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DT9857E-8: Spikes in both analog outputs



One of our DT9857E-8 (8 input channels, 2 output channels) has begun to show spikes in the output signal.

To demonstrate the problem, here is a time course of a 10 Hz signal generated by the faulty DT98957E:


The sine signal has been digitally generated by our software, sent to the output in continuous mode and recorded by one of the input channels of the same DT9857E. There was only one BNC cable directly connected between the output and the input. Both outputs of the potentially faulty DT9857E exhibit this behavior.

For comparison, here is a time course from the same setup with another (known-good) DT9857E:


And FFT spectra for both signals:



Both cards were tested in the same setup.

We could partly reproduce the error in QuickDAQ. Selecting a fixed waveform output, Signal Type Sine, the resulting time course looks clean. However, selecting Sweep output, e.g. with Sweep On Time of 10 seconds, Start Frequency of 10 Hz, End Frequency of 100 Hz, the spikes are visible in QuickDAQ, as well:


To me this looks like a potential problem with the output buffer of the DT9857E.

Thanks in advance for your help!

Best regards,
Marvin Rust

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Thank you for the test results. It looks like there is an issue with the output circuitry. Please private message me with your contact information, device serial number, and sales or purchase order number. 

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