We are using a PCI 4451 as an audio analyzer, and we have two different problems:
1. We want to measure the THD +N (total harmonic distorsion plus noise) for a signal.
We generate a signal of 127Hz, this signal goes through some circuits and after this, we measure the THD+N of this signal (for generating and measuring the signal, we use a PCI 4451).
We have measured the signal using an external audio analyzer and the THD+N of this is 0.05%, but using the PCI 4451 we meause 3.1%, so there is something wrong in the configuration of the audio analyzer for this frequency , but we don´t know what it is, because we are doing the same for other frequencies (100Hz, 1kHz, 10kHz) and we measure correctly with the pci 4451.
Has anyone found the same problem and some solution?
2. When we measure the THD+N for a signal of 21Hz, using a driver in labwiondows CVI that configurates the PCI4451 and measures, and it works correctly.
But when we measure this from Test Stand (that is executing the driver in CVI) is not working, and gave us a crazy value (100000000%), we thougth that it is a problem that the Test Stand execute the code more quickly and the pci 4451 dont´n have enogh time to have the correct configuration and measurement. We have added some delays but without any improvement.
Has anyone any idea?
Thanks in advanced!
Best regards,
Graci
