Looking for a multimeter with these functions

[nctnico]

While many of you engineers can argue about my lack of knowledge how electronics work (which i will not deny i have no clue how they work) it all comes down to one problem which is:
99.9% of all meters on this planet will measure 1.2K while 0.1% will measure 300ohms or if leads are reversed, 2.5k but no where near 1.2k.

My guess is that you are trying to measure in-circuit then. In that case you need to understand that all chips have transistors, MOSFETs, ESD diodes (=semiconductors) in them which cause resistance readings to depend on the measurement direction and measurement current. There is no fixed input resistance when semiconductors are involved. IMHO this is a good thing. I have used this property to find failed chips on numerous occasions by measuring resistance in both polarities and between ground and pin and supply and pin. On pins with similar functions you should measure similar resistance values when measured using the same polarity.

I think looking for a DMM with a limited open voltage is a good thing as modern semiconductors can easely be damaged by high voltages. Unfortunately many DMMs have rather high open voltages like 8V which is way too much. I like the Vichy 8145 bench DMM I have for that reason, it measures diodes using 3.3V which is generally speaking safe.

[TimFox]

A digital ohmmeter usually applies a fixed current to the resistor under test, but limits the voltage compliance to avoid semiconductor damage.
With 1 mA constant current, a 2.0 kohm resistor will measure 2.0 V and be displayed as 2.0 kohm.

[tonycstech]

I am trying to measure 1.8v rail on any graphics card.
Uni-T 181 is what i was looking at the other day but i think its a fluke 289 knockoff so i expect it to act the same.
If not, it would be nice but at the same time, it still does not have live trend view.

[tautech]

I am trying to measure 1.8v rail on any graphics card.
Uni-T 181 is what i was looking at the other day but i think its a fluke 289 knockoff so i expect it to act the same.
If not, it would be nice but at the same time, it still does not have live trend view.

V ?
A ?
R ?

[tonycstech]

what ?

[tooki]

He’s asking what value you want to measure. And probably why.

Other than identifying a gross short circuit on a power rail, its resistance is meaningless.

It isn’t clear to me (and likely everyone else here) what it is you’re trying to accomplish. Like, what is it you think you learn from a resistance measurement of a circuit with non-ohmic components? (I am not asking this to be sarcastic or rhetorical, I am genuinely curious as to what insight you gain, or wish to gain, from such a measurement.)

Correct me if I’m wrong, but I think you think that the numbers you get are in some way inherently meaningful. But they aren’t. The only thing you can do with them is compare them to other numbers from a similar meter. That is because the numbers are only “true” within the exact test conditions created by that meter. A meter that creates different test conditions will create totally different numbers with an active circuit. Neither one is more or less correct than the other, because they’re both specious.

Testing in-circuit is always fraught with peril. You really need to know what you’re doing so you can know which results are valid and which aren’t — and when you have no choice but to remove a component from the circuit to measure it. Just today, I desoldered a few resistor networks and a transformer from a board in order to determine the resistor networks’ topology and the transformer specs. No way to do it in-circuit.

[tonycstech]

What value i want to measure ?
The resistance value of a1.8v circuit on an Nvidia GPU.

What am i trying to accomplish ?
Consistent reading with 99% of all hand held multimeters to match with FLUKE

Values are meaningless ?
I have to disagree. After doing so many of these i can tell what the problem is just by looking at the value.

Testing in circuit is always.......?
yeah, except that when i get the same reading using anything buyt FLUKE and bench meters, begs the question. Why not design your meter to get the same reading ?

Other than that, FLUKE replied to me saying they "do not offer" firmware modifications.

My argument is simple. 99% of all meters will give me one value while 1% will give me another.
its a simple majority rule.

I do not agree with the democracy in this regard because majority could be a bunch of idiots and there has to be a balance so the balance is: let me adjust voltage/current of the meter so i can get the same reading as other meters get.
But we all know thats not going to happen so there is no point to continue this topic.
Someone please lock it.

[nctnico]

What value i want to measure ?
The resistance value of a1.8v circuit on an Nvidia GPU.

