User Manual - Comet System, s.r.o.
Temperature and relative humidity logger
Instruction Manual
Instruction manual for use of temperature and RH logger R3120
Logger is designed for measurement and record of ambient temperature and relative humidity.
Measuring sensors of temperature and humidity are attached to logger. Measured values including
calculated dew point temperature are stored in selectable time interval to internal nonvolatile
memory. All logger control and setting are performed from the PC and password is applicable. It is
enabled to switch ON and OFF the logger by delivered magnet (this possibility can be in
configuration disabled). It is also enabled to program automatic start in certain day and time (for one
month forward).
Switched ON logger every 10 seconds (independently on logging interval) updates MIN/MAX
memory, compares measured values of each quantity with two adjustable limits for each quantity
and exceeding of limits is indicated by LED diode (alarm function). Also memory alarm mode is
selectable, when alarm is indicated permanently till alarm memory reset. Alarm function is enabled
or disabled for each quantity individually.
Logging mode can be adjusted as non-cyclic, when logging stops after filling the memory. In
cyclic mode oldest stored values are overwritten by new. In addition logging mode can be selected
when logging is active only if measured value is out of adjusted alarm limits.
Stored values can be transferred from logger memory to the PC by means of communication
adapter. Communication adapter can be connected to the logger permanently – data logging is not
interrupted even if data download appears.
Logger evaluates minimum battery voltage and its drop below allowed limit is indicated by red
LED. At the same time remaining battery capacity is available in % by means of the PC program. It
is valid if logger is operated at temperature from -5 to +35°C. If logger is operated often outside of
the above temperature range battery life can be reduced to 75%, i.e. if displayed remaining battery
capacity drops below 25%, it is recommended to replace the battery.
Technical parameters:
Measuring parameters:
Ambient temperature (RTD sensor Pt1000/3850ppm):
Measuring range: -30 to +80 °C
Resolution: 0.1 °C
Accuracy: ± 0.4 °C
Relative humidity (reading is temperature compensated at entire temperature range):
Measuring range: 0 to 100 %RH
Resolution: 0.1 %RH
Accuracy: ± 2.5 %RH from 5 to 95 %RH at 23 °C
Dew point (value calculated from temperature and humidity):
Range: -60 to +80 °C
Resolution: 0.1 °C
Accuracy: ± 1.5 °C at ambient temperature T < 25°C and RV > 30 %, for
more details see Appendix A
Response time with plastic sensor cover (air flow approximately 1 m/s):
temperature: t63 < 2 min, t90 < 8 min (temperature step 20 °C)
relative humidity: t63 < 15 s, t90 < 50 s (humidity step 30 %RH, constant temperature)
Measuring interval, alarm evaluation and MIN/MAX memory update:
standard mode (no low-power mode): every 10 s
low-power mode: every 1 minute
Logging interval to memory:
standard mode: 10 s to 24 h (20 steps)
low-power mode: 1 minute to 24 h (17 steps)
Memory capacity:
for non cyclic mode
16 252 T+RH values
for cyclic mode
15 296 T+RH values
Specified values are maximum possible and can be reached only if record is not interrupted
(since last memory erasing)
Communication with computer: via RS232 (serial port) by means of COM adapter or USB
port by means of USB adapter; data transfer from logger via communication adapter is
Real time clock: adjustable from computer, integrated calendar including leap years
Error of internal RTC: < 200 ppm (i.e. 0.02 %, 17.28 s in 24 h)
Power: Lithium battery 3.6 V size AA
Typical battery life:
standard mode (data download to the PC approximately once a week): 3 years
low-power mode (data download to the PC approximately once a week): 7 years
on-line mode with interval 1 minute: min. 2 years
on-line mode with interval 10 seconds: min. 1 year
Notice: the above lives are valid if logger is operated at temperature from -5 to +35°C. If
logger is operated often outside of the above temperature range life can be reduced to 75%
Protection: electronics IP67, sensors are protected by a cover with IP30 protection
Operational conditions:
Operational temperature range: -30 to +80 °C
Operational humidity range: 0 to 100 %RH
Specification of outer characteristics accordingly to Czech National Standard 33-2000-3:
normal environment accordingly to appendix NM: AE1, AN1, AR1, BE1
Operational position: negligible
Logger installation: by self adhesive Dual Lock, applied to clean, flat surface
Not allowed manipulation: it is not allowed to remove sensor cover and mechanically
damage sensor under cover. Sensors of temperature and humidity should not get to
direct contact with water or other fluids.
Limit condition: temperature -40 to +80 °C, humidity 0 to 100 %RH
Storing condition: temperature -40 to +85 °C, humidity 0 to 100 %RH
Dimensions: 93 x 64 x 27 mm
Weight including battery: approximately 105 g
Material of the case: ABS
Logger operation
Logger comes complete with installed battery and switched OFF. Before operation it is
necessary by means of installed user PC software to set logging parameters and other features. Free
user program is available to download at . For communication with the PC a
communication adapter is necessary (not included in delivery). For connection via RS232 serial port
it is necessary to use COM ADAPTER, for connection via USB port it is necessary to use USB
ADAPTER. Connect adapter connector to proper computer port and plug the adapter to the guide
slots on the side of logger.
