HOBO U14 Data Logger User Manual
2
Plot
A:
Internal
Temperature
Sensor
Accuracy
and
Resolution
Specifications
LCD
Size
33
x
50.8
mm
(1.3
x
2
inches)
Elements
Temperature
and
relative
humidity
simultaneously
°C
or
°F
(selectable
within
host
software)
Memory
remaining
and
battery
level
Flashing
ALERT
for
out
‐
of
‐
limits
conditions
(selectable
within
host
software),
which
stops
flashing
on
offload
or
return
to
normal
range
Alarms
Set
points
High
and
low
set
points
for
both
temperature
and
relative
humidity
with
selectable
delays
Reset
options
Alert
conditions
reset
on
offload
or
return
to
normal
range
Selectable
Contact
Relay
Normally
Closed
or
Normally
Open
Contact
rating
48VDC,
1A
max
Contact
resistance
Less
than
1
Ohm
Range
0%
Low
Battery
Range
Communications
Method
Offloads
data
to
PC
or
U
‐
Shuttle
via
USB
cable
Speed
Readout
full
logger
(64K)
in
less
than
30
seconds
Time
accuracy
±1
minute
per
month
at
+20°C
(+68°F)
Power
3
AAA
Alkaline
batteries,
user
‐
replaceable
Dimensions
125
x
92
x
31
mm
(4.9
x
3.6
x
1.2
in)
Weight
170
g
(6.0
oz)
with
batteries
Internal
12
‐
Bit
Temperature
Sensor
Measurement
range
‐
20°C
to
+50°C
(
‐
4°F
to
+122°F)
Accuracy
±0.21°C
from
0°
to
50°C
(±0.38°F
from
32°
to
122°F);
±0.13°C
(0.24°F)
typical
(see
Plot
A)
Resolution
0.02°C
@
25°C
(0.04°F
@
77°F)
(see
Plot
A)
Response
time
15
minutes
(to
90%
in
airflow
of
1
m/sec)
Temperature
Accuracy
Drift
Negligible
Internal
12
‐
Bit
Relative
Humidity
Sensor
(User
replaceable)
Measurement
range
0
‐
100%
RH,
‐
20
to
50°C
(
‐
4
to
122°F)
Accuracy
+/
‐
2.5%
from
10%
to
90%
RH
(typical),
to
a
maximum
of
+/
‐
3.5%
including
hysteresis
(see
Plot
B)
Resolution
0.03%
RH
@
25°C
(77°F)
Response
time
2
minutes
(to
90%
in
airflow
of
1
m/sec)
Accuracy
Drift
<2%
over
5
years
typical
Hysteresis
1%
Typical
External
Sensors
For
External
Sensor
Specifications,
see
the
sensor’s
user
manual
Battery
Life
The
batteries
will
last
one
year
in
typical
conditions
(logging
intervals
of
≥
1
minute
with
weekly
offloads
and
average
temperatures
greater
than
10°C
or
+50°F).
Frequent
offloads
and/or
extreme
temperatures
will
reduce
battery
life.
At
temperatures
below
freezing
(0°C
or
+32°F),
batteries
will
typically
require
replacement
every
six
months.
In
these
conditions
the
battery
level
bar
graph
should
be
checked
regularly.
See
Battery
Level
Indicators
on
page
8.
The
CE
Marking
identifies
this
product
as
complying
with
all
relevant
directives
in
the
European
Union
(EU).
Temperature
Accuracy
and
Resolution
The
maximum
reading
error
for
the
internal
temperature
sensors
is
shown
at
right.
This
is
a
worst
case
error.
In
a
typical
logger,
temperature
errors
will
be
substantially
lower.
NIST
certification
of
temperature
accuracy
for
some
sensors
is
available
from
Onset.
The
temperature
resolution
for
internal
sensors
is
also
shown
at
right.
Resolution
is
the
smallest
difference
between
adjacent
temperature
steps
that
the
logger
can
report.
The
logger
will
typically
experience
little
or
no
accuracy
drift
unless
the
electronic
components
or
temperature
sensor
are
damaged
mechanically
or
by
exposure
to
environmental
factors
beyond
the
specifications,
such
as
high
heat
and
humidity.