Identification Number

The Identification Number specifies the DAQ hardware unit to configure and use. If there is more than one DAQ hardware unit on your computer's USB bus then you need to select the correct one. Normally the identification number is a serial number printed on the DAQ device, however if it is not then select a identification number, enable hardware clocking and click the Apply button. During hardware clocking the comm LED on the device looks on all the time. Once you've associated the hardware to a identification number you should probably record the identification number on the DAQ device itself. Repeat this process for all identification numbers to identify each device. You can also use the digital channel settings and monitor them, or other input or output indicators to find the device to identification number association.

Analog Input

There are 14 channels of analog voltage input labeled from 1 to 14. Channel 15 is a temperature sensor output inside the unit and channel 16 is the unit's voltage source reading. Channels 15 and 16 can help calibrate, or refactor, signals based on environmental considerations. See the Screw Connector section below for channel index to screw terminal mapping.

Analog Input States

Each channel can be turned on or off. Turn all channels off except the ones you are using by clicking the switch next to the channel number in each row. Turning off unused channels will cause the hardware to sample faster as well as eliminate spurious channel output whose values are voltage floaters (have no potential reference) and may appear random in the output.

Important: Analog Input indexes always start at one and are sequential so if you turn off a state then higher index are moved down by one. For example: If you have only Analog Input index 3 and 6 states on then those channels are remapped to 1 and 2 and are shown on the graph as curve 1 and 2, etc. and the device appears to have only two channels (as many as are turned on).

Analog Input Gain

There are 14 channels of analog voltage input each with their own gain setting. The Gain controls a pre-amplification of the signal before digitization. The gain is post-decreased after the digitization so that the recorded voltage is invariant with respect to the gain setting. The gain does affect the effective resolution of the signal and as a consequence decreases the dynamic range of the channel and is especially important for low voltage (millivolt) signals. Make sure that the gain settings will not cause the voltage to amplify greater than 5 volts (the limit of the hardware input voltage). There are 8 gain settings: 1, 2, 4, 8 both unipolar (0 to 5 volts) and bipolar (-5 to 5 volts) designated by U-1, U-2, U-4, U-8, B-1, B-2, B-4, B-8 in the user interface.

Clocking

If you choose to use the high-speed hardware clocking then the Samples per second entry is used instead of the sample interval on the main window. In addition, because it is hardware clocked the timebase increment is uniform and will not depend on the host load. Non-hardware clocked data has a timebase variability of a few percent, which is not a problem because the time at each point is recorded and is not assumed uniform anyways. Hardware clocking requires a dedicated USB device so make sure to turn off the feedback, digital and other options which can disrupt the data flow.

The Pro hardware has a limit of 50,000 samples per second. As such the Samples Per Second Per Channel times the number of analog input channels on should not exceed 50,000. For example: with one channel on the Samples Per Second Per Channel can be no greater than 50,000. With 5 channels on the Samples Per Second Per Channel can be no greater than 10,000. Other limiting factors are USB bus load and type, computer type and output state. The actual Samples Per Second obtainable may be less than the 50,000 limit.

Special Notes: There are a few limitations in streaming mode. Generally you must be aware of the following:

• Streaming channels should be turned on consecutively. For example: streaming only channel 2 and 3 is OK, but not 2 and 4.
• Streaming should be in multiples of 2.
• Streaming at high clock rates and high computer load on a slow computer may produce communication backlogs that exceed the internal buffers.

Always verify that streaming has reasonable efficacy before settling on a streaming configuration. Streaming efficacy will depend on your computer and USB bus hardware as well as the load you place on your computer.

Screw Connectors

Use the following Input Screw Connector Key to determine which channel goes with which screws. See Connectors for additional information.