Target response tester

[green]

Trying to simulate a log decay in spice with ability to add noise and or offset to the original signal. Couldn't find a log amplifier in spice. One possibility is make one. Another option? Think the simulation decay trace is correct but the Y scale is log instead of linear. Simulation has +-5mv of noise with zero offset. Change V2 to change noise and offset. Thinking decay trace isn't going to be any better than what I'm doing now. Is the simulation decay trace correct or am I missing something? The zip file opens in my computer but not here. Running security scan never stops. Anyone know why?

[green]

Trying to simulate a log decay in spice with ability to add noise and or offset to the original signal. Couldn't find a log amplifier in spice. One possibility is make one. Another option? Think the simulation decay trace is correct but the Y scale is log instead of linear. Simulation has +-5mv of noise with zero offset. Change V2 to change noise and offset. Thinking decay trace isn't going to be any better than what I'm doing now. Is the simulation decay trace correct or am I missing something? The zip file opens in my computer but not here. Running security scan never stops. Anyone know why?

Tried to open a file from another thread, same problem. Guessing maybe the last computer update is causing the problem. I'm computer stupid, any suggestions where to look or what to try? Another question, how to do multiple passes on one screen in spice. Example: TRT_5, V2 offset -5mv, 0mv and +5mv on one screen. TRT_5, V2 used 5mv noise, zero offset in spice example. About the noise level I get at amplifier out, don't know if 5mv is good or bad. Including some scope pictures of amplifier out, scope on peak not sample. Wondering if they are what I should expect or should I be able to lower the noise level. Still want to try a log amplifier, just trying to learn something and what to expect.

[Skippy]

If you're wanting proper discrete log amp circuits for your simulation, here's a couple of Nat Semi app notes that cover the basics. Issues like temperature stability won't matter, as your simulation won't vary with temperature.
http://www.ti.com/lit/an/snoa575b/snoa575b.pdf
http://www.ti.com/general/docs/lit/g...b&fileType=pdf

[Sean_Goddard]

Eric, you need a GOOD, A N A L O G U E storage scope for best results . That digital crud is hopeless for applications like this unless you remortgage and spend the lot!

Also, notice the "rotation" of the trace. the first part of the decay is faster with the silver coin and the lower part is "extended" the reverse is true with iron, the top part is NOT rotated. Putting in an ealy sample is how I got my PI to discriminate (I used a number of sample and holds feeding comparators. I had to use some FETs as pots as some comparators required references which increased with disc level and others decreased with disc level, also some were logarithmic and some linear. Sorry I can't say which ones on here but I'm looking at a patent on this at the moment.

I have one of these; http://www.controlelectronics.com.au...0a-images.html (cost me £5000 15 years ago) might be selling everything in my lab soon so watch the For Sale section here.

[Skippy]

If you're wanting to import a Spice model of a proper log amp (rather than the photodiode-specific ones) a good choice would be the TI LOG104. The part is expensive, but the simulation is thankfully free.
http://www.ti.com/product/LOG104

[green]

If you're wanting proper discrete log amp circuits for your simulation, here's a couple of Nat Semi app notes that cover the basics. Issues like temperature stability won't matter, as your simulation won't vary with temperature.
http://www.ti.com/lit/an/snoa575b/snoa575b.pdf
http://www.ti.com/general/docs/lit/g...b&fileType=pdf

Tried building the log amp in spice. Worked but to slow. Tried downloading LOG104 spice. Computer isn't working like it was a couple days ago. I'm not a computer person, when it works fine when it doesn't I'm lost. Thanks for the suggestions, I'll keep trying to get a spice model that works.

[green]

Tried building the log amp in spice. Worked but to slow. Tried downloading LOG104 spice. Computer isn't working like it was a couple days ago. I'm not a computer person, when it works fine when it doesn't I'm lost. Thanks for the suggestions, I'll keep trying to get a spice model that works.

Wasn't thinking. Increased the RC time constant and lowered the offset frequency reply #16, input to log amp I made in spice. Log amplifier out trace(linear Y)scale close or same as log out trace(log Y)scale simulation reply#16.

[green]

Wasn't thinking. Increased the RC time constant and lowered the offset frequency reply #16, input to log amp I made in spice. Log amplifier out trace(linear Y)scale close or same as log out trace(log Y)scale simulation reply#16.

I replied running security scan never stops. Not sure that's true. Before, running security scan took a second or two. Now the zip file has come up a few minutes latter. Any suggestions why things have changed?

Including log amplifier model. Is anyone else having a problem opening the zip file?

The file did come up a few minutes latter.

[Qiaozhi]

I replied running security scan never stops. Not sure that's true. Before, running security scan took a second or two. Now the zip file has come up a few minutes latter. Any suggestions why things have changed?

Including log amplifier model. Is anyone else having a problem opening the zip file?

The file did come up a few minutes latter.

I could download and open the zip file without any problems. My Linux virus scanner shows no threats.

[KingJL]

I could download and open the zip file without any problems. My Linux virus scanner shows no threats.

Same here for Windows 10... no problems!

[6666]

I replied running security scan never stops. Not sure that's true. Before, running security scan took a second or two. Now the zip file has come up a few minutes latter. Any suggestions why things have changed?

Including log amplifier model. Is anyone else having a problem opening the zip file?

The file did come up a few minutes latter.

No problem with AVG or unzip

[green]

Thanks for the replies on the zip file opening. Some thing must have happened to my computer.

[Ferric Toes]

Eric, you need a GOOD, A N A L O G U E storage scope for best results . That digital crud is hopeless for applications like this unless you remortgage and spend the lot!

Also, notice the "rotation" of the trace. the first part of the decay is faster with the silver coin and the lower part is "extended" the reverse is true with iron, the top part is NOT rotated. Putting in an ealy sample is how I got my PI to discriminate (I used a number of sample and holds feeding comparators. I had to use some FETs as pots as some comparators required references which increased with disc level and others decreased with disc level, also some were logarithmic and some linear. Sorry I can't say which ones on here but I'm looking at a patent on this at the moment.

I have one of these; http://www.controlelectronics.com.au...0a-images.html (cost me £5000 15 years ago) might be selling everything in my lab soon so watch the For Sale section here.

Basically, I grew up in an analogue world and have mainly used analogue scopes,. However, I am pleased and surprised by what I can do with the Picoscope 2206B that I have had since Monday. The 50MHz bandwidth is more than adequate and I can switch in a variable brick wall filter to 500kHz and get a very clean picture, or alternatively enhance the waveform with a range of settings from 8 bit through to 12 bit. Appears as clean then as an analogue scope. Persistence setting allows recording the waveform change for a quarter when increasing the TX width from 200uS to 1mS. I then save a picture, convert to a .jpg ready for posting.

Still lots of features to explore and all for £299 which I think is a bargain.

Some pictures will follow when I have explored further.

Eric.

[green]

Wanting to do three scans on 1 screen. Change V2 to show difference with input offset on same screen. Amplitude and frequency=0 all three runs. Display logout with DC offset=1mv, 0mv and -1mv for the three runs. Can someone show me how?

[green]

Wanting to do three scans on 1 screen. Change V2 to show difference with input offset on same screen. Amplitude and frequency=0 all three runs. Display logout with DC offset=1mv, 0mv and -1mv for the three runs. Can someone show me how?

Haven't figured out how to do it so I pasted some traces into paint and added a straight line to simulate no offset. Looks like +-1mv input offset would be acceptable.