What am i trying to accomplish ?
Consistent reading with 99% of all hand held multimeters to match with FLUKE

That is not going to happen due to differences in measurement currents and how the multimeters are constructed internally. The open voltage on various meters is different and some meters may have a true current source while others may have a simple series resistor to limit the measurement current (depending on range). Both methods will yield valid results when a true resistor is connected to the meter. However, when measuring in-circuit with semiconductors involved, you will get different readings between meters.

[KungFuJosh]

I do not agree with the democracy in this regard because majority could be a bunch of idiots and there has to be a balance so the balance is: let me adjust voltage/current of the meter so i can get the same reading as other meters get.
But we all know thats not going to happen so there is no point to continue this topic.
Someone please lock it.

Yikes. That's inherently flawed thinking. As others have said, those readings are meaningless.

The only time your in-circuit measurements have meaning is if you're comparing a known good DUT vs a faulty DUT (both identical circuits), under the same measuring circumstances. Then you can compare the values and ponder why the discrepancies. Without that specific comparison, you would need a schematic with in-circuit values for every device, and that doesn't usually exist.

Altering a DMM as you suggested is called adjustment. Adjustments are made with a calibrated machine, usually specifically made for this purpose. Arbitrarily adjusting a DMM based on irrelevant noise will only guaranty degrading your DMM.

[tonycstech]

i fixed nearly 100% of all devices that come to me with my inherently flawed thinking. Lucky or maybe i see what most people dont ?
I dont even have autism to be this smart  if anything, i see my self as plain stupid 

I knew this wouldn't go anywhere since the very 1st reply.
Why am i still here ?
For the same reason i have high success repair rate. Just cant let it go.

[J-R]

The graphics cards are going to have similar operating principles and similar PCB layouts.  So obviously you are going to learn what to look for, even if your method is flawed from a technical standpoint.  It's fine to go that route if you've got work to do.  But from a "right" and "wrong" perspective, you're just flat out wrong and the more you double-down on your position, the more foolish you look unfortunately.

You already know how to inject voltage into various parts of the circuit to look for shorted components.  The same principle applies with my suggestion to use a bench power supply set for the values you want.

[TimFox]

i fixed nearly 100% of all devices that come to me with my inherently flawed thinking. Lucky or maybe i see what most people dont ?
I dont even have autism to be this smart  if anything, i see my self as plain stupid 

I knew this wouldn't go anywhere since the very 1st reply.
Why am i still here ?
For the same reason i have high success repair rate. Just cant let it go.

Even if you don’t understand the circuit you are testing, nor how your different instruments work, nor what “resistance” actually means, it is allowed to write a test procedure, based on your empirical observation, to use a specific instrument and specific connections, with the allowed range of displayed values, even if the actual measurement is not understood.
However, if your instrument is no longer available some years hence, someone will have to start over.
That’s why we are trying to educate you despite your stubbornness.

[tonycstech]

Correct my theory if am wrong (am sure i am)
A: multimeter uses 2v to measure resistance and gets 300ohms because parts of the circuit it measures gets enough current from those 2v to actually do something with it, such as pass it alone down the line or the other way around. This make sense considering typical voltage any transistor gates is anywhere from 1-3v and the fact that there are semi conductors just complicates this process even more.
B: multimeter uses 0.5v to measure resistance and gets 1.2k because none of the parts of a circuit get enough current to do anything with the 0.5v and therefore resisting the current flow much less giving you higher value in Kohm range.

Thats what i think is happening here.
For that reason, i want to lower the voltage and limit the current to get the same results of a chinese meter.
Cant do it. No one can. Whats the point of this conversation ? No point.

[TimFox]

Correct my theory if am wrong (am sure i am)
A: multimeter uses 2v to measure resistance and gets 300ohms because parts of the circuit it measures gets enough current from those 2v to actually do something with it, such as pass it alone down the line or the other way around. This make sense considering typical voltage any transistor gates is anywhere from 1-3v and the fact that there are semi conductors just complicates this process even more.
B: multimeter uses 0.5v to measure resistance and gets 1.2k because none of the parts of a circuit get enough current to do anything with the 0.5v and therefore resisting the current flow much less giving you higher value in Kohm range.

