Ok. So I've had a lifetime of problems trying to have an ohm-meter at the right time. I've never had one I think.

Right now I have this 10$ astroAI multimeter, which was very highly reviewed. It measures lower value resistors ok, although always a bit low.

It seems to measure volts fine.

I have some battery resistance testers, these are always reading lower values (like , below 20 ohms) with apparent accuracy, but I was just doing a lab#1 I got from a book off amazon, and I measured with my 10$ multimeter to verify the 1Meg resistor, it showed below 500k . I was like oh man, my resistor is no good, these cheap resistors ... but after spending some time trying to figure out how I could possibly accurately measure ohms, I figured out my fnirsi transistor tester does it if you can put the component into the slots, and I measured it to very close to 1Meg with that device. This means most likely that my multimeter is always low, (which it is) but along a curve, which means that at higher resistance values it is extremely inaccurate.

I don't know all that much about how multimeters work, I am to understand the ohm-meter is quite fragile (like, if you use it on a live circuit you can damage it). I do not believe I have used it on a live circuit but perhaps I did juice it clicking past it? perhaps it was just not very good out of the box.

What is my best course of action to achieve the ability to accurately measure resistance? I've had like 6 cheap multimeters, none of them measure ohms because I broke them all. right now it looks like this transistor tester is all I have that will work. (technically, I am only sure I broke 1 of these cheap multimeters, and NONE of them ever measured the value of the resistor, I recall they all were low to the best of my memory, although for most of the time they were only ever used for voltage).

I know people will say "get a fluke multimeter" but if I am 6 for 6 in breaking them myself, which is entirely possible, I do not want to break an expensive one, and be 7 for 7. I don't mind using the transistor tester for now, it's just some components in some experiments in a book, But I feel like I should know more. Is ohms known to be something that is always inaccurate with multimeters? Are they always very low with high values like 1Meg when the multimeter is cheap? I feel like this is not data that is easy to find, unless people are going to buy loads of multimeters and do comprehensive testing like people do with pocket knives on youtube, I will not know what to expect from multimeters.

 

There's not much you can reasonably expect from a $10 multimeter, either in terms of quality or durability.

If you step up into the $20 to $30 range, you will probably find a much higher level of both.

I've had my Micronta (Radio Shack) meters for over 40 years, including some very heavy abuse, and they are still functioning (though on one the AC voltage functions don't work any more).

I don't know what you are actually measuring when you stick a resistor into a transistor tester's slots. It's almost certainly not resistance.

 

To measure resistance a multimeter sends a known current through the resistor and measures and displays the voltage. R = V/I. For the 200 ohm range this is probably 1.0mA but for higher ranges it could be as low as 1uA. In a cheap meter the impedance of the meter itself will be seen in parallel with the resistor you are trying to measure and there could probably be a parallel high resistance path, for example the PCB itself. On the high range you may be able to see this if the meter shows a resistor value with the probes in the air.

How are you actually breaking them? Always set to a higher range than you expect to measure before connecting the probes and don’t put a voltage across the probes when the meter is on a current range.

After breaking 6 you should by now have enough experience to spend 6 x $10 on a better instrument!

 

@tsmspace You mentioned battery resistance. You cannot measure battery resistance with a multimeter. If you are doing this, it is no wonder that you are killing your multimeters.

 

Mr Chips is totally correct!!
Finding a battery internal resistance requires measuring two quantities at the same time, and then doing some math. What you get, after the math, is a measure of the effective battery internal resistance AT A SPECIFIC CURRENT FLOW!

To determine a battery effective internal resistance, first, the battery voltage with no load is measured, NEXT, a load is connected to draw an accurately measured current, and the battery terminal voltage is measured again while that current is flowing. After that, the battery voltage drop can be calculated, and the battery resistance equals the voltage drop divided by the battery current. ( R= V/I ).

 

Is you meter auto- range or manual? If manual, you might be measuring on the wrong range.

 

There's not much you can reasonably expect from a $10 multimeter, either in terms of quality or durability.

If you step up into the $20 to $30 range, you will probably find a much higher level of both.

I've had my Micronta (Radio Shack) meters for over 40 years, including some very heavy abuse, and they are still functioning (though on one the AC voltage functions don't work any more).

