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does any one know this panel meter ?, any one can give me better preformens one?
Posted by eevblogfan on 20 Jun, 2011 14:08 -
Hello folk's ,
I am building a 0-30V 0-10A power supply , ( I know too much excessive ... but I can let myself .. )
I need to buy at least 2 panel meter's , (1): for the voltage and (2) :for amperg , and maby I'll buy 4 of them : 1 and 2 for V and A .(3): For CC set ( it will show me the voltage between the non inverting and GND , wich is the max allow able current that will flow ) . And (4) : is the power that the power supply will give me ( V times A ) ,
What I want to know is :
(1) : Does any one know this seller ?
(2) : Does the info that he gives me is correct ? ( 0.1% , 4 ½ digit's display ? , a possibility to modified it to :200mV , 2V , 20V , 200V ? : Ok I need to replace 3 resistors 0.1% and I'll be fine ? , max resolution is 100uA ? /100uV ? )
And all of this he afford me for only 19.50$ ? sounds a little bit lie ? or not ?
Please tell me that I am wrong
link: http://cgi.ebay.com/4-1-2-Blue-LED-DC-2V-Digital-Voltag-Volt-Panel-Meter-/350261421976?pt=LH_DefaultDomain_0&hash=item518d352798#ht_1322wt_932
Right now I don't see any problem with the schema( I'll not upload it here because this isn't the right subject to disscust on .. I'll might upload it in new subject on future ) .
Thank's for the comment's , have a nice day . -
It looks like the components are hand soldered.
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The panel and seller seem reputable, with about 1% irate customers, per his rating. There are other providers of panel meters, at 3.5 digits, its typically as low as $5 and sellers more reputable. Cheap ones are ~ < 1% accuracy. A favorite is the PM128, its sold like hotcakes. Without proper temperature compensation, even using 0.1% resistors will cause drifting with ambient conditions after you calibrate it, so the 0.1% is not going to be easy to achieve. If you just use run of the mill 0.1% you easily achieve 1% accuracy, and thus most mass production meters are as so.
See:
http://www.meterwarehouse.com/Panel_Meters%5CDigital_Panel_Meters%5CDigital_Panel_Meters-Panel_Meters.asp
http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?rf=1&history=xn6qgkrv%7CsubCategoryName%7EPanel%2BMount%252C%2BMeter%5Ecategory%7E4040%5EcategoryName%7Ecat_40%5EprodPage%7E15%5Epage%7ESEARCH%252BNAV%40yhworj45%7Ccategory%7E404010%5EcategoryName%7Ecat_4040%5Eposition%7E1%5Erefine%7E1%5EsubCategoryName%7EPanel%2BMount%252C%2BMeter%2B%252F%2B3.5%2BDigits%5EprodPage%7E15%5Epage%7ESEARCH%252BNAV&sort_field=Price+%28Ascending%29&position=1&refine=1&langId=-1&catalogId=10001&storeId=10001
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I was had plans to buy one of those , but it looks that the maker of it, has as plan to make a fortune of it,
as the price still remains extremely high in comparison with the four digits versions.
The negative part is that also the four digits version is not that well made either.
Instead of getting one of those , I got on eBay an complete Fluke 8010A bench top at less than 30$.
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He has some negative feedback but his answers are priceless, certainly wouldn't buy from him:
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Required to join a forum to get item documentation that proved to be wrong.
Reply by coldfusionx (Apr-15-11 01:08):
No one ask you to join forum to get manual. Manual always open. What a cry BB!!
seller would not communicate Buyer:
Reply by coldfusionx (Feb-25-11 15:34):
Asked inrelevant question (modification). He is one lack of communication.."
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Another note when buying these digital panel meters. Please check if they require an isolated supply voltage or not.
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hello :
Thank u for the comment's , now I need to know ,where is the mains problem with the panel meter , and if someone can give me the solution ,
I think that if I'll buy 0.1% ( or better ) 1/2W divider resistors, and I'll replase the present one's , boom ... the problem is solved ?? or temp stability ( Ppm's ) is the problem here ?
well I don't know , what I am trying to ask is : can I Hack this panel meter to be more relable ( tolerance/temp ) or even more accurate ?
What ever I'll do , I know that this meter has 20,000 max count so the max voltage I am going to messure will be 20V , there for I need to build " auto range meter "( only switch between the different 3 resistors : 10K , 100K , 1M ) just to make my power supply more fancy
, when I'll go lower then 2V I'll be able to see the reading's with 100uV resolution o_o !! and when the voltage go grater then 2V my resolution will be 1mV !! and when the voltage will be grater then 20V my resolution will be 10mV , yea I know , very very fancy , but I work very hard for this power supply 
so I can let myself enjoy from perfect power supply ( well at least right now ) . so for the "auto range " circuit I think to use some zeners , resistors,op-amp ( maby copper one's ) and MOSFET's ( I can get one's as low as 1mohm RDS on . BTW to make this power supply even more professional , I think to use kind of " auto rang " circuit to switch betwin 6 tabs ( or 6 different transformers ) , between each tab we have 5 V , so the max power that we will dissipate is 50W ( maby a little more ) there for I don't need a huge heat sink ( even maby a little CPU one with temp controlled fan ( and of course over temp protection ) . well I don't know when I'll be able to build all of this stuff ( find the transformer/s it's very difficult ) but I know I will , so I might post here the whole proses of building this power supply .
Oh and I saw a "hold" mode ( short 2 pads ) , is this "hold" function is like every multi meter ?
have a nice day !