LabJack U3 User Manual

Max V Min V
Single-Ended 2.44 0.0
Differential 2.44 -2.44
Special 0-3.6 3.6 0.0
Table 2-6. Nominal Analog Input Voltage Ranges (DAC1 Disabled)
differential input voltage of -2.44 volts means that the positive channel
much as 2.44 volts less than the negative channel, not that a channel can measure
ompared to ground, must be
the range -0.3 to +3.6 volts.
ve 12-bit resolution, they are returned justified as 16-bit values,
(Single-Ended)
m the table above. The
in t table ould be used if the actual
ll use the actual
n.
ious calibration values are stored in the Mem area. Generally
tion
nalog
es this automatically.
Note that the minimum
can be as
2.44 volts less than ground. The voltage of any analog input pin, c
in
The “Special 0-3.6” range is obtained by doing a differential measurement where the negative
channel is set to the internal Vref (2.44 volts).
lthough the binary readings ha
A
so the approximate nominal conversion from binary to voltage is:
olts(uncalibrated) = (Bits/65536)*Span
V
Volts(uncalibrated) = (Bits/65536)*Span – Span/2 (Differential)
Where span is the maximum voltage minus the minimum voltage fro
ctual nominal conversions are provided he s below, and sh
a
calibration constants are not read for some reason. Most applications wi
alibrations constants (Slope and Offset) stored in the internal flash.
c
Volts = (Slope * Bits) + Offset
Since the U3 uses multiplexed channels connected to a single analog-to-digital converter
ADC), all channels have the same calibration for a given configuratio
(
able 2-4 shows where the var
T
when communication is initiated with the U3, three calls will be made to the ReadMem func
to retrieve the first 3 blocks of memory. This information can then be used to convert all a
put readings to voltages. The high level Windows DLL (LabJackUD) do
in
Starting
Block #
Byte Nominal Value
0 0 AIN SE Slope 3.7231E-05 volts/bit
0 8 AIN SE Offset 0.0000E+00 volts
0 16 AIN Diff Slope 7.4463E-05 volts/bit
0 24 AIN Diff Offset -2.4400E+00 volts
1 0 DAC0 Slope 5.1717E+01 bits/volt
1 8 DAC0 Offset 0.0000E+00 bits
1 16 DAC1 Slope 5.1717E+01 bits/volt
1 24 DAC1 Offset 0.0000E+00 bits
2 0 Temp Slope 1.3021E-02 degK/bit
2 8 Vref @Cal 2.4400E+00 volts
2 16 Vref*1.5 @Cal 3.6600E+00 volts
2 24 Vreg @Cal 3.3000E+00 volts
Table 2-7. Calibration Constant Memory Locations
16

LabJack U3 Specifications

General

Analog Outputs	2
Analog Output Resolution	10 bits
Digital I/O	20
Counter/Timers	2
Interface	USB
Operating Voltage	5 V
Manufacturer	LabJack Corporation
Analog Inputs	16
Analog Input Resolution	12-bit
Max Sample Rate	50 kHz