Slow Sample Rate using NI cDAQ 9172 Chassis

[Kenny_K]

I am having an issue where I can not get faster than 2 Hz (two samples per second) out of my NI cDAQ 9172 Chassis.

I am running an analog input task, configured in MAX.  When I start my test, I then commit the task, and then progmatically start and stop the task, so there should be very little overhead since the task has already been commited before starting.

I am reading in 8 thermocouples and one 4-20mA sensor (in the same task), which covers 3 modules (2 thermocouple, one 4-20mA).

I have tried removing the current measurement, which gave me a slight increase in performance (3 Hz).

The cDAQ can supposedly clock up to 1Mhz, I am only looking for 100 Hz or so.

I am connected via USB to the computer, and it is a 2.0 connection.

I am saving to disk via TDMS, but there was no change in sample rate even when I disabled my tdms logging.

When I disble the task, and let me loop just run, it will do as fast as the processor (Intel Core 2 duo with 3 gb of ram) can go, so I have narrowed it down to the task itself.

Am I missing a setting?

[Kenny_K]

Ok, so I dug more into the NI 9211 Thermocouple module specifications, and they state:

Conversion time................................70 ms per channel;
420 ms total for all channels
including the autozero and
cold-junction channels

So I guess I am stuck with my sample rate, unless I want to upgrade to a different module