Synchronizing two analog signals (from a tachometer and accelerometer)

[tronne]

Hi

I'd like to ask you fellow LabVIEW experts out there to help me understand about synchronizing signals.

I want to acquire two analog signals, one from a tachometer where its optical transducer is pointing towards a rotating spindle, and the other signal comes from an accelerometer that is attached to a spindle holder. These two signals will be acquired using a DAQ board (NI 9201), and connected at AI0 and AI5. I read from a manual that the tachometer and vibration acquisition channels should be synchronized together.  What does synchronize in this situation means?...Does it mean that they need to have the same sampling rate and number of samples, where the numbers can be plugged in to my LabVIEW program?

Thanks a lot for your time.

[VeeJay]

Assuming that you are reading in voltages at ai0 and ai5, I think it means you will have to create a single task to acquire both the analog signals and using index array function to separate out the measurements from each device. NI 9201 has an aggregate sampling rate of 500Ks/s. so for two channels, u hv to set it at 250Ks/s and then probably use half the samples you acquired for your processing. I hope I have answered what you asked for.

In the example I have attached, just follow the train of functions to acquire multiple analog inputs.

V

[tronne]

Dear VeeJay,

Thanks so much for your reply.

You are right, I'm reading in voltages at ai0 (for the tachometer) and ai5 (for the accelerometer). From your vi example, you are using DAQmx. I'm not quite familiar with that. I use the DAQ Assistant from the Express vi on the Functions palette. I attached an image of my block diagram. As you will see, I use a split signal vi to split the signals that are generated. One will go to the Analog Tacho express vi and the other goes to the graph indicator. At this point, how do I know whether the ai0 will go to the Analog Tacho vi?...but maybe this is not important since both channels have the same sampling rate (250Ks/s) and number of samples (16384), which means both channels are synchronized, right?. So, do you think my program serves the task correctly?

Thanks.