The real deal with S7-300 output speeds?

[KenE]

Hello, In the Siemens Documentation it rates the transistor output modules as being 100Hz Operation. I asked our local sales guy if there was a delay before it turned on its outputs (Which would be strange), or if you just couldn't cycle the thing on an off greater than 100Hz. He said that there was a delay, but I get the feeling he doesn't know what he is talking about. Has anyone hooked an oscilloscope up to one of these and measured what the real output latency is? You could use a single input and in code turn on the output whenever the input is true, then use the oscilloscope to measure the time between the input going true to the output going true. I don't need to have an output cycling at 100Hz by any stretch, its just incurring 5-10ms of delay per output is ridiculous for our speed requirements of a multi-operation sequential process. I should mention that I am evaluating this system, and that we don't have any "in-house" to try out. Thanks, ~Ken Edited July 22, 2004 by kemmons@qatech.com

[jacekd]

There're some delays and it's nothing strange in it. However those delays are not of 5 to 10 ms, but rather somthing like 0.2-0.3 ms (module transmission time + rising time for resistive loads). The 100 Hz limit is just switching frequency limitation probably due to heat dissipation. You can find modules with 1000 Hz limit as well. BTW, the measurement you described will give you very strange results. Because what you described is a PLC response time and it is very well defined in terms of calculation, so there's no need to measure it like this. Just refer to S7 manuals.