Noise data Filtering

[johnsold]

Here is the VI.

Lynn

[Munna232]

can you tell me what is the Best to solve my issue.

I want to Filter Noise data From Signal. this Noise data is very Small (sometime) .

[johnsold]

Please tell me more about the signal. The term "noise data" is not commonly used in English so I think we may have a communication issue.  "Data" is usually applied to the part of the signal which carries useful information, although it can also be used to describe the raw measurement of the total signal plus noise. The term "noise" almost always is used to describe a random component which contains no useful information.  The word "signal" - like "data" -  can be used to refer to the information component or the total of information plus noise.  There can also be "interference" which refers to a signal component which may carry information but which is not the desired information.

Let me use the term "data" to refere to your digitized measurement before any other processing.  I will use the term "information signal" to describe the part of the data which carries the desired information you wish to extract from the data. And I will use "noise" to describe the random component of the data. The image below shows a simple example.

What does your information signal look like? What are its frequencies and amplitudes? What information about it do you need to measure?

What does the noise look like? What is its amplitude?

What generates the information signal? What generates the noise?

Sometimes filters are good methods of reducing noise while in other situations different methods work better.

Lynn

[Munna232]

Dear Lynn,

Thank you so much for you help.

====================================================

What does your information signal look like? What are its frequencies and amplitudes? What information about it do you need to measure?

What does the noise look like? What is its amplitude?

What generates the information signal? What generates the noise?

Sometimes filters are good methods of reducing noise while in other situations different methods work better.

Lynn

=====================================================

My information Signal is DC type. Amplitude “5V”.

Noise Signal amplitude will change at run time (as of now it’s not fixed).

Information Signal Generated by Function Generation.

Noise Signal Generated by Hardware Switch (Simple Two-way Switch). When I’m doing switch ON & OFF some noise is adding to DC information Signal.

So, Data Signal contains both Information signal + Noise signal.

From this Data Signal I want to filter some Noise based on my Cutoff Frequency. Remaining data (after Filter) I want to display on the Graph.

I hope now this is clear for you. Please let me know if you need any other information.

Munna

[johnsold]

Munna,

If the Information Signal is DC then the easiest way to reduce random noise is to average multiple samples.

However, since you describe the noise as being generated by the action of a switch, it is possible that the noise is not random. In that case averaging might not help.  Do you just get a transient inserted into the data every time the switch changes position? Or do you get  random noise added in one position of the switch and not the other? Do you have any way to detect when the switch changes position, such as a 0 to 5 V change on a second pole of the switch?

Is the noise random or is it correlated with the action of the switch?

Lynn

[Munna232]

Hello Lynn,

Thank you so much for your help.

As of now we have connected simple Switch for Tool development. After that we are going to add More switches. So, if any of the switch operated and Noise is Generated by it, then we need to Filter it.

This Noise is Random noise and it’s not depends on one side of the Switching action.

We need to filter the Noise whenever its adding to my Information Signal (Continues Loop).

Note: FYI, as of Now, Information DC Signal Voltage is 5V. In future we are planning to increase up to 15V.

Munna

[johnsold]

Munna,

I still do not completely understand how your system is set up. What is Switch for Tool?  Can you post a diagram showing the hardware that you have (or will have) connected and what you are measuring?

Lynn

[Munna232]

Dear Lynn,

Sorry for the inconvenience caused.

My setup is Very Simple. I connected Function Generator o/p to Scope. In between I connected Switch.

If I’m not doing Switch ON & OFF then scope simply showing DC output Voltage. When switch is operated some Noise is adding to DC signal so, that time in scope I can see DC Signal with Noise.

When Noise is coming then I need to Filter based on Cutoff Freq.

I hope this is clear for you. Please let me know still you have any doubts. I will send you sample Setup Image.

Munna

[johnsold]

Munna,

I think I understand now. When the switch changes position, a disturbance appears in the signal. This is often called a "switching transient."

Typically when such transients occur it is because the signal is being switched from one source to another or from one load to another.  In cases like that the value of the signal is usually meaningless at the moment of switching. So the solution is usually to detect the switching time and simply discard the data immediately before and after the switching time. The duration of the discarded section depends on how long it takes the switch to physically change positions (including bounce) and how long it takes the circuits and signals to settle to a final value after the switch is in the new position.   This can be microseconds or less for some types of electronic switches and tens to hundreds of milliseconds for relays or power contactors.

Use of a filter in such cases can actually make things worse because the filter stores some of the energy produced by the switching transient and passes it to the output over time.

Lynn

[Munna232]

Hello Lynn,

Your understanding is correct but we don’t want to find the “Switching Transient”.

Just we want to pass same Noise along with information signal. Because output information signal we are connected to Circuit board by connecting 1^st Order RC-Filter Circuit in between.

So, our Aim is Tune R& C values to protect my Circuit board. For that we want to know up to what level Noise is filtering.

We want to compare Filtered data with Reference voltage (i.e. 25mv) . If data is more than 25mv it means some data is not filtered. In this case we will change the R & C values.

 Munna