Maximum I/O Signal Rate for NI 9361

Issue Details

• I want to use NI 9361 to do encoder acquisition and I want to know the maximum pulse input limit corresponding to my encoder.
• When I was looking at NI 9361 specifications, it is stated that the I/O signal rate is 1 MHz maximum. However, when I did a quick test on my side, the NI 9361 was still able to detect a 5 MHz frequency correctly. So, what is the maximum frequency that can be measured by NI 9361?

Solution

I/O signal rate is the maximum frequency of the input signal to be measured and for NI 9361, it is specified at 1 MHz. The reason it is specified at 1 MHz is because when the device measures beyond 1 MHz, the front-end circuitry will cause degradation to the signal rise and fall time that might impact the accuracy of certain measurements such as duty-cycle. In reality, since the counter timebase is 100 MHz, it can still measure I/O signal rate beyond 1 MHz though the measurements might no longer within the device specification. 

Therefore, when using NI 9361, it is highly advised to set the maximum I/O signal rate to 1 MHz as per stated in the specification.