The only information that I could find for BM analog input:  “cycle time for analog value generation is 300 ms”. No mention what does it means.

So the problem that makes me wonder (LOGO8.4):

For some not too serious project I need 8 additional keys for manual operation. I just made some simple analog keyboard– press one button the output is 1V press another the output is 2V and so on. The delay of 300ms could be OK. Of course for safe operation the some filtering should be used and the response time could even double. I configure 8 analog threshold triggers and connect 8 output relays.

I made some preliminary program test and the result was this: all threshold triggers get actuated in sequence and the output relays made audible dzzzinnn sound. When I release the button the all repeats in reverse direction. With some addition software I get the things right (with some annoying response delays) but after that I make some additional “investigations”.

I made program for logging analog input value with 10ms intervals (50 mathematic blocks in series).

I expect the response like RC filter but get the exactly linear curve. Each reading increments by 50 units (0.5V) up to the supplied voltage level. Some examples:

51-101-151-…-751-766-(766) for 0 to ~8V

51-101-151-…-651-666-(666) for 0 to ~7V

51-101-151-…-951-1000-(1000) for 0 to 24V

Sometimes I even get the same reading twice. Then I speed up logging to each cycle (about 3ms) and get the same numerical values only repeated 3-5 times.

For 3.3t to 5.7 V all readings: 334-384-434-484-534-574-(574) settling time = 60ms

Conclusions:

1. Analog value generation means changing analog value by 50 units in 10ms intervals up to supplied value.
2. So in some 200ms the full scale changes are finished (better than 300ms)
3. If only 0..5V range is used the analog value generation will takes only 100ms
4. Small changes of analog input could be tracked relatively fast 20-50ms
5. To be sure that the analog reading corresponds to the input value the approximately same value should be read by 20-30ms interval. (for may analog keypad I select 40ms - works fast and perfect)
6. If some additional buttons required in the project the analog keypad could be considered as the solution.

The anlog keypad from leftovers (assambly time less than 1h)

Try it this way. You can find all tips and explanations in the attached LOGO program. Please pay attention to the red comments!
Wishing you success, regards, Quirin
(translated with Bing)

Addendum: A new analog value is only recognized (the push button is pressed) if the value 0 (zero) was read in beforehand (the push button was not pressed).