# Calculation slew rate rise time ?

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
Hello there,
I want to make a circuit that calculates the slew rate.
How do I follow a path?
good work.

#### R!f@@

Joined Apr 2, 2009
9,783
Welcome to AAC

I use something called a O'Scope.

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
Welcome to AAC

I use something called a O'Scope.
Thanks for your response
I know him.
I just want to make the slew rate rising time circuit.

#### R!f@@

Joined Apr 2, 2009
9,783

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
You have to explain this.
I want to make a circuit to calculate the slew rate rising time. This my project.

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#### R!f@@

Joined Apr 2, 2009
9,783
OK..and ?

If you know about programing you could make a counter between two events.

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#### Papabravo

Joined Feb 24, 2006
18,094
Here is the basic idea. When the test signal rises above the 10% level you turn on an enable signal. When the test signal reaches the 90% level you turn off the enable signal. You arm a counter to start at zero and count up with a manual RESET. When the enable signal goes to logic 1, the counter stars counting, when the gate signal returns to logic 0, the present value of the counter is held until the next manual RESET.

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,090
Simplisticly:

peak detect
Valley detect
Find 10%
Find 90%
Time from 10% to 90%

Ringing can mess up results. There's time and voltage resolutions and quantization errors and accuracies.
Make an assumption that wave is periodic.
Rise time or rise and fall time?
So, you would need to do some sort of peak/valley detect without detecting the ringing.

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
Of course I know microcontroller programming.

I install ADC and measure voltage values from 10% to 90%.
Start timer when adc = Vpp * 0.1
Timer stops when adc = Vpp * 0.9

Thus, rise time is found.
Rise time is usually 5us.
Can I measure 1us with a timer?

#### Papabravo

Joined Feb 24, 2006
18,094
Of course I know microcontroller programming.

I install ADC and measure voltage values from 10% to 90%.
Start timer when adc = Vpp * 0.1
Timer stops when adc = Vpp * 0.9

Thus, rise time is found.
Rise time is usually 5us.
Can I measure 1us with a timer?
You're going to need a very fast micro to measure smaller times. The method I outlined in hardware should work up into the 100's of MHz. with readily available components.

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
The signal will not be high frequency.
signal:
Square wave and 5v.

#### Papabravo

Joined Feb 24, 2006
18,094
The signal will not be high frequency.
signal:
Square wave and 5v.
That is irrelevant to the discussion. A 10 kHz. square wave can have a rise time of 2 nanoseconds without any trouble at all. You are the one that said you wanted to measure 1 usec. or so.

#### Mehmet Salih Aslan

Joined Feb 12, 2017
6
That is irrelevant to the discussion. A 10 kHz. square wave can have a rise time of 2 nanoseconds without any trouble at all. You are the one that said you wanted to measure 1 usec. or so.
I have no idea how many seconds it will be. I'm just guessing. If nanoseconds is the microcontroller can not do that.

#### Papabravo

Joined Feb 24, 2006
18,094
I have no idea how many seconds it will be. I'm just guessing. If nanoseconds is the microcontroller can not do that.
If you have a microcontroller than can count nanoseconds between two edges then you can use it.

#### GopherT

Joined Nov 23, 2012
8,012
I have no idea how many seconds it will be. I'm just guessing. If nanoseconds is the microcontroller can not do that.
To measure rise time directly, you'll need components that are more than 100x faster than the parts you are measuring. Otherwise, you'll need an advanced techniques...

Here is a white paper from Tektronix that starts explaining it.
http://anlage.umd.edu/highspeed.pdf

#### LesJones

Joined Jan 8, 2017
3,701
You do not seem to have established the FULL specification of the device you need to build. (Or if you have you have not passed it on to forum members.) If you have not been provided with this data then you could well have already lost marks by not asking the question.

Les.