In the project tree, expand your PLC (you probably already did this).

Double click the device configuration.

In the bottom pane, click "Properties" tab, and "General".

In the left side of that pane, find your digital inputs.

Expand the digital inputs to show them all.

Select the one you wired to.

Adjust the input filter.

--- you need to look at your hardware settings... click on the help when you want to know more.

Writing plc logic without understanding something about the hardware configuration is going to cause you problems when you least expect it, like trying to get a frequency from pulse trains faster than the input filter.

bruno_cardoso

I wired it in the I0.4 input of the CPU (Sorry I forgot to say this).
I know this is bad but how do I set the input filter?

Thanks

Did you change the input filter time, compile and download the hardware changes to the PLC and try it?  What happened?

bruno_cardoso

I already start to feel this difficulty and that is why i asked for help, because alone I would not be capable to understand why is not working. Thank you for the help you are giving me.

On the sensor characteristics there is an information that says: - Filter: < 50Microns

Is this the condition that I have to fulfill? Sorry for all this questions but when I google it, what appears to me is that this is a measure of length and not time.

Thank you a lot

When you go online with the plc and monitor the norm/scale blocks for your frequency measurement, have you tested the scaling and looked at the values to see if they match?  For example, if the flow rate is known and measures 1 L/min, does the PLC scaling block output show 1 L/min?

If not, you may need to adjust the values.

bruno_cardoso

Hi,

I changed the input filter to the lowest available possible and I download it to the PLC.

However, it's appearing the "-1 L/min" on the HMI that I used (the L/min is the units that i selected in the hmi variable).

I do not know what is happening wrong.

If you have a function generator, you can send pulses to the HSC input and verify it counts.  If not, you can use a manual switch to see if the counter is counting at all.   Use the worst bounce button you can find to get many pulses per button press (cheap buttons have horrible bounce).

Is it possible your input or scaling tags are used in multiple places or have memory overlaps?

If you have a relay you do not mind wearing out, you can use a PLC output to drive a relay for testing.  Toggle it at different speeds to simulate different flow rates and wire a contact between your 24v supply and the input.

Oh yes, is the counted signal changing from 24V to 0V?  If not, that is the problem right there.

bruno_cardoso

Hello ,

I apologize for taking to long to say something but I encountered other great difficulties in the program that I was trying to solve.

I tried what you suggested and monitor the values of the Norm and Scale functions. For a flow rate of approximately 3L/min, the values were completely wrong and I do not know why. In the input of the Norm_X function the value which appears is 0, while the value of the output (which is the input in the Scale_X) is -0.071.

Is the HSC not working properly? Or did I connected it the wrong way?

Thank you for all the help

An oscilloscope, voltmeter with very low flow rates.

If you look at the specifications for the sensor, it if says it switches between 0 and 24V, then verify the pins are correct.

If you want your system to run, sometimes you have to abuse a used relay even further to test things.

Hopefully you have an o'scope and can measure the signal.  Some o'scopes will display the pulse train frequency for you and then it is easy to know if the pulse train is correct.

To troubleshoot knowing the input is correct is a lot simpler.

It is wiring, configuration, both, or looking at the wrong value (programming)

Can you do a screen shot for the following:

Schematic drawing for the PLC input that is the frequency input.

PLC hardware configuration for digital input it is wired (for filter setting)

PLC hardware configuration for the HSC configuration used

Picture of the wiring on the PLC where the sensor signal was measured with the o'scope.

If you toggle the HSC from frequency to counts, does it begin counting?

Are you reading the input directly?  Like ID1000?

Look at that value and if it is changing in relation to the changes at the input, then it is programming.  If it is not changing, it is something else.

bruno_cardoso

Hi huggy_d1,

I used an osciloscope to measure the flow rate sensor signal and it showed me a square wave changing from 0V to 24V, as expected, with a frequency of more or less 275Hz. However, the variables from the program were showing 0.

I probably have some program problem, is not right?

Thank you for your help

The images are most helpful.

1. PLC wiring: The M terminal closest to the left of I0.4 is your DC common reference for the signal input.  It is not wired.  That will keep things from counting properly.

2. The PLC logic and hardware wiring do not match.  I0.4 is not ID1000 unless you manually changed them.  The default for I0.4 as a HSC is ID1008.

If you wire your PLC digital input M to DC common, monitor ID1000:P in the PLC, then store it to a tag located in the M area, like MD50, then point the HMI to MD50, you will have better luck.

Having the HMI read the input port directly is not something you should do.

bruno_cardoso

Hi,

Yes, I am using the ID1000:P (I do not know if I should be using the ":P" but I read in the forum that it allows the immediate reading). 

However, the value of this variable that appears in the HMI (I put it as you suggested) is 0.

I also changed the HSC from frequency to counts and even then the value of the "ID1000:P" is 0.

This means that is probably some configuration problem, is it not?

The screen shoots that you asked are in the attachment. Thank you for all the help that you have been giving me