Signal Conditioning
how to use extract single tone information to detect the phase difference between voltage and current inputs from the DAQ card
I don't know to use the Extract single tone information VI to get the phase angle between a measured voltage from the DAQ and a measured current from the DAQ. In this Block Diagram I have tried to measure the phase angle difference of 0 between the voltage and current through a resistor. Here is the block diagram:
Hello uta_ee_student,
The reason you are seeing these broken wires is a problem related to the data type outputted by the Extract Single Tone Information VI not matching the data type of your numeric indicators. In your DAQ Assistant Express VI, you are reading from two channels: one voltage, and one current. All of the information for both channels is contained in the dynamic data wire coming out of the DAQ Assistant. When you wire this to the Extract Single Tone Information VI, this VI sees that you are wiring two channels worth of data, and instead of outputting a single value for the detected phase, its outputting an array of values, where each element corresponds to the value for a each channel. To split the data coming out of the DAQ Assistant into individual channels for analysis, you should use the Split Signals Node, as I've shown in the following block diagram. You can find the Split Signals Node on the Express > Signal Manipulation palette, or by just searching your function palette for "split signals". The Extract Single Tone Information VI is a polymorphic VI, that will either output a single results if fed a single channel, or an array of results if fed multiple channels. You can manually select which instance of the VI to use by right-clicking on the icon on your block diagram, and choosing 'Select Type'. For a single channel, choose Extract Single Tone Information 1 Chan.
I hope this helps!
Travis G.
Applications Engineering
The reason you are seeing these broken wires is a problem related to the data type outputted by the Extract Single Tone Information VI not matching the data type of your numeric indicators. In your DAQ Assistant Express VI, you are reading from two channels: one voltage, and one current. All of the information for both channels is contained in the dynamic data wire coming out of the DAQ Assistant. When you wire this to the Extract Single Tone Information VI, this VI sees that you are wiring two channels worth of data, and instead of outputting a single value for the detected phase, its outputting an array of values, where each element corresponds to the value for a each channel. To split the data coming out of the DAQ Assistant into individual channels for analysis, you should use the Split Signals Node, as I've shown in the following block diagram. You can find the Split Signals Node on the Express > Signal Manipulation palette, or by just searching your function palette for "split signals". The Extract Single Tone Information VI is a polymorphic VI, that will either output a single results if fed a single channel, or an array of results if fed multiple channels. You can manually select which instance of the VI to use by right-clicking on the icon on your block diagram, and choosing 'Select Type'. For a single channel, choose Extract Single Tone Information 1 Chan.
I hope this helps!
Travis G.
Applications Engineering
Message Edited by Travis G. on 04-18-2006 11:11 AM
