HSC problem in delta plc

I am trying a real simple program here. I've give DPLSY instruction to Y0 and made a wire connection so that the pulses at y0 output are reverted to x0 input. I am counting the the pulses at both output y0 and inp x0.
If I use a normal counter then it's giving accurate values, but when I use a high speed counter c235 for measuring input pulses at x0 it is giving a lot higher value than actual pulses.
I am using a low frequency of 20Hz for trial purpose. What can be the issue?

Is the output a relay or transistor (solid state)? If it is a relay it may be counting all the the bounces as well.

Just a thought,
Regards,

It is relay.
if it is counting those flickers or bounces, then it should be counted by both the counters isn't it?
Ive used two counters to measure x0 pulses.
one is arbitrary counter and another is dedicated for x0 pulses only.

High speed counter inputs have quicker response time, so will see contact bounce whereas normal inputs will have some form of filtering that will reduce seeing contact bounces.

Alan

+1 Alan
Hook your output relay to an oscilloscope and you will see the bounce of the relay.
Here are some images of contact bounce.
https://www.bing.com/images/search?q=Contact+Switch+Bounce&FORM=IDINTS

Regards,

Thankk you so much..
All I need is a transistor model to test this program onto. there wont be a problem like this in transistor models isn't it?

The transistor output model will work as you expect.