Connecting logger to the computer by means of communication adapter
Notice: USB connector can be located also from the computer front side
After connecting the logger to the computer reading of logger info is enabled by means of the
PC software and also setting of the instrument accordingly to the user needs (menu Configuration /
Setting of instrument parameters). Before logging start it is necessary:
check or optionally set the logger real time clock
select suitable logging interval
select logging mode (cyclic or non cyclic)
switch ON the logger (or switch OFF, if it is about to be switched ON by magnet or
automatically with delayed start)
enable or disable the option to switch ON the logger by magnet
enable or disable the option to switch OFF the logger by magnet
set date and time of logger automatic switching ON logger or disable this option
select if record runs permanently or only if alarm is active
If alarms are about to be applied, set both limits and enable alarm
optionally enable permanent alarm (alarm with memory)
reset memory of MIN/MAX values (if needed)
check free space in data memory, optionally erase data memory of the logger
enter password if protection against unauthorized manipulation with the logger is necessary
Logging interval between to subsequent measurements is specified by the user. Memorizing of the
first value is synchronized with the internal real time clock, so the logging is performed at sharp
multiples of minutes, hours and days. E.g. after starting the logging with the 15 minute interval the
first value is not stored immediately, but after the internal clock gets the status of a quarter, a half or
a whole hour. After starting the logging with the 6 hour interval the first value is stored at that
whole hour to perform the storing also at 00.00, i.e. at the beginning of the day. First storing is
performed at 6.00,12.00, 18.00 or 00.00hour - at the hour from the above nearest to the logging
start. After communication with computer or after start by magnet logger automatically waits for the
nearest whole multiple of time and then first measurement is performed. This is also necessary to
take into account when setting time of automatic logger switch ON.
Notice: If logger operates as permanently connected to the computer, using of magnet start/stop
is disabled.
To enable the logger control by magnet is suitable only in cases, when possibility of
unauthorized manipulation to the logger operation is eliminated.
Indication of logger state in usual operation
Switched OFF logger has both indication LEDs permanently OFF. It does not do any function
except eventual communication with the PC and the consumption from battery is negligible. If any
modification of configuration of switched OFF logger is done from the PC, yellow LED blinks
shortly at the moment of sending data to logger and then immediately red LED to indicate, logger is
still switched OFF.
After switching ON the logger yellow LED lights up for 2s and switched ON logger is indicated
by repeated short blink of yellow LED marked LOG with 10s interval. If alarm is active, yellow and
red LEDs blink simultaneously. To apply the alarm function, it is necessary to enable from the PC
alarm evaluation and at the same time set its lower and upper limits. If measured temperature is
inside of the limit range, alarm is not active. If measured value exceeds any of set limits, alarm is
indicated. "Memory" alarm mode is selectable, when once indicated alarm is indicated permanently
till it is reset from the PC. Alarm indication is also automatically reset with every new logger start.
If memory is filled in non-cyclic logging mode, record stops and logger switches OFF. This
state is indicated by accelerated blinking of red LED with 3s interval.
10 s
switched ON
yellow 
active alarm
yellow 
red 
full memory
yellow 
red 
Indication of the logger state beyond normal operation
If yellow LED lights up after start extra long (depending to memory occupation up to 12s),
initialization of the logger proceeds. This can occur e.g. after totally discharged battery replacement.
In that case correct time setting from the PC is necessary.
If red LED blinks immediately after yellow LED (do not mistake with active alarm indication!),
end of calculated battery life is indicated – logger is fully functional, early battery replacement is
If only red LED blinks 2x with 3s interval, battery voltage is low and logger is not enabled to
switch ON. If logger was originally switched ON, record is interrupted and logger is switched OFF.
Communication with computer can work for limited period of time. Replace the battery as soon as
end of
battery life
low battery
10 s
yellow 
red 
yellow 
red 
Procedure of switching ON / OFF the logger by magnet
Start / stop by magnet
The function must be enabled from the PC before. If only switching OFF by magnet is enabled,
it is of course necessary to switch ON the logger from the computer.
Switching the logger ON by magnet
Plug magnet to guide slots from logger front side and wait approximately 1 s for yellow LED to
light up. After lighting up it is necessary immediately (till it lights) to remove magnet from guide
slots and logger switches ON and yellow LED blinks every 10s. If magnet is applied for more than
3s yellow LED goes out and logger remains switched OFF.
Switching the logger OFF by magnet
The procedure is identical with the above procedure for switching ON. If indication yellow
LED does not light up to 1 second after plugging the magnet, it is necessary to unplug magnet and
repeat the procedure.
Battery replacement
Low battery is indicated by red LED, which blinks itself (without yellow LED – see tables
above). Replace the battery for new one. If logger is operated often in temperature below -5°C or
over +35°C and PC program indicates remaining battery capacity below 25% it is also
recommended to replace the battery. Applied is Lithium battery 3.6 V, size AA. Battery is located
under logger lid.
Warning: near battery fragile glass reed contact is located – be careful not to damage it. Be
careful in battery replacement!
Replacement procedure:
switch off the logger by the PC program or by magnet (if low battery allows)
unscrew four corner screws and remove the lid
remove old battery by pulling the glued tape
insert new battery respecting the correct polarity (see symbols + and – near battery holder). If
you connect new battery up to 30 s, all logger settings remain unchanged. In the opposite case
check by means of PC program all settings, especially the real time clock in logger. Attention,
inserted battery with incorrect polarity causes logger damage!
put the lid back again and screw four screws. Be careful to have the rubber sealing properly in the
slot and tighten the screws properly to ensure the water resistance of the instrument.
connect logger to the computer and write to it the information on battery replacement (menu
Configuration/Battery replacement). This step is necessary to evaluate properly the remaining
battery capacity.
Discharged battery or entire instrument after its life liquidate ecologically – in special
Instrument passed through tests of electromagnetic compatibility (EMC):
Device conforms in accordance with EN 61326-1 these norms:
EN 55011 Class B
EN 61000-4-2 (levels 4/8 kV, Class A)
EN 61000-4-3 (intensity of electric field 3 V/m, Class A)
EN 61000-4-4 (levels 1/0.5 kV, Class A)
EN 61000-4-6 (intensity of electric field 3 V/m, Class A)
Appendix A - Accuracy of dew point measurement
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