Thank you for buying a HOBO data logger. With proper care it will give you years of accurate and
reliable measurements.
This manual covers the HOBO H8 4-Channel External data logger. This logger can store 32,520 time-
stamped measurements and is compatible with the HOBO Shuttle allowing for convenient retrieval of
field data.
Specifications
Operating range (logger): -4°F to +158°F (-20°C to +70°C),
0 - 95% RH non-condensing
Time accuracy: approx. ±1 minute per week (±100 ppm at +68°F or +20°C),
full dependance shown in Plot A
Measurement capacity: 32,520 measurements total, stored in
nonvolatile memory
Drop proof to 5'
Size: 2.4" H x 1.9" W x 0.8" D
Weight: approximately 1 oz.
Battery: CR-2032 (lithium), user-replaceable
Battery life (continuous use): 1 year
Storage temperature: -40°F to +167°F (-40°C to +75°C)
External Sensors - Onset has a range of external temperature and AC
current sensors that are compatible with the HOBO H8 4-Channel External
logger. Measurement specifications for using Onset temperature and AC
current sensors with this logger are provided
in the sensor manuals. For compatible sensors, see the HOBO
catalog, contact Onset Computer Corporation or contact an Onset Authorized
Dealer.
When using multiple voltage inputs, current inputs, or a combination of both
input types; keep in mind that the (-) from your current source(s) and the
(0V) line of your voltage source(s) will be tied together when installed on
the logger. The lines must be at the same voltage potential or inaccurate
readings or even damage to the logger may occur. You must also take into
account 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.
4-20 mA Input cable - This cable (part number CABLE-4-20mA)
measures currents from 0 to 20.1 mA. The accuracy is ±0.1 mA ±3% of
reading. The 4-20 mA cable must be connected such that the current flows
through, and with the proper polarity, as shown in Diagram A. Do not
expose to current above 20 mA or negative current. Do not cut off the end
of the gray cable where it connects to the blue and yellow wires as that
contains the precision resistor required for current measurement.
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. This input reads 0 to 2.5 DC volts, with a ±0.1 µA
maximum leakage between measurements and a ±0.4 µA leakage during sensor measurements (5.4 ms
each). The accuracy is ±10 mV ±3% of reading. Input impedance is 10k
Ω
. The input line should not be
exposed to signals below 0 volts or above 2.5 volts.
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 switches on about
4.5 ms before the first channel is measured and stays powered
for 11 ms after the last channel is measured, as shown in
Diagram B. The gray bars show the 2 ms periods during which
the HOBO samples the input signals. Diagram B shows the
envelope when all four channels are enabled. For each disabled channel, the envelope is 16.5 ms shorter.
Connecting the Communications Cable and Launching
A Starter Kit, which includes the appropriate PC interface cable and software, is required to
operate your logger. Connect the PC interface cable into the 3.5 mm
jack on the logger, as shown in Diagram C, and into a working
serial port of your computer. Install and start the logger's software.
Select Launch... under Logger on the menu bar and a launch
dialog box will be provided. For a complete explanation on
installing the software and launching your logger, please refer to
the logger software manual.
Continued on next page
Voltage Input Cable Connections
red wire
switched 2.5 V output
white wire
voltage input
black wire
Ground
Plot B
Temperature Accuracy
and Resolution TMC6-HA
(wide accuracy thermister cable)
Plot C
Temperature Accuracy
and Resolution TMC6-HB
(high accuracy thermister cable)
