LED Current Calculations

I am trying to understand how to calculate current through a series of LED's so they don't get too much and burn out too soon.

Here is the scenario:
I have two arrays of 4 LEDS with an average forward Voltage 1.95v. Using the **broken link removed** I am told to use 68 ohm resistor on each 4 LED Series when supplying 9V and 20 milliamps desired forward current.

After configuring this and powering up the LED's where to place the multimeter probes to confirm the calculation is correct? I noticed that placing the probes between the positive voltage and the resistor yields around 33 milliamps but that must be the total draw of all the LED's? Is my assumption correct? What is best way to validate that there is not too much current going through each LED?

Thanks for the help.

Actually a voltage measurement across the resistor can give you a precise rating for the current that goes through it.
Just use I= V/R where R is the resistor value and V the voltage across it.
In any case since there is a resistor for every four leds the measured current is flowing through the four leds too.

Alex

Read this......
Light Emitting Diodes (LEDs)

Here is my instructions
Led series resistance calculation in 8 steps.................

Calculating an LED resistor value

An LED must have a resistor connected in series to limit the current through the LED, otherwise it will burn out almost instantly.
The resistor value, R is given by:

R = (VS - VL) / I
VS = supply voltage
VL = LED voltage (usually 2V, but 4V for blue and white LEDs)
I = LED current (e.g. 10mA = 0.01A, or 20mA = 0.02A)
Make sure the LED current you choose is less than the maximum permitted and convert the current to amps (A) so the calculation will give the resistor value in ohms ().
To convert mA to A divide the current in mA by 1000 because 1mA = 0.001A.

If the calculated value is not available choose the nearest standard resistor value which is greater, so that the current will be a little less than you chose. In fact you may wish to choose a greater resistor value to reduce the current (to increase battery life for example) but this will make the LED less bright.