ROTRONIC HygroLog HL20 - Manual (Page 5)

IN-E-HL20-V1_12
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
HygroLog HL20 and HL21 data logger:
User Guide Instruction Manual
Document Type
Page 5 of 17
Document title
© 2010-2011; Rotronic AG IN-E-HL20-V1_12
Battery lifetime in months
Models w/o LC display 20
Models with LC display, display sleep function set to 1 minute 13
Models with LC display, display sleep function disabled 5
2.4 Real time clock
After inserting a fresh set of batteries for the first time, the real time clock must be adjusted prior
to using the HL20 or HL21 (see
“Operation”). The real time clock is powered from a large
capacitor and can run for up to 4 hours without the batteries. Removing the battery for an
extended period of time will cause the logger to completely lose track of the date and time.
Because of the requirement to always keep track of the date and time, the HL20 and HL21 do not
have a power on/off switch.
2.5 Memory
All models use a non-volatile EEPROM internal memory to hold the measurement data. The
memory cannot be removed from the data logger.
Memory capacity is as follows:
HL20: 20,000 pairs of relative humidity and temperature values
HL21: 20,000 temperature values
2.6 Function key
The function key is used as follows:
Long key press: press the key for a few seconds to start or stop data logging.
Short key press: depending on the configuration settings of the display (display sleep
function) a short key press turns on and off the optional LC display.
For more details, see “Operation”
2.7 Status indicator (LED)
The status indicator consists of a green and red LED. The green side of the LED flashes every 5
seconds when logging is active. The red side of the LED flashes every 5 seconds when a
measured value is out of limits (see
“Configurable settings”) or when the logger requires attention
(low battery, memory full, major sensor failure – such as open or shorted sensor)