### Author Topic: What do you think of the new Fluke 87 V MAX?  (Read 22053 times)

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#### EEVblog

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #275 on: December 19, 2019, 10:31:33 am »
Worrying about the diode test voltage of a multimeter is like worrying that if you power some 5V logic chips with a 5V, 200A power supply, that the power supply is going to somehow forcing all 200A through those chips and burn them up. It isn't, Ohm's law prevents it. The number "200A" is only the maximum that it might supply if given the chance.
Multimeter diode tests are a current source, not a voltage source. The "voltage" number quoted is only the maximum that it can supply.

Actually, you do have to consider the compliance voltage (as it's called) in some cases. Because the full open compliance voltage, if high enough can potentially damage sensitive unprotected circuits.
Sure it might only be able to supply a mA or two but that might actually be enough to do some damage in some extreme cases.

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#### The Soulman

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #276 on: December 19, 2019, 10:38:45 am »
Worrying about the diode test voltage of a multimeter is like worrying that if you power some 5V logic chips with a 5V, 200A power supply, that the power supply is going to somehow forcing all 200A through those chips and burn them up. It isn't, Ohm's law prevents it. The number "200A" is only the maximum that it might supply if given the chance.
Multimeter diode tests are a current source, not a voltage source. The "voltage" number quoted is only the maximum that it can supply.

Actually, you do have to consider the compliance voltage (as it's called) in some cases. Because the full open compliance voltage, if high enough can potentially damage sensitive unprotected circuits.
Sure it might only be able to supply a mA or two but that might actually be enough to do some damage in some extreme cases.

That and a potentially reversed polarity, don't ask how I know.

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#### Johnboy

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #277 on: December 19, 2019, 06:40:10 pm »
Your Simpson 260 ohms Rx1 is 1.5V at 125mA that does damage semiconductors but works great "out in the wild" where high ohms test-current bites through oxides and organics on electrical connections.

I just measured the Simpson 260-8P's current in continuity mode-- 16.3 mA

Luckily it's not my only meter, although it's been my go-to since it got here.

#### Fungus

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #278 on: December 19, 2019, 07:05:24 pm »
Sure it might only be able to supply a mA or two but that might actually be enough to do some damage in some extreme cases.

There's a topic for a video - see how long it takes for the voltage to drop down. Try to find a component that can be hurt by a Fluke 87V, etc.

I'm betting the settling time is measured in nanoseconds (give or take the capacitance in the probe leads).

#### rsjsouza

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #279 on: December 19, 2019, 07:54:24 pm »

I'm betting the settling time is measured in nanoseconds (give or take the capacitance in the probe leads).

Worrying about the diode test voltage of a multimeter is like worrying that if you power some 5V logic chips with a 5V, 200A power supply, that the power supply is going to somehow forcing all 200A through those chips and burn them up.

That is something I have seen in the past. The absurd low impedance of a voltage source (200A/5V in your example) caused damage exactly due to the extreme slew rate that caused excessive inrush in specific parts of the input voltage regulator. Obviously that was quite difficult to track and, obviously, re-test and correct the problem.
« Last Edit: December 19, 2019, 08:32:28 pm by rsjsouza »
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...

#### Electro Detective

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #280 on: December 20, 2019, 10:15:09 pm »
coin toss gambling 'damage' issue possibility aside, having a 'weaker' meter in this regard so as not to switch stuff on in circuit as DJ pointed out, can come in handy

I'll be running through all my meters when time permits, with fresh and tired batteries, and take notes on all the auto and manual ranges into different resistances and shorts

I've done it before, to see which meters kicked ass in diode mode and Continuity and buzzer speed and LED disco brightness levels

This time I'll scribble it all down on paper scraps, so I don't forget most of it again

Hey yeah, a video of this stuff above would be great if anyone has serious gear, expertise and Youtube channel

and if an 87V can do damage or if the 28-11 (pre-87V MAX rebadged model) is better in that regard
or did Fluke drop the 28-11 diode voltage/current because it runs on 6 volt 4 x AA battery set instead of a single 9 volt battery

Has anyone tried a 28-11 with a 9v battery, or better (safer) still a limited current regulated PSU ramped up SLOWLY  ?
or does it just flash and clap out at 8+ volts, and no performance difference

#### Johnboy

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #281 on: December 21, 2019, 05:07:17 am »
coin toss gambling 'damage' issue possibility aside, having a 'weaker' meter in this regard so as not to switch stuff on in circuit as DJ pointed out, can come in handy

[...]

Hey yeah, a video of this stuff above would be great if anyone has serious gear, expertise and Youtube channel

Seconded. There is some conflicting information on the web. I'm aware that I'm working with outdated equipment, and I'm aware of my own ignorance (for the most part), but it seems that there might be "a trap for young players" out there that should be addressed, even for those with more modern/expensive industrial-grade tools.

