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SM70-J-T20 Hi Speed Counter Input

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Good evening.

What I have is a SM70-J-T20.  We are using it has a Batch Counter with two inputs and one output.

See attached PLC file and Drawing.

Input I:8 is used for a forever counter, never resets till it reaches the 8th digital.

Input I:9 is used for the Batch Counter and when reached a preset number will activate the Output (sprayer).

The problem.  I need to convert I:8 into a Hi Speed Input and wire it accordingly.  I need help with that.

I did leave the original counter and sensor has a backup if we lost the HMI/PLC.   The original sensor is unknown but it is a PNP.  The new one for the I:8 input is a Sick PNP IME18-05BPSZC0S.   When looking at the counters the new counter falls behind in count, example after a week of running the new sensor will fall behind about 1 feet.  We are counting in feet on our press.  SO over time it will continue to fall back.

The two sensors are mounted on the same bracket but separated about 1 3/4" inches from center of each other.  Because they are unshielded. 

Thank you




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How fast are the inputs counting?  What is the Pulse duration?

Input 8 and Input 9 are NOT  meant to be High Speed Counters.

      ( True  - they can be used for Very Slow Counting applications with long input signals)

Inputs 0-1, 2-3, 3-4   ARE the High Speed Inputs.  These Inputs can be Normal Inputs  OR High Speed Inputs

High Speed Inputs are set up in the Hardware Configuration.

Look in Help   -- High Speed Counters   - to see how to set them up and the explanation of each option available.

Change you wiring to the High Speed Counter Inputs.

Also review the Installation Sheet  provided with the PLC.



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  • MVP 2023


i do not  know your gear+sensor setup.

But main problem with counting - speed and vibration.

If you use only one  sensor and standard or HS  Input - vibration at low speed generate false pulse and counter do not count correctly (+ count error present).

If standard input used - you can lost some pulse at high speed sensor activation (- count error present). HS input in single sensor mode can be used for high speed sensor activation but start stop condition also make some count error. 

Best way for mecanical setup - use quadrature principle of measurement (you can read about it) and A/B shaft encoder HS input. Encoder with A/B output or two PNP sensor on the same special quadrature gear can be used.

This idea work with best result for low and high speed. Vibration do not affect on count result.


By the way as i see in your setup - two sensor used for mesure the same amount of data.

You can use only one sensor connected to two HS input chanel I0 + I2  at the same time and count/reset two HS counters separately.

Only one problem - HS counter backup ladder code needed. You can found V120 example in help project HSC directory.

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