What happens to my child during an ultrasound of the abdomen?

Nothing painful ?!?! Typical ultrasounds are brief & involve a kid on a gurney/bed. The abdomen is uncovered and a glob of clear gel is placed on the abdomen. The technician takes out a probe that looks like an over sized crayon hooked to a long thick wire & machine.The probe is placed on the goo & sends out painless sound waves that bounce off stuff in the belly allowing the machine to locate normal things & problems.