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HOBO® U12 Temp/RH/
2 External Data Logger
(Part # U12-013)
Inside this package:
• HOBO U12 Temp/RH/
2 External Data Logger
• Mounting kit with magnet, hook
and loop tape, tie-wrap mount,
tie wrap, and two screws.
Doc # 7662-C, MAN-U12-013
Onset Computer Corporation
Thank you for purchasing a HOBO data logger. With proper care,
it will give you years of accurate and reliable measurements.
The HOBO U12 Temperature/Relative Humidity/2 External Data
Logger is a four-channel logger with 12-bit resolution and can
record up to 43,000 measurements or events. The two external
channels accept a variety of sensors, including temperature and
split-core AC current sensors as well as 4-20 mA and voltage
input cables (sold separately). The logger uses a direct USB
interface for launching and data readout by a computer.
An Onset software starter kit is required for logger operation.
Visit www.onsetcomp.com for compatible software.
Specifications
Temperature: -20° to 70°C (-4° to 158°F)
Measurement range
Accuracy
Resolution
Drift
Time accuracy ± 1 minute per month at 25°C (77°F), see Plot C
Response time in
airflow of 1 m/s
(2.2 mph)
Operating
temperature
Battery life 1 year typical use
Memory 64K bytes (43,000 12-bit measurements)
Weight 46 g (1.6 oz)
Dimensions 58 x 74 x 22 mm (2.3 x 2.9 x 0.9 inches)
RH: 5% to 95% RH
External input channels (see sensor manual): 0 to 2.5 DC
Volts
Temperature: ± 0.35°C from 0° to 50°C (± 0.63°F from
32° to 122°F), see Plot A
RH: +/- 2.5% from 10% to 90% RH (typical), to a
maximum of +/- 3.5%. See Plot B.
External input channels (see sensor manual): ± 2 mV ±
2.5% of absolute reading
Temperature: 0.03°C at 25°C (0.05°F at 77°F), see Plot A
RH: 0.03% RH
Temperature: 0.1°C/year (0.2°F/year)
RH: <1% per year typical; RH hysteresis 1%
Temperature: 6 minutes, typical to 90%
RH: 1 minute, typical to 90%
Logging: -20° to 70°C (-4° to 158°F)
Launch/readout: 0° to 50°C (32° to 122°F), per USB
specification
The CE Marking identifies this product as complying with
all relevant directives in the European Union (EU).
Plot A Plot B
Plot C
Important: Press this
button for 3 seconds
when logger is
launched with Button
Start or press for 1
second to record an
event while logging
USB interface
cable plugged
into logger
If the logger has never been connected to the computer before, it may take
a few seconds for the new hardware to be detected. Use the logger
software to launch and read out the logger.
Important: If you configure the logger to start with a button start, be
sure to press and hold down the button on the front of the logger for
at least three seconds when you want to begin logging data.
Be sure to plug any external sensors (if applicable) into the side of the
logger before logging begins. Also select the correct sensors and activate
the external channels in the logger software when configuring the launch.
Important: If you select an external channel, but do not plug the
probe in, false data will be recorded for that channel.
You can read out the logger while it continues to log, stop it manually
with the software, or let it record data until the memory is full.
Refer to the software user’s guide for complete details on launching,
reading out, and viewing data from the logger.
Sample and event logging
The logger can record two types of data: samples and events. Samples are
the sensor measurements recorded at each logging interval (for example,
the temperature every minute). Events are independent occurrences
triggered by a logger activity. Examples of events recorded
asynchronously during deployment include when the logger is connected
to the host, when the battery is low, the end of a data file once the logger
is stopped, and button pushes.
Press the button on the front of the logger for one second to record an
event. Both a button up and down event will be recorded. This is useful if
you want to mark the datafile at a particular point. For example, if the
logger is located in an incubator, you might press the button each time the
door is opened.
The logger stores 64K of data, and can
record up to 43,000 samples and events
combined.
Operation
A light (LED) on the side of the logger
confirms logger operation.
The following table explains when the
logger blinks during logger operation:
Channel 3
external input
Channel 4
external input
Light
Connecting the logger
The U-Family logger requires an Onset-supplied USB interface cable to
connect to the computer. If possible, avoid connecting at temperatures
below 0°C (32°F) or above 50°C (122°F).
1. Plug the large end of the USB interface cable into a USB port on the
computer.
2. Plug the small end of the USB interface cable into the bottom of the
logger as shown in the following diagram.
