cheap digital multimeter but it seems unreliable

Thread Starter

Leon_Chan

Joined Sep 11, 2019
81
I bought a cheap digital multimeter but it seems unreliable. However, I do not have another one to compare with.
To start with, I connect a fixed value resistor to it and the reading range is at 200k ohm. As the reading goes up and down, see if you can figure out what is the value of this resistor from the video. Or do I have missed anything important from its manual about its usage?
And show me some videos of how your digital multimeter work. Is it works like that?
https://streamable.com/dt60vm
 

AlbertHall

Joined Jun 4, 2014
10,243
It appears that you have several resistors connected. Make sure that the meter leads connect securely to a single resistor and see what the reading is.
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
81
Have you tried different batteries inside the meter? Any battery that came with the meter may be defective/discharged.
Probably I should try buying a new and better one to see if it is this problem. But consumable battery is expensive when it is not often used.
How often a 9V battery needed to be replaced if it is most often NOT used?

And the multimeter has not indicated that it is out of battery, indicator not displayed.
 
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Thread Starter

Leon_Chan

Joined Sep 11, 2019
81
The resistor is clamped at both end.
If I hold it in the hands, the readings will be much more fluctuating.
Cheap multimeter can only mean it is not very accurate compared to the expensive one. Or it should not be SOLD.
Anyone can show me a video of his multimeter reading?
 

DickCappels

Joined Aug 21, 2008
6,534
You may be acting like an antenna (or capacitor plate more likely) and picking up noise from the environment. The higher the resistance the more likely that is part of the problem.

Along with all of the other tests we are asking for, please hold the probe tips together without touching them and see whether the reading is stable. If not, check for loose things per the posts above and then get a new one.

Some cheap meters are very plenty accurate for most work and can last for years if not abused. The reading jumping around is a bad sign that something is wrong, no need to compare it with another meter.
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
81
The test resistor value in above video is 3K3.

Clamping the two pins together with continuity test show a value of about 024 which is not fluctuating too much.

For a digital multimeter to be useful, it should behave like an analogue one and approach a final value and not in my case fluctuate up and down. I replace the tips with clamps just because it fluctuate up and down while hold in my hand. I have trouble figure out what is the measured value, eg voltage, with this meter.
 

AlbertHall

Joined Jun 4, 2014
10,243
This guy is unimpressed however he does show it giving good readings including on resistance. Actually I think the meter looks better than the reviewer here.
 

DickCappels

Joined Aug 21, 2008
6,534
So far all we have is an offset when a good meter should measure zero.

If you put it into voltage measurement mode what do you get with the two probes connected together, and then how much do you get when measuring a battery?
 

ebeowulf17

Joined Aug 12, 2014
3,274
The test resistor value in above video is 3K3.

Clamping the two pins together with continuity test show a value of about 024 which is not fluctuating too much.
What resistance range did you have selected when you tested the probes pressed together and got the reading around 024? If it was still on the 200k range, that's a HUGE offset! If it was on the lowest range, it wouldn't seem as ridiculous (for a really cheap meter.)

Also, have you tested the alligator clips in the same way, or just the standard probes? It's possible you've got a bad set of alligator clips with intermittent connections in them.

How about retesting the original resistor - but take just one resistor, completely separate it from the rest, and make sure you've got very good contact between probes and resistor (as suggested in posts 2 and 5 previously.) All that other stuff dangling off of the resistor you're testing may have been causing an issue.
It appears that you have several resistors connected. Make sure that the meter leads connect securely to a single resistor and see what the reading is.
Pluck a single resistor out of the bundle and measure it making sure you have a good firm connection contact
 

Audioguru again

Joined Oct 21, 2019
1,767
My Name Brand DMM uses an Energizer 9V alkaline battery that is at least 7 years old. They work perfectly today.
The Energizer 9V alkaline battery has a guaranteed 5 years shelf life. Cheap batteries fail soon the same as anything that is cheap.
 
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