Casella CEL-620 Series Integrating Digital Sound Level Meter (Class 2). Casella CEL-620 Series Integrating Digital Sound Level Meter (Class 2) w/Standard Accessories. Casella CEL-620 Series Integrates ANSI Standard Type 1 (Class 2) Digital Sound Level Meter with Standard Accessories. The CEL-620 series of Casella sound analyzers feature powerful DSP processing and a wide measurement range. With the ability to monitor using a single range of 20 to 140 dB, measurements are simplified without the need to change ranges during measurement or pre-determine the correct range. Each 620 series sound analyzer features a large color display and is capable of storing up to 100 measurements for later review or download to a PC. The CEL-630 series of sound analyzers is also available and can be ordered with additional logging capabilities. In addition to providing all the capabilities of a standard sound level meter, the powerful DSP processor of the CEL-620 series stores all sound data simultaneously with each measurement. There are two models and three options available. The difference between the CEL-620 and CEL-621 is that the CEL-621 provides statistical parameters used for environmental measurements. Each model is available in three versions, including the standard 'A' model which monitors all frequencies and time weighting simultaneously, the 'B' model which adds 11 simultaneous octave bands, and the 'C' model which adds 33 simultaneous third octave bands. The CEL-620 and CEL-621 sound analyzers are available with microphones for ANSI type 1 or type 2 accuracy. The CEL-620 can be upgraded to the CEL-621 and/or octave bands added at a later date.