Contributor
timestamp: February 23, 2024, 12:47:26 pm
content: Thanks everyone, I purchased Fluke 355 and tested it and it appears to measure the DC inrush just fine. It looks like the values are a bit lower than expected (20% or so), or maybe the measurement window is small and the current doesn't ramp up as fast...