Casella CEL CEL-281 - Manual (Page 38)

able. Equivalent noise levels (L eq ) are also available, calculated with sev-
eral different averaging periods.
3.1.5 Profile
This area calculates and stores level information in the form of time his-
tories. Average sound pressure levels are available calculated with differ-
ent exchange rates Q (including L
eq with Q = 3 and a 1 minute
averaging period). Maximum sound levels with fast or slow time weight-
ings are also available, determined for several different averaging peri-
ods.
3.1.6 Dose
This area calculates and stores noise dose information in terms of per-
centage dose, and projected percentage dose values based on an eight
hour working day, with different exchange rates Q. Results can also be
calculated with various criterion levels and threshold levels.
3.2 Technical Description
Figure 6 is a block diagram of the noise dosimeter, clearly showing the
division into analog and digital sections.
3.2.1 Analog Section
The analog section is similar to a Type 2 sound level meter with its out-
put fed to an analog to digital converter.
The instrument uses a 1 ⁄ 4 " electret microphone capsule installed in a
shock absorbing housing of superior design to earlier types. It can be
mounted close to the wearer's ear using the clip provided and is con-
nected to the instrument by means of a slender integral cable which is
long enough for the instrument to be put in a convenient pocket or
clipped to the wearer's waist-band or belt. In the event of microphone or
cable damage, they can be replaced easily. (Refer to Chapter 7.)
How It Works
Page 30 - CEL-281 Operator's Handbook