The LabJack U12 has 8 screw terminals for analogue input signals (AI0-AI7). These can be configured individually as 8 single-ended channels, 4 differential channels, or combinations in between. Each input has a ±10 volt input range with 12-bit resolution. Differential channels can make use of the low noise precision PGA to provide gains up to 20, giving an effective resolution greater than 16-bits.
The LabJack U12 is capable of both software and hardware timed acquisition. When using software timed acquisition, the PC sends a command to the LabJack, and it responds with data. This mode can acquire 4 channels at up to 50 samples/second per channel. When using hardware timed acquisition, the PC sends a command to the LabJack telling it to start a burst or stream mode acquisition. In burst mode, up to 4,096 samples will be aquired from 1-4 channels at up to 8,192 samples/second and stored in the buffer. After the acquisition is complete, the data is transferred to the PC. A hardware trigger can be configured for burst mode that starts the acquisition when a digital input changes state. In stream mode, data is aquired from 1-4 channels at up to 1,200 samples/second and stored in the LabJack buffer. Simultaneously, the data is transferred from the LabJack buffer to the PC buffer, allowing the data to be streamed to disk continuously.
The LabJack U12 has 2 screw terminals for analogue output signals (AO0 & AO1). Each analogue output can be set to a voltage between 0 and the supply voltage (+5 volts nominal) with 10-bits of resolution. The analogue outputs are controlled in command/response mode at up to 50 Hz per channel.
The LabJack U12 has 20 digital I/O channels which can be individually configured as input or output.
Connections to 4 of the digital I/O are made with the built-in screw terminals (IO0-IO3). These 4 channels have built-in overvoltage/short-circuit protection. As inputs or outputs, they are controlled/read in command/response mode at up to 50 Hz per bit. As inputs only, they can be read with the high-speed burst and stream modes.
The remaining 16 digital I/O are accessed through the DB-25 connector and controlled/read in command/response mode at up to 50 Hz per bit. These channels can sink or source up to 25 mA each (total sink or source current of 200 mA max for all 16), allowing direct interface to many relays, such as the RO-16 board.
Counter and Watchdog
There is one 32-bit counter available on the LabJack U12 (screw terminal CNT), capable of counting frequencies up to 1 MHz. The counter is read in command/response mode at up to 50 Hz The LabJack U12 also has a watchdog timer function available which can change the states of digital I/O if the LabJack does not successfully communicate with the PC within a specified timeout period. This function could be used to reboot the PC allowing for reliable unattended operation.
The LabJack U12 free example applications:
- LJconfig: Lists all LabJacks connected to the USB and allows the local ID to be set on each.
- LJcounter: Reads the LabJack counter and provides the current frequency or count.
- LJfg (Function Generator): Outputs basic waveforms on AO0 (analog output zero).
- LJlogger: Saves data to disk, writes data to an HTML page on the Internet, and performs various actions (including email) on trigger events.
- LJscope: Simulates an oscilloscope by reading data from 2 AI channels in burst mode.
- LJstream: Uses stream mode to read, graph, and write to file, 4 AI channels.
- LJtest: Runs a sequence of tests on the LabJack itself.
- LJSHT: Retrieves and records data from 1 or 2 EI-1050 digital temperature/humidity probes.
- LJSHTmulti: Displays data from up to 20 EI-1050 digital temperature/humidity probes.
The LabVIEW source code for most of these applications is installed in the examples directory.
The free Express version of DAQFactory works with the U12. DAQFactory allows non-programmers to make custom applications. It is easy to collect input data, convert to engineering units, display it, and log it to file, without any programming. Scripting is also supported so you can do advanced applications with control and automatic setting of outputs.