I don't know what you are actually measuring when you stick a resistor into a transistor tester's slots. It's almost certainly not resistance.

it's a transistor tester, but it tests transistors, diodes, resistance, inductance, and capacitance. It automatically detects which one it is testing and then gives the appropriate value. It's not always right, however. If you test a transformer it just tests it as a resistor instead of an inductor. But for everything else I've put in there it's detected it correctly.

 

@tsmspace You mentioned battery resistance. You cannot measure battery resistance with a multimeter. If you are doing this, it is no wonder that you are killing your multimeters.

I'm not measuring battery resistance with a normal multimeter, it's a "battery resistance tester", with a 4-lead probe set. I have two, one is fnirsi and the other is the "rc3563". They are very accurate at measuring resistors, but only below a certain value, which is very low and not useful for most resistors. Batteries typically have a very low resistance so they only measure up to like 200Ohms max.

 

Is you meter auto- range or manual? If manual, you might be measuring on the wrong range.

I do this all the time, measure one out of range, and figure it out. I wonder if this actually causes them to break, I'm careful not to test charged circuits.

 

To measure resistance a multimeter sends a known current through the resistor and measures and displays the voltage. R = V/I. For the 200 ohm range this is probably 1.0mA but for higher ranges it could be as low as 1uA. In a cheap meter the impedance of the meter itself will be seen in parallel with the resistor you are trying to measure and there could probably be a parallel high resistance path, for example the PCB itself. On the high range you may be able to see this if the meter shows a resistor value with the probes in the air.

How are you actually breaking them? Always set to a higher range than you expect to measure before connecting the probes and don’t put a voltage across the probes when the meter is on a current range.

After breaking 6 you should by now have enough experience to spend 6 x $10 on a better instrument!

Well, some of them I'm sure I broke them by measuring a charged circuit. The older ones, I think this is what happened. At some point I would have been trying to troubleshoot something or other and just thought that was the plan. But, I bought more, and am careful not to do that, but at the moment I only have one that even gives a stable value, and it's inaccurate by an amount that correlates to the resistance measured. For lower values it's out by less than 10%, but for 1Meg I measured less than 500k, and then as I said I did measure it as 1 meg in the "Fnirsi LCR-P1" which makes me think this device is working properly, while the multimeter is not.

Yes well as for buying a nicer meter, I don't know people only really say good things about >300$ meters. There aren't comprehensive reviews like there are with things like graphics cards, so at the moment I'm just not sure what would happen if I spent 60$ on a meter. 60$ is more for some than others, and I'm on that it's more end of the spectrum.

 

Yes well as for buying a nicer meter, I don't know people only really say good things about >300$ meters. There aren't comprehensive reviews like there are with things like graphics cards, so at the moment I'm just not sure what would happen if I spent 60$ on a meter. 60$ is more for some than others, and I'm on that it's more end of the spectrum.

It hugely depends on how important it is for you to have really accurate readings. Reading 500K instead of 1.0M is poor by any standards but do you need an exact result for a special reason? These days, I'd look online for something less than say $50 which has good buyer feedback and the ranges you want.

 

I don't know all that much about how multimeters work, I am to understand the ohm-meter is quite fragile (like, if you use it on a live circuit you can damage it). I do not believe I have used it on a live circuit but perhaps I did juice it clicking past it?

I'm careful not to test charged circuits.

Well, some of them I'm sure I broke them by measuring a charged circuit.

It sounds like you don't know how to use a multimeter properly. Whether the circuit is "charged" or not, in general, you can't measure resistance in-circuit.

Is this what you were doing when you measured the 1M resistor? Even a cheap DVM shouldn't be off by 50%.

You mention not understanding how multimeters work. You can measure voltages in-circuit because the meter should have a high enough input resistance to not perturb the reading. For resistance a known current is delivered to the resistance; the amount being determined by the range. That's why you shouldn't try to measure resistance in-circuit; you'll be powering things up and the reading will depend on what is in parallel with what you're trying to measure.