#### Per Hansson

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #282 on: December 21, 2019, 09:56:48 am »
and if an 87V can do damage or if the 28-11 (pre-87V MAX rebadged model) is better in that regard
or did Fluke drop the 28-11 diode voltage/current because it runs on 6 volt 4 x AA battery set instead of a single 9 volt battery

Has anyone tried a 28-11 with a 9v battery, or better (safer) still a limited current regulated PSU ramped up SLOWLY  ?
or does it just flash and clap out at 8+ volts, and no performance difference
The 28-II uses 3 x 1.5v AA batteries, so it runs at 4.5v
I have tried it with Energizer Lithium batteries and saw no I'll effect:
Those have a open circuit voltage as high as 1.8v
But now I have had it replaced under warranty and am on the fence about the safety of doing so.
So if anyone knows how the 28-II regulates battery power in depth I'm all ears.
To conform to the listed standards it needs to use the listed batteries on the unit, which are alkaline.

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#### Electro Detective

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #283 on: December 21, 2019, 10:59:25 pm »

..The 28-II uses 3 x 1.5v AA batteries, so it runs at 4.5v..

Thanks for the correction  I assumed it 'logically'?! ran with 4 x AA like some other models in the stable,

I haven't opened mine in ages, actually since I got it to check for crusty batteries and leaks > it just keeps going

which kicks in another question, why not 4 or 6 AA instead of 3 ?
Fluke thinking the user will use the 4th battery in the blister pack to revive the kitchen clock?

So IIRC fresh 1.5v rated alkalines kick at 1.65v (?) so 3 gets one 4.95 to 5 volts tops

3 lithiums at 1.8 volts each will hit 5.4 volts, maybe 5.5?

Surely the meter circuitry has a 10 percent forgiveness factor, seeing as the voltage can only drop over time, current draw and battery shelf life leakage

Anyways, please don't kill an expensive 28-11 to confirm my ghetto math come guesstimate risk taking

« Last Edit: December 21, 2019, 11:02:40 pm by Electro Detective »

#### james_s

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #284 on: December 22, 2019, 03:51:17 am »
My guess is that the digital circuitry is running from 3.3V, so 3x AA batteries is a logical choice. The extra voltage of 4 cells would just get burned up in a linear regulator.

#### Fungus

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #285 on: December 22, 2019, 09:08:37 am »
My guess is that the digital circuitry is running from 3.3V, so 3x AA batteries is a logical choice. The extra voltage of 4 cells would just get burned up in a linear regulator.

Plus they need a lot more space, might not fit inside.

#### Electro Detective

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #286 on: December 22, 2019, 10:11:02 am »

Other Fluke meters with same or smaller dimensions, with more action inside, take 4 x AA (189, 1587)

or 6 x AA (289)

as well as their Process Meters that output current too

Not forgetting the 28-11/87V MAX are an obese tough body version of the 87V,
so space should not be a problem

Some CAD wanking going on during R+D perhaps, to save a dime on plastic molding and a battery terminal?

or a design decision to drop the diode voltage?

or a stuffup to maximise battery runtime, forgetting to check if any negatives

#### tautech

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #287 on: December 22, 2019, 10:12:58 am »
My lowly 15B uses just 2 AA's and they seem to last forever.
Avid Rabid Hobbyist

#### Marco1971

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #288 on: December 22, 2019, 10:54:54 am »

Other Fluke meters with same or smaller dimensions, with more action inside, take 4 x AA (189, 1587)

or 6 x AA (289)

as well as their Process Meters that output current too

Not forgetting the 28-11/87V MAX are an obese tough body version of the 87V,
so space should not be a problem

Some CAD wanking going on during R+D perhaps, to save a dime on plastic molding and a battery terminal?

or a design decision to drop the diode voltage?

or a stuffup to maximise battery runtime, forgetting to check if any negatives

Agree..."stuffup to maximise battery runtime" to meet 800 hours spec. (without backlight on).

#### floobydust

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #289 on: December 22, 2019, 08:03:23 pm »
Only inductor on board the 28II pics is L7 100uH. The kind that break off a pcb after a drop...
Nearby IC's:
U24 TPS77050 5V LDO marking code PCYI
U26 TPS77033 3.3V LDO marking code PCXI
U17 SOT-223 marking code T5 51 not sure what it does
U8 LT1790 2.5V ref (LTPZ)

With the 5V LDO there must be a boost converter and likely why the battery life is extended.

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#### Fungus

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #290 on: December 22, 2019, 09:45:43 pm »
Maybe it has a Batteroo IC in it? This is one place where it could work and the inductor is a really tiny SMD.

#### DiamonDiver

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #291 on: January 30, 2020, 02:02:29 am »
I worked on ships, DMM’s were considered a consumable item, like paper towels.  It’s not using the meter in the rain that kills them, it’s the 800 foot walk in salt spray to change a navigation light or dropping it in the bilge.  Not everyone treats the gear like it’s theirs and if you haven’t worked on ships you wouldn’t understand how tough the marine world can be on gear.

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#### EEVblog

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #292 on: January 30, 2020, 03:00:30 am »
So if anyone knows how the 28-II regulates battery power in depth I'm all ears.
To conform to the listed standards it needs to use the listed batteries on the unit, which are alkaline.

A hires teardown photo might reveal a lot.
I could probably go a few minutes down the road to Fluke HQ oz and get one, but I couldn't be arsed

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#### srjaynes49

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##### Re: What do you think of the new Fluke 87 V MAX?
« Reply #293 on: September 19, 2020, 07:16:38 am »
I’m willing to bet the extra drop durability of the 87-V Max comes from the thickness of the holster. I’m going to do some precise measurements of the actual meters and their holsters and report back.