value and then jump to a higher value, recording that value for a while. The difference
between the steps is twice the quantization error since a perfectly calibrated logger will
never be more than half a step away from the actual value.
Differences between loggers
The calibration process adjusts the measured values of individual loggers with the same
temperature range. This means that two loggers will not necessarily have the same step
values, so that two loggers exposed to the same temperatures may report different values.
Each one will be correct within its accuracy.
The coffee mug logger test
The freezing point of water is 0°C (+32°F) with only a tiny dependence on pressure and
the salt levels found in normal tap water. You can use this information to test the
accuracy of your StowAway TidbiT logger. Put crushed ice and water in an insulated
container, and completely submerge the logger in the ice water. Place the container in a
refrigerator to minimize temperature gradients. Leave it in for fifteen minutes while
logging to be sure the TidbiT reaches equilibrium. Offload the data and blow up the end
of your plot to check the logger’s accuracy. The actual temperature will be above 0°C,
though less than 0.1°C if you do everything right.
Five minute response time in water
Plot D shows that the temperature reached
90% of the step change in about five
minutes. In air moving 1m/sec, response
time to reach 90% of the step change is
typically 20 minutes. The logger is so
small that you can fit a
dozen of them in a coffee
Plot D Response Time
StowAway® TidbiT® User’s Manual
Thank you for purchasing a StowAway TidbiT temperature
logger. The minimum optic logging system is comprised of
these components: the StowAway TidbiT temperature logger,
Optic Base Station, TidbiT Coupler, and logger software.
Launch and recovery
Launching your StowAway TidbiT
Connect the Optic Base Station to the host computer using the appropriate interface cable
(CABLE-PC-3.5 for a PC and CABLE-MAC-HOBO for a Macintosh). Place the
StowAway TidbiT onto the TidbiT Coupler attached to the Optic Base Station. Refer to
the Optic Base Station User’s Manual for proper alignment. Refer to the software user’s
manual for launching procedures. Recommended software: BoxCar® 3.6+ or any version
of BoxCar Pro.
Triggered launch and the StowAway TidbiT
The StowAway TidbiT has an optional triggered launch. Launch your logger choosing
the triggered launch option. The magnetically operated reed switch is activated when the
TidbiT Coupler is reconnected to the logger and then removed. The Optic Base Station
and TidbiT Coupler are not necessary to trigger the launch. Any strong magnet placed
near the face of the logger will trigger the launch. The StowAway Tidbit’s green LED
light will flash brightly four times to indicate successful triggered launch.
Seeing if the alarm has been tripped
The StowAway TidbiT has two LEDs. The green LED blinks during use if it has not seen
out-of-range conditions (see the software user’s manual for how to set the alarm). Note
that the alarm can be set up to +70°C on the -20°C to +50°C TidbiT, but we recommend
staying within the +50°C range of the logger. If it has recorded out-of-range conditions,
the red LED will blink. When the StowAway TidbiT is full, neither LED will blink.
The CE Marking identifies this product as complying with all relevant directives in the European
Union (EU).
© 1996–2011 Onset Computer Corporation. All rights reserved. Onset, HOBO, StowAway, TidbiT,
and BoxCar are trademarks of Onset Computer Corporation.
Onset Computer Corporation
470 MacArthur Blvd., Bourne MA 02532
Mailing: PO Box 3450 Pocasset MA 02559-3450
Telephone: 1-800-LOGGERS (564-4377) 508-759-9500
Fax: 508-759-9100
Data recovery
After the StowAway TidbiT has been launched, remove the logger from the TidbiT
Coupler and deploy the logger. At the end of the deployment, reconnect the logger to the
TidbiT Coupler attached to the Optic Base Station for readout. The StowAway TidbiT
communicates at 1200 baud. The cleverly optimized software reads out 8K of data in 1.5
minutes, and 32K in 6 minutes.
Sealed logger designed for field operation
The StowAway TidbiT uses optical communication because it is completely sealed. This
means that the logger can be used in wet or dirty locations or even completely
submerged. The logger can be launched and readout directly to a host computer using the
TidbiT Coupler, the Optic Base Station, and the appropriate interface cable. Data can also
be readout in the field with the Optic Shuttle, Onset’s unique field data transporter. For
data retrieval be sure to clean your logger of dirt and dust. To clean your TidbiT use only
a non-abrasive mild soap and warm water with a non-scratching sponge or cloth. Any
scratches or abrasions on the TidbiT's surface may impair communication. (For tougher
cleaning jobs use a plastic polish such as Novus® plastic polish.)
