Having a debate with by colleagues. Maybe someone can help us settle it.
Measuring upto 1000 Hz, and have the range set to 1 V on my Scadas. If there was a signal higher than 1 V and above 1000 Hz (for example, at 2000 Hz), would it cause the overload detection to go off?
Is this even important, if we are not interested in measuring above 1000 Hz?
Solved! Go to Solution.
Yes, an overload should be detected in this scenario. An overload will still be detected even if it is occurring at a frequency above your bandwidth. This is commonly referred to as an "out-of-band" overload. This happens because the channel is always sampled at a very high frequency, and then down-sampled to give the requested bandwidth. Overload detection occurs at 4 different points inside the input module, including both analog and digital locations. All of these overload detection points occur before the final down-sampling.
An "out of band" overload is still a problem for your inband data. When a signal is clipped due to overloading, it creates a broad frequency response (think of a square wave or other sharp transient signal's broad frequency content) which affects the entire frequency range. It does not matter if this clipped signal content is in the frequency range of the measurement or outside it.
That is why overload detection needs to be done at the different stages, including the analog signal. Clipping due to an overload anywhere in the chain will cause an issue.