Data Acquisition with DCS 2.0

by Christopher M. Borys, February 01, 2008

Presently, the I/O signal engine (IOMON 3.0) on Borynet Data Control Server (DCS 3.0) supports two different data acquisition devices: USB LJ-U12 and USB LJ-U3. Intended for rather small systems and cost effective solutions, the system is ideal for data acquisition ranging from 1 to 50 signals. In this guide, we will attempt to explore some of these possibilities.

Both devices, LJ-U3 and LJ-U12, manufactured by LabJack Corporation, are using USB 1.1/2.0 bus for data acquisition and 12-bit precision for analog input. The USB bus also provides necessary power the DAQ device. With a dedicated driver developed by Borynet, both devices are easily configurable and ready to use.

The LJ-U12 can handle up to 8 single-ended (or 4 differential analog input), 2 analog outputs and 4 digital I/O signals. The additional 16 digital I/O signals can be handled through extension board. A dedicated relay board is also available. The analog input range ±10 V combined with programmable gain amplifier PGA on a differential input allows for variety of input ranges: ±20V, ±10V, ±5V, ±4V, ±2.5V, ±2V, ±1.25V, and ±1V.

The LJ-U3 main board can handle up to 8 flexible I/O, 1* analog output, and 2 counters. The additional 8 flexible I/O can be configured using dedicated extension board. The flexible I/O can be configured as analog input, digital input, or digital output. The analog input can be single-ended or differential; however, one differential input counts for two physical connections. When single-ended (SE) input is used the voltage range can be 0-2.44V or 0-3.6V. For differential analog input the range is ±2.44V. The LJ-U3 has also built-in a temperature sensor.

(*) Note, that the second analog output is only available in certain configurations and we are not supporting it due to not stable conditions to provide quality analog input.

The main advantage of LJ-U12 is range of voltages than can handle with out any additional gear. The advantages of LJ-U3 lie in flexible configuration as well as in variety of dedicated extension modules. These modules are designed to fit right into terminals of LJ-U3 and provide additional functionality. For example, the are modules to handle 4-20 mA signals or voltages ranges ±10V.

LJ-U3 Configurations

[Device=1]
name=my-LJU3-01
type=LJ-U3

• Single-ended analog signal on FIO0. Input range 0 to 2.44V. Positive wire connected to FIO0 and negative to ground (GND).

  [Analog=x]
  Device=y
  Type=Input
  PosChannel=0
  

• Single-ended analog signal on FIO1. Input range 0 to 3.6V. Positive wire connected to FIO1 and negative to ground (GND). Specify Subtype=SEVref or NegChannel=30.

  [Analog=x]
  Device=y
  Type=Input
  SubType=SEVref
  Channel=1

• Differential analog input signal on FIO2-FIO3. Input range ±2.44V. Positive wire connected to FIO2 and negative to FIO3.

  [Analog=x]
  Device=y
  Type=Input
  SubType=Diff
  Channel=2

• Internal temperature.

  [Analog=x]
  Device=y
  Type=Input
  SubType=Temperature

• Digital input on FIO6. Positive wire connected to FIO6 and negative to ground (GND).

  [Digital=x]
  Device=y
  Type=Input
  Channel=6
  

• Frequency timer on FIO4.

  [Device=1]
  Name=my-LJU3-01
  Type=LJ-U3
  TimerPinOffset=4
  TimerClockKHz=100
  ....
  [Timer=0]
  Device=1
  

• Analog output on DAC0.

  [Analog=x]
  Device=1
  Type=Output
  Channel=0