Thats what i think is happening here.
For that reason, i want to lower the voltage and limit the current to get the same results of a chinese meter.
Cant do it. No one can. Whats the point of this conversation ? No point.

Now you are acting like a stubborn jerk.  In my first reply to your other post, I told you exactly how to lower the voltage and measure the apparent resistance.
https://www.eevblog.com/forum/testgear/lower-voltage-for-resistance-measurement-for-fluke-289/msg5658253/#msg5658253

There is a type of device that would probably work for you.  It is programmable, very flexible, and rather expensive:  technical name "source-measure unit".
Examples:https://www.tek.com/en/products/keithley/source-measure-units 
A field engineer from Keithley could probably show you how to program it for your application.
Used, they run from roughly $3500 to $6000 USD

[ArcticGeek]

I don't know if this will work for your measurement or not, but the OLD Beckman Tech 3XX meters (Tech 310,320,330) have a very low in circuit voltage of only 200mV when measuring resistance.  It's an oldie but a goodie, and its the lowest voltage I've ever seen on a multimeter.  The meter is not auto-ranging like today's  multimeters (Fluke or otherwise), but its a low enough voltage it won't turn on silicon junctions.

[joeqsmith]

Please all read his other threads before replying:

https://www.eevblog.com/forum/testgear/lower-voltage-for-resistance-measurement-for-fluke-289/msg5658247/#msg5658247

https://www.eevblog.com/forum/testgear/fluke-289-no-live-trend/new/#new

I had watched a recent video Dave made on a returned meter with a similar problem with OP's. 

[KungFuJosh]

For that reason, i want to lower the voltage and limit the current to get the same results of a chinese meter.
Cant do it. No one can. Whats the point of this conversation ? No point.

The Shannon ST42 LCR Tweezers have adjustable voltages and frequencies, which might work in your situation.

Good LCRs typically allow for adjustment of test voltage. As I said previously, you need to know the correct tools for the job, and how to use them, rather than trying to force an apple to be an orange.

The R (in LCR) stands for Resistance, and the ST42 can do Rs, Rp, Z, ESR, and Rdc. The ST42 voltage is rated at maximum 1Vpp, which means about 350mVrms. Test frequencies from 100Hz to 10kHz.


ETA: Since what you really need is an LCR, if you also need graphing, you'll need to spend more. Either a bench LCR with ethernet, or a HH LCR with BT. But you can also use some LCRs with TestController software, which will allow all sorts of graphing.

[tonycstech]

I understand the problem measuring resistance on a live circuit, i never said thats what i was doing.
I also understand measuring 10k resistor in circuit will give reading effected by other components and not 10k.
The reply count has gotten out of control so people start to make way too many assumptions so as a reminder, most multimeters will measure OK while fluke wont.
I am simply looking for a meter that has what i need that will measure resistances same way other Chinese no name junk does. It seems to be consistent across most of the chinese brands while premium products have different readings.

This wasnt even about the reading, it was about features.
At this point i give up on the search and shift focus to FLUKE firmware hack because there is no other way to fix it.

[joeqsmith]

I understand the problem measuring resistance on a live circuit, i never said thats what i was doing.

I never suggested you were measuring a live circuit but rather that your are just ignorant when it comes to their use.   

I doubt you would ever read this, but for others, this is a book on the basics of in-circuit testing.
https://www.ietlabs.com/pdf/Handbooks/Introduction%20to%20In-Circuit%20Testing.pdf

[csuhi17]

Have you asked Fluke about your problem?  It is possible that you will get an answer sooner.

[BillyO]

live(or slightly delayed) data graph for voltage and resistances
Uses 3v to measure diode
uses 2v to measure resistance
can read as low as 0.01 ohm

and is decent overall ?

Have a look at the FNIRSI DMT-99.  It seems to come close to what you want.

Has data graph
Uses 4V to measure diodes (a bit higher than you wanted, but not ridiculous)
Uses 0.61V to measure ohms  (will not be affected by most semiconductors in circuit).
Can read to 0.01 ohm  0.1Ω
Is very solidly built.

