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How come when I try to record data all I see is a flat line?

There are many possible reasons for a flat signal. It is important to make a distinction between the data (the numbers that the computer is actually recording) and the display of the data (how the numbers are shown in the graph window). The two channels shown in the image below contain the exact same data; the lower channel is a duplicate of the upper. However, the lower channel is displayed with a much coarser scale (zoomed out).

vertical autosclae toolbutton

The first troubleshooting step is to re-scale the display of the data. There are multiple ways to do this, but one is to select the channel and click the vertical autoscale button in the toolbar.

If scaling is not the issue, the next step is to ensure that channel setup is correct.

If neither channel scaling nor channel setup is the cause of the flatline, verify that all equipment is securely connected.

Also make sure that all relevant switches are in the “On” position.

If the system has not been used before, make certain that a signal is expected under the present conditions.

If answers to all of those questions are “yes”, only then is it time to entertain the possibility of a hardware failure.

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