© 2008 Onset Computer Corporation
Part #: MAN-U12-013, Doc #: 7662-C
When: The light:
The logger is logging Blinks once every one to four seconds (the
The logger is awaiting a start
because it was launched in Start
At Interval, Delayed Start, or
Button Start mode
The button on the logger is
being pushed for a Button Start
launch
shorter the logging interval, the faster the
light blinks); blinks when logging a sample
Blinks once every eight seconds until launch
begins
Blinks once every second while pressing the
button and then flashes rapidly once you
release the button. The light then reverts to a
blinking pattern based on the logging interval
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HOBO U12 Temp/RH/2 External Data Logger
Protecting the logger
The logger can be permanently damaged by corrosion if it gets wet.
Protect it from condensation. If it gets wet, remove the battery
immediately and dry the circuit board with a hair dryer before reinstalling
the battery. Do not let the board get too hot. You should be able to
comfortably hold the board in your hand while drying.
Note! Static electricity may cause the logger to stop logging. To avoid
electrostatic discharge, transport the logger in an anti-static bag, and
ground yourself by touching an unpainted metal surface before handling
the logger. For more information about electrostatic discharge, visit our
website at http://www.onsetcomp.com/Support/support.html.
Using external sensors
The external input channels have a switched 2.5 V output. This signal can
be used to power a sensor directly or it can also be used to trigger an
external circuit. External sensors should draw no more than 4 mA total
when powered. The switched 2.5 V output turns on about 15 ms before the
external channels are measured and stays powered for 48 ms after the
external channels are measured, as shown in the following diagram. The
striped bar shows the 16 ms period during which the logger samples the
input signals.
16 ms
15 ms
48 ms
When using multiple voltage and/or current inputs, the (-) from your
current source(s) and the 0 Volt line of your voltage source(s) are tied
together at the logger. If these lines are at different voltage potentials, this
may cause inaccurate readings or even damage your logger. Keep in mind
that these lines may also be tied to earth ground through your PC interface
cable when connected to your computer. Special precautions may be
necessary if any of your voltage or current source common lines are not
tied to earth ground.
Using the RH sensor
In order to take humidity measurements, the temperature sensor must be
used in conjunction with the RH sensor.
Conditions outside the recommended range may offset the RH signal.
Vapors may also affect the RH sensor. The diffusion of chemicals into the
sensor may cause a shift in both offset and sensitivity. High levels of
pollutants may cause permanent damage to the sensor.
Upon returning to normal conditions, the RH sensor will slowly return
towards calibration state by itself. However, prolonged exposure to
© 2008 Onset Computer Corporation. All rights reserved.
Part #: MAN-U12-013, Doc #: 7662-C
Onset and HOBO are registered tr ademarks of Onset Computer Corporation. Other products
and brand names may be trademarks or registered trademarks of their respective owners.
extreme conditions may accelerate aging and eventually lead to a
permanent shift. To recondition the sensor, do the following:
1. Remove the battery
2. Warm 24 hours 80–90°C (176–194°F) at < 5% RH
3. Re-hydrate 48 hours 20–30°C (70–90°F) at 75–95% RH
Mounting
There are four ways to mount the logger using the materials in the
mounting kit included with the logger:
• Use the hook and loop tape to affix the logger to a surface.
• Attach the magnet, then place the logger
on a magnetic surface.
• Use the tie wrap and tie wrap mount to
tie the logger to an object.
• Fasten the logger to a surface with the
32 mm
(1¼ inch)
two Phillips-head screws. The back of
the logger has two inserts for the screws,
32 mm (1¼ inches) apart.
Battery
The logger requires one 3-Volt CR-2032 lithium battery. Expected battery
life varies based on the temperature and the frequency at which the logger
is recording data (the logging interval). A new battery will typically last
one year with logging intervals greater than one minute. Deployments in
extremely cold or hot temperatures or logging intervals faster than one
minute may significantly reduce battery life.
To replace the battery:
1. Disconnect the logger from the computer.
2. Unscrew the logger case.
3. Lift the circuit board and carefully push the battery out with a small
blunt instrument, or pull it out with your fingernail.
4. Insert a new battery, positive side facing up.
5. Carefully realign the logger case and re-fasten the screws.
WARNING: Do not cut open, incinerate, heat above 85°C
(185°F), or recharge the lithium battery. The battery may explode if the
logger is exposed to extreme heat or conditions that could damage or
destroy the battery case. Do not dispose of the logger or battery in fire.
Do not expose the contents of the battery to water. Dispose of the
battery according to local regulations for lithium batteries.
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