Casella CEL CEL-450 - Manual (Page 16)

run timing facilities. These allow it to operate with user set delayed start
and stop times, and to store period results taken at regular intervals.
1.8 Instrument Power Supplies
All of these instruments are powered by a set of four standard AA size
batteries in a compartment in the back of the instrument case, and it is
recommended that alkaline IEC Type LR6 be used. Rechargeable
batteries can also be employed, but some types may give a shorter
operating life. Zinc carbon batteries are NOT recommended.
If there is doubt whether the batteries will be able to power the
instrument for the start and stop times set, or when measurements are
needed over long periods, the instrument can be powered directly from
an external 12 V DC supply without the need to remove the internal
batteries.
DAMAGE to the instrument will occur if an
external power supply exceeds 14 V DC. The
nominal external supply is 12 V DC.
External power for the instrument is supplied via a 2.1 mm co-axial 2-line
D.C. connector in the bottom of the instrument case. Terminal polarity is
+12 V DC on the tip and 0 V DC ground on the sleeve.
A Casella CEL Universal Power Supply (-PC18) may be used to
power the instruments from nominal 110-240 V 50/60 Hz mains supplies.
To prevent loss of data should an external power supply be interrupted
for any reason during measurement, it is recommended that a usable set
of batteries be kept in the instrument.
In general, download all important data and remove the batteries
from the instruments when they are to be out of use for some time.
Note that when an instrument is returned to battery operation
after being powered from an external supply, either: switch the
instrument OFF then ON again, or: disconnect ALL devices from the DC
input socket, in order to avoid additional discharging of the internal
batteries.
The instrument contains a built in lithium battery to maintain
stored data and setups for periods while the instrument is switched OFF.
Introduction
Page 16 - CEL-450/490 Operators Handbook