Hardware Description - LabJack U12 User Manual

Start => Programs => LabJack => LJtest.
Make sure "Test Fixture Installed" and "Continuous" are not selected, and press the "Run" button. LJtest will step through 8
separate tests and all should pass.

2 - Hardware Description

The external features of the LabJack U12 are:
USB connector,
DB25 digital I/O connector,
Status LED,
30 screw terminals.
The USB connection provides power and communication. No external power supply is needed. The +5 volt connections available
at various locations are outputs, do not connect a power supply.
Figure 2-1. LabJack U12 top surface.
Figure 2-1 shows the top surface of the LabJack U12. Not shown is the USB and DB25 connector, which are both on the top edge.
The DB25 connector provides connections for 16 digital I/O lines, called D0-D15. It also has connections for ground and +5 volts.
All connections besides D0-D15, are provided by the 30 screw terminals shown in Figure 1. Each individual screw terminal has a
label, AI0 through STB.
The status LED blinks 4 times at power-up, and then blinks once and stays on after enumeration (recognition of the LabJack U12
by the PC operating system). The LED also blinks during burst and stream operations, unless disabled. The LED can be
enabled/disabled through software using the functions AISample, AIBurst, or AIStreamStart. Since the LED uses 4-5 mA of
current, some users might wish to disable it for power-sensitive applications.
2.1 - AI0-AI7
Hardware
The LabJack U12 has 8 screw terminals for analog input signals. These can be configured individually and on-the-fly as 8 single-
ended channels, 4 differential channels, or combinations in between. Each input has a 12-bit resolution and an input bias current of
±90 µA.
Single-Ended: The input range for a single-ended measurement is ±10 volts.
Differential channels can make use of the low noise precision PGA to provide gains up to 20. In differential mode, the
voltage of each AI with respect to ground must be between +20 and -10 volts, but the range of voltage difference between the
2 AI is a function of gain (G) as follows:
G=1 ±20 volts
2