It's also compact, light and cheap.

Edit: So, I guess it does not meet your specs after all.  I got the ohms range wrong before.

[Antonio90]

Hello tonycstech.
The UT181 will put a max compliance voltage of 1.2 in the kOhm range and upwards, below that is 3.3V. The graphing is not live though, you have to record and then plot, unless you use the included IR interface.
The Metrix MTX 3282 (and I guess the rest of the series) has an around 1.2V max compliance voltage, which drops pretty quickly. It is discontinued, and a bit quirky in a few regards, but you might find one second hand. It does live graphing.
2N3055 recommended, in the third reply, a currently  produced model. Also has live graphing but it is quite expensive.

Also, the Ohms function in DMMs is designed to work with ohmic circuits, and intends to give results relative to Ohm's law. If you are using it for a different purpose and it doesn't work, it doesn't mean there is a design flaw, or that the meter is crap, you are just using it for a different purpose. The fact that some of them work is just a nice bonus with some DMMs. That's why you are getting flak.

I think what you are trying to measure is a circuit signature (not sure about that name). There are expensive curve tracers for automated test setups, which compare the traces of products with a known good sample in the production line.
In this case, that is kind of what you are doing, identifying problems with controlled test conditions by comparing with a known good sample. You might be able to use the ohms function, but the tool for this is not necessarily an ohm meter.
You might be better off modifying one of the "shorty" circuits, or using an Analog Discovery.

EDIT: The diode test voltage of both the Metrix and the UT181A is ~3.1V.

[nctnico]

live(or slightly delayed) data graph for voltage and resistances
Uses 3v to measure diode
uses 2v to measure resistance
can read as low as 0.01 ohm
and is decent overall ?

Have a look at the FNIRSI DMT-99.  It seems to come close to what you want.

Has data graph
Uses 4V to measure diodes (a bit higher than you wanted, but not ridiculous)
Uses 0.61V to measure ohms  (will not be affected by most semiconductors in circuit).
Can read to 0.01 ohm
Is very solidly built.

It's also compact, light and cheap.

But the specifications are ridiculously bad. Like 1.5% accuracy on resistance measurements. It has 10000 counts (0 through 9999) but it could just as well have 100 counts and still show the result with the same accuracy.

[BillyO]

But the specifications are ridiculously bad. Like 1.5% accuracy on resistance measurements. It has 10000 counts (0 through 9999) but it could just as well have 100 counts and still show the result with the same accuracy.

Well, he seems to hate better meters.

Another nice feature of is that it autoranges shockingly fast.  Even in auto mode it will determine what parameter you are measuring and provide a value 3 times faster than the Brymen 786, which is already switched to the correct mode (Ω for instance).

I love a 6.5 digit meter with 0.01% accuracy on ohms as much as the next guy, but repair work is not like R & D or experimentation.   Insane accuracy is not key.  You are mostly trying to see if a component has failed rather than whether a 1% resistor is 0.01% out of tolerance.

Also, try not to cherry pick or use lies of omission when you're denigrating something.  That's an untrustworthy politician's move because he thinks no one will fact check him (see Donny Trump as an example).  That 1.5% tolerance you tried to pass of as the entire story is only for the 99.99MΩ range.  Everywhere else in Ω it is 0.5%  which is fine for an inexpensive meter like this.

[nctnico]

It says right here that the 1.5% is for the entire Ohm range:
https://www.toolworld.in/storage/media/product/technical_documents/DMT-99%20Multimeter.pdf

Since most circuits use 1% resistors nowadays, I'd like to have a meter with more accuracy than the components which isn't hard to achieve. I do hope you agree with the fact the DMT-99 is showing way too much digits versus its accuracy. I hope you also see that measuring 0.01 Ohm is not going to happen with a relatively simple, 2 wire DMM. Heck, most 6.5 digit DMMs will have trouble doing that even though these typically have 4 wire connections. Your best bet for measuring low resistance values is likely the Keithley DMM6500 which has a 1 Ohm range versus the usual >= 200 Ohm range being the lowest range for resistance measurements on DMMs.