How do you connect separate VIs so data can be read in one and displayed in another?

Question

I am reading data from a Lock-In Amplifier. I have wrote a general VI for the Lock-In Amp. I need to transfer data from this VI to a Control VI which logs the data. The Control VI also has to read temperature readings from a Temperature control VI. All three VIs will be running on the same PC.
The VIs must remain separate. The Control VI cannot read from the Lock-In Amp or aquire the temperature readings. Do you use ActiveX? If so, how?

Answer 1

There are three relatively straightforward methods that come to mind, though the best implementation will depend upon the amount and rate of your data transfer.
1) Queues
Create a named queue, containing the appropriate data type(s). Add elements to the queue in the "Lock-In Amplifier" VI and remove elements from the queue in the general VI. This method may be the easiest to implement since all of the data handling mechanisms to ensure that data isn't lost or duplicated are built into the queue functions.
2) Datasockets
There are plenty of examples for transferring data via datasockets. I haven't used them as often as queues, but they're definitely the best choice in some circumstances.
3) By Reference
Create a reference in your general VI and pass th
e reference to your "Lock-In Amplifier" VI in the process of calling it. Alternately, the reference could be stored as a global variable so that the programs could be started independently. The "Lock-In Amplifier" VI would then utilize a property node to write data to the referenced memory. Of course, this method would require polling and a mechanism for preventing data from being lost. This wouldn�t be my first choice method.
Certainly there are other methods as well, but I hope this gives you a good start.