HP HP-18C - Calculator Maintenance; Clock Accuracy; Environmental Limits

Calculator Maintenance
To clean the display, use a cloth slightly moistened with water. Avoid
getting the calculator wet.
Do not lubricate the hinge.
Clock Accuracy
The system clock is regulated by a quartz crystal accurate to within
three minutes per month for normal operating temperatures. The ac-
curacy
of the clock crystal is affected by temperature, physical shock,
humidity,
and aging. Optimum accuracy is maintained at 25°C (77°F).
Environmental Limits
In order to maintain product reliability, you should observe the fol-
lowing temperature and humidity limits of the HP-18C:
• Operating temperature: 0° to 45°C (32° to 113°F).
• Storage temperature:
-20° to 65°C (-40° to 149°F).
•
Operating and storage humidity: 90% relative humidity at 40°C
(104°F) maximum .
C: Caring for and Using Your Calculator 191