 

My FLUKE model 77 meter did a great job on resistance. But I traded it for a good dual band mobile radio, and now I AM suffering regrets on that deal.
Resistance readings on an inexpensive analog meter are often only close on the lower quarter of the ohms scale, and those meters CERTAINLY DO NOT use any regulated current source for checking resistance. That is why they all have an "Ohms Zero" adjustment. Even my SIMPSON 260 analog meter is less accurate to read on the higher end of the resistance scale.
AND, using any analog meter to measure resistance on a live circuit WILL PROBABLY CAUSE SERIOUS DAMAGE!

 

if target resistance is not powered (separate resistor) DMM configured to measure resistance can be used directly.
but in case of battery, internal resistance cannot be separated from battery. so doing above will just destroy DMM. higher grade DMMs may have better protection and could survive such abuse.

if you want to measure internal battery resistance using DMM, you need two DMMs, one configured to measure voltage and one to measure current.
notes:
1. you could use single DMM at the expense of reduced accuracy.
2. this will tell you battery resistance for one load. but since internal battery resistance is not linear, for complete answer would be to repeat this for various loads and then plot the curve through all calculated points.

 

Yes well as for buying a nicer meter, I don't know people only really say good things about >300$ meters. There aren't comprehensive reviews like there are with things like graphics cards, so at the moment I'm just not sure what would happen if I spent 60$ on a meter. 60$ is more for some than others, and I'm on that it's more end of the spectrum.

I use this multimeter (OWON XDM1041, $76.48):

 

It sounds like you don't know how to use a multimeter properly. Whether the circuit is "charged" or not, in general, you can't measure resistance in-circuit.

Is this what you were doing when you measured the 1M resistor? Even a cheap DVM shouldn't be off by 50%.

You mention not understanding how multimeters work. You can measure voltages in-circuit because the meter should have a high enough input resistance to not perturb the reading. For resistance a known current is delivered to the resistance; the amount being determined by the range. That's why you shouldn't try to measure resistance in-circuit; you'll be powering things up and the reading will depend on what is in parallel with what you're trying to measure.

Well I would usually be looking for a short or open , so i would have been just seeing if there WAS a reading. obviously this is some hobby kind of activity, which means it took place over many years, i'm talking about things I've done over the decades.

 

It hugely depends on how important it is for you to have really accurate readings. Reading 500K instead of 1.0M is poor by any standards but do you need an exact result for a special reason? These days, I'd look online for something less than say $50 which has good buyer feedback and the ranges you want.

well that IS what I did to end up with the astroAI one. It came highly reviewed from the reviews available, although they all kind of read like ads. It's not like knife reviews where you get joe x smashing a log then a brick until it breaks. You just get a little paragraph that says "i like it" or "it was hard".

I'm trying to learn electronics so to speak, like, get some example experiment and then perform it. I do want reliable test equipment that will perform these experiments, mostly things like what sorts of electronics one might have at home. I'm interested in radios, amps, computers, microcontrollers, and robotics.

 

I'm trying to learn electronics so to speak, like, get some example experiment and then perform it. I do want reliable test equipment that will perform these experiments, mostly things like what sorts of electronics one might have at home. I'm interested in radios, amps, computers, microcontrollers, and robotics.

If you really want to learn electronics how about building your own multi "meter" - quotes because when I didn't have one I built a circuit with potentiometer and comparator driving LEDs which assumed the pot resistance was linear so I could compare an input voltage to a potentiometer wiper voltage to watch the position where one LED went out and the other came on. Point being, although a multimeter is probably your first and most important measuring instrument, you can probably get by without it if you have to. A bridge circuit using know resistor values to measure resistance for example

 

what to expect from multimeters.

they won't measure any resistance accurately enough

i have double DVM850BL --and-- 2 other alike = all 4 have same measurement ranges and they have different displays at all of theses ranges - however 1 of them compares better than others to a KYORITSU voltage ranges + the 5-th cheapo DMM has a calibration pot inside so i matched it also to a japanese thing at its voltage range (which might have impacted the other ranges for worse ?)

i got also an ancient comparative bridge resistance meter which is most accurate but not error free
i had a set of EXCEL tables** that had statistics over a box of resistors by which** i was able to estimate the apx precision of each of my DMM

even if you set up a speciffic resistance test rig - then all values that can have an error do have 'em !!!
▼
► your option is -- to have few...enough expensive calibrated resistors --and/or-- voltage references --and-- you work your way out based on them

DMM is basically a "black box" when it comes to precision