Onset U12-008 Operating Manual

HOBO® U12 4-External Channel
Outdoor/Industrial Data Logger
(Part # U12-008)

Inside this package:

• HOBO U12 4-External Channel Outdoor/Industrial Data

Logger

• Desiccant pack

• Mounting/spare parts kit: two socket head screws, dome

plug and O-ring, O-ring lubricant, four mounting screws,
four flat washers, Allen wrench, and four tie wraps.

Thank you for purchasing a HOBO data logger. With proper
care, it will give you years of accurate and reliable
measurements.

The HOBO U12 4-External Channel Outdoor/Industrial data
logger has a 12-bit resolution and can record up to 43,000
measurements or events. The four external channels accept a
wide range of Onset and third-party sensors/transducers with
a 0-2.5 VDC output, including external temperature, AC
current, pressure, air velocity, and kW sensors. Specifications
for Onset sensors can be found at www.onsetcomp.com or by
contacting your Onset Authorized Dealer. For 0-5 VDC, 0-10
VDC, or 4-20mA output, use optional Onset Part No.
CABLE-ADAP5, CABLE-ADAP10, or CABLE-4-20mA
respectively.

The logger uses a direct USB interface for launching and data
readout by a computer.

Onset software is required for logger

operation. Visit www.onsetcomp.com for details.

Specifications

Measurement
range

Accuracy
(logger only)

Resolution 0.6mV
Time accuracy ± 1 minute per month at 25°C (77°F), see Plot A.
Operating range -20 to 70°C (-4° to 158°F)

Operating
temperature

Battery life 1 year typical use (see The Battery on page 4 for details)
Memory 64K bytes (43,000 12-bit measurements)
Weight 200 g (7 oz)
Dimensions 140 x 137 x 32 mm (5.5 x 5.38 x 1.25 inches)

External input channels (see sensor manual): 0 to 2.5 VDC
(with CABLE-ADAP5) and 0 to 10 VDC (with
CABLE-ADAP10)

± 2 mV ± 2.5% of absolute reading
± 2 mV ± 1% of reading for logger-powered sensors

Weatherproof case tested to NEMA 6 standard
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

Accessories

• Replacement Parts Kit (Part # H8X4-BK)

• Replacement Desiccant (Part # DESIC­PACK)

• U-Bolt (Part # U-BOLT-KIT)

© 2011 Onset Computer Corporation. Onset and HOBO are registered trademarks of Onset Computer Corporation. Other products and brand names
may be trademarks or registered trademarks of their respective owners.

Part #: MAN-U12008, Doc #: 13132-D

HOBO® U12 4-External Channel Outdoor/Industrial Data Logger

4-20mA Input Cable

This cable (part number CABLE-4-20mA) measures current
from 0 to 20.1 mA. Do not expose to current above 20 mA or to
negative current. Do not cut off the end of the gray cable where
it connects to the blue and yellow wires, as it contains the
precision resistor required for current measurement.

If you are using this cable outdoors, you will need to ensure that
the connection to your sensor or device is also weatherproof.
The connection between the gray cable and yellow and blue
wires is splash-proof, but not weatherproof.

Voltage Input Cable

The logger’s external inputs can accept the voltage input cable
(Onset part number CABLE-2.5-STEREO), which allows a
voltage to be recorded. The input line must not be exposed to
signals below 0 V or above 2.5 V.

If you are using this cable outdoors, you will need to ensure that
the connection to your sensor or device is also weatherproof.

Voltage Input Cable Connections

Wire Connection

Red Switched 2.5 V output
White Voltage input
Black Ground

Other External Sensors

Onset has a range of external temperature sensors, AC current
sensors, and cables for incorporating other sensors that are
compatible with the U12 4-External Channel Data Logger.
Measurement specifications for using Onset temperature and AC
current sensors with this logger are provided in the sensor
manuals. Visit www.onsetcomp.com for details on compatible
sensors.

computer. Special precautions may be necessary if any of your
voltage or current source common lines are not tied to earth
ground. Input isolators may be needed in industrial environments
to prevent errors caused by ground loops.

CAUTION: Analog channel input cannot exceed 2.5

VDC. For sensor outputs up to 10 VDC, use appropriate
voltage adapter cable.

Attaching the Sensors

1. Remove the socket head screws in the corners of the cover

and lift the cover from the device. Save the screws to
reattach the cover later.

2. Using a 15 mm wrench, remove the dome nut for the

channel you wish to connect to.

3. Pull the exposed end of the black rubber plug to remove it

from the fitting. Do not throw these plugs away! These
plugs are needed to maintain a weatherproof seal for
channels that are not connected to sensors or input cables.

4. Slide the dome nut over the plug end of the cable. The dome

nut’s threads should face towards the case.

5. Feed the plug end of the cable from the outside of the case

through the dome fitting of the channel you want to use
(refer to label on the logger’s cover) and plug it into the
corresponding port as shown in the diagram. The sensor

cable must be inserted through the fitting to ensure
proper logger operation. If you have difficulty inserting

the plug through the fitting, a small amount of dishwashing
liquid can be used as a lubricant on the plug. (Do not use O­ring lubricant.)

Switched 2.5 V Output

The external input channels have a switched 2.5 V output. This
signal can be used to power a sensor directly, or it can 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 1 ms before the
external channels are measured
and stays powered for 21 ms
after the external channels are
measured, as shown in the
diagram. The grey area shows
the 16 ms period during which
the logger samples the input
signals.

When using multiple voltage and/or current inputs, the (-) from
your current source(s) and the 0 V 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

6. Thread the dome nut back onto fitting and hand-tighten it.

Tighten an additional half-turn with a 15 mm wrench.

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