Micrologix 1400 "Fast" inputs

locotumbler

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I am looking to see what is defined as fast inputs. Is this just another way of denoting HSC inputs? I am looking at the manual (1766-UM001M-EN-P) and the only reference to the word fast in the entire thing (if the find feature is to be believed) is on page 16 when talking about the inputs themselves.

Thank you in advance.
 
Code:
• Twelve high-speed inputs (except 1766-L32AWA and 1766-L32AWAA controllers) 
that can be used individually as latching (pulse-catch) inputs, event interrupts, or 
alternately combined as three 100 kHz high-speed counters featuring 10 modes of 
operation.

This came from the product selection guide. So the answer to your question is that they *can* be HSC inputs. Here is the selection guide:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1761-sg001_-en-p.pdf&ved=2ahUKEwiih_u6ytneAhWq6oMKHZCPBkAQFjAIegQIBBAB&usg=AOvVaw0wv_ROQC8AMa-h6sgh4kdp&cshid=1542394325918"
 
Yup; the first 12 inputs can be used with HSC or with interrupts for pulse-catching or discrete input interrupt features. You're on the right track !
 
Thank you. I am not looking to use them as a HSC but the 1200 I am replacing misses one of my sensor signals from time to time.

Check the base input filter settings and compare with the duration of the sensor signal. It might be that you need to adjust the base input filter to detect pulses of a shorter duration.
 
locotumbler said:
I am looking to see what is defined as fast inputs. Is this just another way of denoting HSC inputs? I am looking at the manual (1766-UM001M-EN-P) and the only reference to the word fast in the entire thing (if the find feature is to be believed) is on page 16 when talking about the inputs themselves.

Thank you in advance.

Note: On the MicroLogix 1400 models which include 12 fast DC inputs, they are also referred to as high-speed DC inputs. This may help you in finding the relevant information within the User Manual.

If you go to Appendix A (Page 167), you should find the section -

Specifications for inputs

Under which you can find the information I believe you are looking for...

Inputs 0 through 11 (12 high-speed DC inputs)
Operating frequency - 0 Hz...100 kHz

Inputs 12 and higher (8 standard DC inputs)
Operating frequency - 0 Hz...1 kHz (scan time dependent)

So the definition of fast DC inputs in this case is 100 times faster than their standard DC inputs.

The high-speed DC inputs are handled by an on-board dedicated high-speed module whereas the standard DC inputs are not. This is why the high-speed DC inputs are not affected by the program scan time.

Regards,
George
 
Last edited:

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