03-27-2017 06:43 AM
Hi everyone,
I have some questions about sampling the quadrature signal from a HDMI port by using the PCI 6221 DAQ card and would like to have your support. Thanks!
1.Question of connection
Can i use a HDMI to BNC conventor to connect the HDMI cable and BNC cable, so i can connet the BNC port to the SCB-68 channel box. Through this connection to acquire quadrature signal?
2. Question of Counter task set up
What i am going to acquire is the signal from a interferrometer. This signal should indicate the strain difference of my object. When i use DAQ assistant, which typ of counter Input should i choose, is that Edge Count or Linear Positon?
And to acquire this quadrate signal precisely, i shoud set the clock of DAQ card faster than the clock of the HDMI interface which will be configured in the sofware of interferrometer. When i open the DAQ assistant, there this a option for sample clock type under adanced Timing, and i can only choose the "external", and have to also choose a clock source, and this step confused me. Can i use a function generator to connect to a PFI channel, and and set the frequency of the signal from function generator as a external clock?
Solved! Go to Solution.
03-28-2017 11:26 AM
1) Provided you've wired everything correctly, and someone actually makes an HDMI to BNC adapter for this, I don't see why not. The impedance mismatch may limit your maximum frequency however since HDMI is 100 ohms.
2) If it is a quadrature encoder you are reading, then you probably want linear position. Count edge may also work, but it will be less accurate since I don't believe it can use both phases of the encoder correctly.
3) You have to provide a clock that is used to read out the counter. You get one counter read per clock edge. You can route one of the onboard clocks (e.g 10Mhz reference clock) or provide your own if you want to read out synchronously with a device. The clock you provide won't affect precision however, only how often you get a position reading.