Thanks for the questions David ;)
Yes, you do need a load on the circuit to be able to measure the current - and you need to hook up a string of leads before you measure the current, any less than the required number and you may burn out the LED's. This is not so important with the Meanwell 60-48P drivers as they automatically vary the voltage - the minimum voltage is 24V or 7 LED's.
They method you used to measure the current is quite OK i.e. putting the multi-meter in series with the LED's, but you need to make sure that none of the wires come adrift whilst the power is connected or you can blow the LED's. The major problem is that you need to disconnect a wire every time you want to measure/change the current.
An alternative is to put a 1ohm 5 watt resistor in series with the LED's. A wire wound one like this is best :
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http://www.parts-express.com/images/item_standard/015-1_s.jpg
Now, we will use Ohm's law of I=V/R where I=current, V=voltage and R=resistance. By using a 1 ohm resistor, R=1 which leaves us with I=V. Thus, rather than measure the current we only have to measure the voltage across the resistor which will equate to the current. This resistor can be left in place which means that the current can be easily measured at any time.
When you start, the current should be adjusted as low as possible by turning the variable POT fully counter clockwise - then slowly turn it clockwise until the desired current is achieved. Go slowly as this adjustment is very sensitive and a fraction of a turn can increase the current significantly.
What current should you use??
CREE XP-E's are rated up to 1 amp, with XPG's up to 1.5 amps. However, the CREE datasheet details, included the stated 50,000 hours life, are based on driving them at only 350ma.
There is a trade-off between lumens output, current and heat generated. I plan on providing more information in a future post in the DIY LED build series but the generally accepted compromise is around 750ma.
Hope this helps.