3050-J MAN-TBI32
Hardware details
Accuracy of two different temperature ranges
Time accuracy
At room temperature, the logger’s idea of time can vary from
the actual time by as much as one hour per year (100 ppm).
There is an additional temperature effect shown in Plot A.
Depth: rated to 1000 feet
Just for fun, we tested the StowAway TidbiT at really high
pressures. Although they worked at 5000 psi (10,000 ft water
depth equivalent) we are not prepared to test all of them to
this depth. We allowed a conservative factor of 10, rating
them to 1000 ft.
Graph 1093
Timebase dependence
Plot A
Temperature accuracy and resolution
The StowAway TidbiT logger’s accuracy and resolution
specifications are given in plot B and plot C. The logger’s
accuracy specification is its maximum measurement
error, including the effects of thermistor error and
quantization error. In most cases the logger’s actual
accuracy is better than the specified value. The logger’s
resolution is the difference between temperature steps.
Model TBI32-05+37: Range -4°C to 37°C (24°F to
99°F)*; Model TBI32-20+50: Range -20°C to50°C
(-40°F to 122°F)
Plot B: Graph 4029-B
Model TBI32 (-20°C to +50°C)
Operating temperature range -20°C to +50°C
The StowAway TidbiT will operate properly in the temperature range -20°C to +50°C. It
will record temperatures up to +70°C but exposure to temperatures above +50°C or
below -20°C will reduce the battery life. For temperatures above the highest value in its
range, it will read its highest value, and for temperatures below the lowest value in its
range, it will read its lowest value.
*Specified range is narrower than nominal range due to
precision calibration process.
Notice: To guarantee specified accuracy, the TidbiT and Optic StowAway units should
not be used in condensing environments and water temperatures higher than +30°C
(+86°F) for more than eight weeks cumulatively. Prolonged exposure will lead to
measurement drift and eventual failure. If your application temperatures and environment
are questionable based on the above statement, please contact Onset or your authorized
Onset dealer for more information.
Individual calibration
Factors that affect the StowAway TidbiT’s accuracy are
the thermistor error, component imperfections (resistor
variations and A-D nonlinearities), and quantization
error (difference between temperature steps). Most
StowAways use thermistors with a 0.2°C
interchangeability in the range 0°C to +75°C. The
StowAway TidbiT model TBI32 -05+37, uses a
thermistor that has 0.1°C interchange ability. Onset
Computer Corporation’s proprietary test procedures
effectively eliminate the resistor and A-D errors, leaving only the thermistor error,
quantization error, and a small residual calibration error.
Five year battery life
The StowAway Tidbit has a five-year battery life in typical use. This corresponds to 16
three-month deployments in water (+35°F to +80°F) with 4 minute or longer intervals, no
multiple sampling and one offload per deployment. Alternatively, if the logger is used
constantly in short duration applications, the battery life can be substantially reduced.
Examples of the battery life in short deployments are: 6,000 one-hour deployments with
no multiple sampling, 5,000 two-hour deployments with no multiple sampling, and 70
four-day deployments with multiple sampling. Sampling intervals shorter than 1 minute
and/or extended storage or deployment above +80°F will significantly reduce battery life.
The battery is not replaceable.
1.2 x 1.6 x 0.63 inches and 0.68 oz
The shape of the StowAway TidbiT was chosen to minimize the logger’s volume. The
thermistor has been placed on the PC board in the logger to provide enhanced protection
for the sensor and further improve the already high reliability of these loggers. The logger
weighs 0.68 oz. (19.5 g) and is negatively buoyant.
The TidbiT will measure temperature in the grey area, but
exposure to temperatures in this range will reduce the
TidbiT’s battery life.
The blinking LEDs
Waiting for trigger: Weak green blink every six seconds.
Waiting out delay: Weak green blink every four seconds.
Logging: Bright green blink every measurement, and weak every two seconds between
measurements. If the StowAway TidbiT is in multiple sampling mode, it will blink at
each measurement, not each time data is recorded.
Alarm: A logger is out-of-range if it has recorded a value that is above the high alarm
limit or below the low alarm limit. The red LED will blink during the duration of the
deployment instead of the green LED.
What is quantization error?
Ideally a logger would record a different temperature for
each temperature applied to it. The StowAway TidbiT
can store only 255 different temperature values in its
temperature range. If you exposed the logger to a slowly
rising temperature, the logger would record a constant
Plot C: Graph 4024
Model TBI (-5°C to +37°C)