The Doppler Effect Flow meter uses reflected ultrasonic sound waves to measure the velocity of particles in the fluid. By measuring the frequency shift between the ultrasonic frequency source, the fluid carrier, and the receiver, the relative fluid velocity is measured.
How long it took to freeze will have a bearing on it, too. If the ground beef was 3 days old when frozen, you might try cooking it from frozen. If it was freshly ground when frozen, the thawed meat will likely be good for 2 days. Once thawed, the ground meat should be used within a day or two. Ground meat spoils quickly since grinding the meat mixes bacteria throughout.
Label the beef when you refreeze it, indicating how long it was thawed. The safe lifespan of ground beef is three days or less in your refrigerator, and every day thawed counts against that total.