Hi Newer104,
Several Resistances at the Same Time
I believe you would require additional measurement devices, as the DMM can make only 1 resistance measurement at a time.
Monitoring Resistance in Real Time
If I understand correctly, then at set time intervals you want to a) measure several resistances and b) monitor them as they're measured.
Good news! You can do this with your present DMM/switch system if the timing requirements are not too tight. Use the following questions to determine your timing/synchronization requirements.
1. What is the time interval? (every minute, every 10 seconds, every second, every millisecond, etc.)
2. How exact does the time interval between measurements have to be? (to the second, millisecond, etc.)
3. How much delay can there be between one resistance measurement and another? (to the millisecond, as exact as possible with a shared backplane trigger, etc.)
(2) Note: this can be a confusing question, so I've reworded the question. "If the time interval is every minute, and my first measurement is at 0 min, do I need to measure my second measurement at 1 min (+/- 1 second), or 1 min (+/- 1 millisecond)?" The answer to this question typically determines if the program can be run on a Windows OS or if it needs to be run on deterministic real-time OS (RTOS).
(3) Note: determines if a DMM/switch system can be used to save cost over a pure DMM system. If what you need is to measure (and perhaps log/save to disk) resistance measurements and view the most recent resistance results on a user interface, then system options include:
a) one or more DMMs/measuring devices for each resistance, and
b) your current setup: one DMM and a switching front-end (to sequentially connect the DMM to each resistance one at a time)
(a) provides you with the ability to make several resistance measurements at the same time with hardware triggering
(b) provides you with the ability to make several resistance measurements at nearly the same time with hardware triggering (within milliseconds of one another), and saves you the cost of multiple DMMs
Additional RTOS Information
Read this if you require more determinism than the Windows OS can provide. Once again, the benefit here is the "exactness" of the set time interval mentioned in (2) above.
For monitoring resistance in real time, PXI controllers support a real-time operating system (RTOS). This enables you to deterministically monitor resistances at a set time interval. The way it works is you compile and download an application (such as a DMM/Switch VI you create) to a real-time series PXI controller over Ethernet. This step is actually pretty simple. In the LabVIEW project, you simply change targets from the development system (such as Windows) to the RT target and then run the VI to deploy the application to the RT machine. You can write the VI so that the RT target publishes results to the network, so you can remotely monitor the results.
Let me know if you have any trouble with the next step in your application. Feel free to start a new post, as I frequently monitor all the posts in the Switch Hardware and Software category.
Best regards,
Chad Erickson
Switch Product Support Engineer
NI - USA
Message Edited by Chad PSE on 12-01-2009 07:00 PM
Thanks Chad again! 
