I also have this machine and noticed the same thing. This is what I found on the Samsung website FAQs:

Why Doesn't The Weight Sensing Message Show Up On Every Load?

Think of it like this: YouÂre cruising along on an interstate at 80 mph, on flat ground. All of a sudden, there is a very steep hill. If you do not accelerate at all when going up the hill, the car will slow drastically. To maintain your speed, you have to press the gas pedal to add more power. Your washing machine is doing basically the same thing. When your washing machine "sees" the need for more power, and the weight sensing message will appear.

LetÂs say you never have to drive up a hill on the interstate, your speed and use of power are pretty much constant, and require very little action on your part. The same thing happens with your washer, if you are doing the same size loads with small variances, there is no need for extra power, and the weight sensing message will not appear.

The weight sensing feature actually measures the amount of amperage the motor is using to turn the drum. You may, or may not, see this message on every cycle. The reason for this is: the machine uses a null amperage value for a normal load. For ease of explanation purposes, letÂs say the null value is 7.5 amps + or  2.5 amps. What that means is a norm load of clothes uses anywhere between 5-10 amps of current to turn the motor.

If you are doing a slightly larger load of clothes it may take 9.0 amps to turn the drum. Because it did not take over 10 amps to turn the drum, the weight sensing message will not appear.

If you are doing a large load of clothes that takes over 10 amps to turn the motor, the washerÂs micom, (computer) will sense that the motor is using more than 10 amps, and it will determine what size the load is by measuring the amperage used to turn the drum. When it has to do this procedure, you will see weight sensing message on the display.

The same holds true for lighter loads.

Thanks Carol, it can be confusing sometimes with all the computer stuff. It does make sence to me for the washer to weight sense the load at every wash, otherwise does it use the same amount of water for say, normal when you may have jeans in it, so that would make the load heavier, so it would seem that it would need more water than with a normal load of just shirts and shorts. I guess it knows what it's doing, it may not be logical to us, but as long as it cleans. I do notice it seems to put in more water on the perm press cycle. Thanks a lot for the info.