Figure 1. LabJack U12 top surface.
Figure 1 shows the top surface of the LabJack U12. Not shown are the USB and DB25
connectors, 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.
•
AI0 – AI7:
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
µ
A.
o
Single-Ended: The input range for a single ended measurement is ±10 volts.
o
Differential channels can make use of the PGA to provide gains up to 20, giving an
effective resolution greater than 16-bits. In differential mode, the voltage of each AI with
respect to ground must be between ±10 volts, but the range of voltage difference
between the 2 AI is a function of gain (G) as follows:
G=1
±20
volts
G=2
±10
volts
G=4
±5
volts
G=5
±4
volts
G=8
±2.5
volts
G=10
±2
volts
G=16
±1.25
volts
G=20
±1
volt
•
AO0 & AO1:
The LabJack U12 has 2 screw terminals for analog output voltages. Each analog
output can be set to a voltage between 0 and the supply voltage (+5 volts nominal) with 10-bits of
resolution.
•
IO0 – IO3:
Connections to 4 of the LabJack’s 20 digital I/O are made at the screw terminals, and
are referred to as IO0-IO3. These 4 channels include a 1.5 k
Ω
series resistor that provides
overvoltage/short-circuit protection.
•
D0 – D15:
Connections to 16 of the LabJack’s 20 digital I/O are made at the DB25 connector,
and are referred to as D0-D15. These 16 lines have no overvoltage/short-circuit protection, and
