A single-ended -10V to +10V 16-bit data acquisition system is composed of 16 single-ended channels where two of the channels are analog outputs and the rest are analog input channels. The transducers are outputting DC-like low freq analog signals such as temperature sensors ect. Only one channel(channel 7) is carrying pulses from different types of rotating instruments. Output channels output constant voltages during the data acquisition.
The daq board is sampling at 8kHz currently and multiplexing the channels.
I'm having random glitches sometimes. By random I mean 2 or 3 times in 1000 pulses in a pulse train.
Here are some glitchy readings from the pulse channel:
Assuming signal conditioners are not causing this, what could be the problem?
Can it be realted to BNC lengths or multiplexing speed is high due to 8kHz sampling rate? Or output impedance is high? But then I'm observing this kint of glitches when it comes to pulse channel not other channels.
What could be the reason?
edit: I came across this article: http://www.ni.com/white-paper/4494/en/
At the end of it it says:
"When scanning multiple channels at high sampling rates, be careful to notice the settling time and the impedance of the source of each channel. If the source impedance is too high, charges that accumulate on the input capacitance of the DAQ device are not dissipated by the time the signal is sampled. The result of this behavior is that the signal often appears to follow the signal of the previous channel. In this situation, either the sampling rate or the source impedance must be decreased. If the sampling rate cannot be decreased, the source impedance of the signal can be decreased by using a unity gain buffer or voltage follower. When adding a voltage follower to the measurement system, be mindful of the allowable measurement error and accuracy when selecting components and the input configuration for the DAQ device. However, keep source impedances below 1 kW when sampling multiple channels whenever possible"
But I dont know it would be ralated to my issue.