I have the following reed switch sensor:

enter image description here

I need to connect this switch to counter input of this daq hardware.

The only info is the following: enter image description here

How should I connect this to the counter-input? Any diagram would help. And do I need a debouncing filter?


The relevant information is in the manual. If you intend to count the reed switch transitions you will need a debouncing circuit as the 20MHz input capability will otherwise easily pick up each mechanical bounce.

enter image description here

The design will depend on the reed bounce time (typically around a ms), the Schmitt trigger hysteresis (not specified) and the maximum frequency you wish to count at. You may have to experiment a bit.

You can try something like a 1K resistor from the reed to +5 (other side grounded) a 4.7K series resistor to the input and a capacitor from the input to ground with a time constant in the 2ms range, so C ~= 0.002/5200, maybe try 470nF X7R or film.

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  • \$\begingroup\$ I see, I want to make a Schmidt trigger with filter and hysteresis then. But my problem is what can be the min and max freq. for this reed switch for this sensor: s.campbellsci.com/documents/eu/manuals/52202_52203.pdf Any estimate? I have no experience to roughly estimate such sensor. \$\endgroup\$ – cm64 Jun 6 '18 at 10:35
  • \$\begingroup\$ The input already has a ST so an RC should be enough. Having looked at the sensor now, I doubt the tipping rain gauge can much exceed 1Hz so setting the time constant to something like 10ms (4.7uF) should easily allow the maximum frequency x10, and handle the typical bounce x5 or x10. \$\endgroup\$ – Spehro Pefhany Jun 6 '18 at 10:44

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