Author Topic: Thinking of buying a multimeter.  (Read 23986 times)

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Offline vladdrake

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Re: Thinking of buying a multimeter.
« Reply #50 on: July 28, 2014, 05:02:56 am »
I really thank you for the good explanation about what is a bar graph and what is it for.

So which one of the three multimeters do you think is the best?
 

Offline torr032

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Re: Thinking of buying a multimeter.
« Reply #51 on: July 28, 2014, 11:26:28 am »
I really thank you for the good explanation about what is a bar graph and what is it for.

So which one of the three multimeters do you think is the best?

When I choose to buy some product, I always go to the most popular trading site in China, taobao.com and there I apply the best selling filter. If the chinese buy something the most in the land where competition is greater than in other countries then it must be good. Among  better quality DMM's ut61E is the clear winner.
 

Offline idpromnut

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Re: Thinking of buying a multimeter.
« Reply #52 on: July 28, 2014, 12:58:20 pm »
This might come up a bit late, but the UNI-T 136C (with temperature) is fairly accurate, reasonably built and a decent "dicking around on the bench" meter. At CAD22$ shipped, it was a great temperature meter with the extra DMM features thrown in ;)
 

Offline larry42

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Re: Thinking of buying a multimeter.
« Reply #53 on: July 31, 2014, 10:22:33 am »
You're doing something wrong.

A LED rated for 22mA (normal max, not Abs. Max) will not blow up at 22.1mA, unless it's faulty or other things are happening (such as an oscillating supply, current hogging etc) - are you driving these LEDs in series or parallel?

You're doing something wrong, or your designing something wrong if you need more than 5% accuracy in current measurements for LEDs.

Hey there LaurenceW! Thank you for the imput! I don't need it to 350.05 but i did need it to 350.5 at the time. Or to be precise at 350.4. Why? Because i had 16 LED's with a maximum tolerance of 22mA and i wanted to run them at their peek performance without blowing them out. So i settled for 21.9mA for each, totaling a 350.4 mA draw. At least that was my logic. Could i have powered them at 21 mA? sure! 20? Sure! But i wanted absolute peek performance without killing them. So i decided at 21.9 mA. That lead me to a constant current source of 350.4 mA. And trust me, at even 23 mA per LED, those LED's burned out. As to the design, that's what i found during a quick search on google. Not my design, don't even know if it's any good. Was just a proof of concept, because somebody asked if i needed 0.01% precision on resistors. He believed i meant resistors when i mentioned of powering LEDs. Anyway, let's not drift offtopic. :) Thanks yet again to everyone for the help. I'm now just waiting for the next paycheck to buy this puppy! :D
If you have an animated GIF in your avatar or signature then I reserve the right to think you're a dolt.
 

Offline larry42

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Re: Thinking of buying a multimeter.
« Reply #54 on: July 31, 2014, 10:24:08 am »
When I choose to buy some product, I always go to the most popular trading site in China, taobao.com and there I apply the best selling filter. If the chinese buy something the most in the land where competition is greater than in other countries then it must be good. Among  better quality DMM's ut61E is the clear winner.

Of course that is an unstable feedback system - imagine if all the purchasers start to do that - rail to rail immediately... :)
If you have an animated GIF in your avatar or signature then I reserve the right to think you're a dolt.
 

Offline onlooker

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Re: Thinking of buying a multimeter.
« Reply #55 on: July 31, 2014, 12:54:09 pm »
From adrianf88's posts, I guess he is simply parallel all his 16 LEDs, which is,in general, a big no no.

Such setup will explain why some LEDs will be burnt out earlier than others since as others had already pointed out LEDs are not really made equal even in the same batch.

In fact, once some are gone, the others will be destroyed too due to the same CC  is distributed to less number of LEDs.
 

Offline torr032

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Re: Thinking of buying a multimeter.
« Reply #56 on: August 01, 2014, 03:45:40 pm »
When I choose to buy some product, I always go to the most popular trading site in China, taobao.com and there I apply the best selling filter. If the chinese buy something the most in the land where competition is greater than in other countries then it must be good. Among  better quality DMM's ut61E is the clear winner.

Of course that is an unstable feedback system - imagine if all the purchasers start to do that - rail to rail immediately... :)

Well I use it pretty often. Sometimes I buy item directly on taobao, sometimes I find the same on ebay. It works quite well and on taobao you are able to see buyers comments. Together with comments on  amazon and with a little forums search you are able to distinct fake versus real ones reviews and get a picture of the product.
 


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