testing Laptop power adapter

[darkan9el]

bit of a novice to multimeters but I have a few laptop power adapters that I want to test to see if they are any good.

I actually have two multimeter, a clarkes CDM 10A and I also have a Mastech MAS-343 Auto-range.

On the premise of keeping it as simple as possible I opted for the Clarke and set it to 600v to test the kettle cable, then 20v to test the 19.5v block, the kettle cable gave out a reading of 243v the block connected to the kettle gave a reading of between 19.38v and 19.4v

Does this indicate a faulty charger or is this within an acceptable tolerance?

I have seen videos on such as Youtube that show you how to test stuff but they never appear to show you what is not an acceptable reading, e.g. they showed the charger to give readings of 19.53v indicating a good charger.

Also I can't seem to find a decent book or online reference to using multimeters so if you know of any I'd be grateful if you could let me know.

Forever learning

TIA

 

[PrenticeBoyofDerry]

The power pack should detail the input and output voltage, normally input rating would 100V-240V primary and output for secondary say 19V, if you are reading priamary at around 240V and secondary at around 19V, that suggest the input and output voltages are fine.

Multi-meter link
http://www.clarkeservice.co.uk/manuals/meters/cdm10.pdf

 

[darkan9el]

Hi, you are right re the 240V the secondary should be 19.5V, this is the power adapter for a HP Mini

the printed text says

100-240V~1.1A 50/60Hz

19.5V 2.05A 40W Max

Apologises, should have mentioned that.

 

[PrenticeBoyofDerry]

So that would suggest that there is nothing wrong with the output and input voltages, if you confirm those readings.

 

[darkan9el]

So, its OK to have a 19.5V read 19.4V and be OK? sorry if I appear dumb just trying to understand where you draw the line between a good reading and a bad one.

 

[PrenticeBoyofDerry]

So, its OK to have a 19.5V read 19.4V and be OK? sorry if I appear dumb just trying to understand where you draw the line between a good reading and a bad one.

Allowances of -/+10% is a reasonable figure.

 

[AlanE]

If the label says 19.5volts then really anything between 19 and 20 measured with the average DIY quality test-meter will be OK.

If you look at the test-meter accuracy it will be around 10% +or- one digit. Plus if you are measuring the power supply output without a load (not connected to laptop for example) then the measured voltage might well be a volt or so higher then the value given on the PS case.

 

[darkan9el]

Thank you both for your insight, you have been very helpful., very much appreciated.