Target response tester

[6666]

Hi Green , sorry to put your thread slightly off track, but I was wondering if you could confirm something for me please, back when you were doing your ground balance experiments to eliminate your bags of dirt, were you simply putting the coil on top of the bags of dirt or were you bobbing the coil up and down ? thanks.

[green]

Target Response Tester wired except for log amp. Did some testing to see if it works before trying to hard wire the log amp. Finally got a silver quarter. Eric's traces of clad and silver quarters looked real close. Mine does also, closer than expected. Now to see how the log amp works if I can wire it.

[green]

Thinking about updating my target response tester to include a log amplifier and other modifications to compare with the decay curves I've been doing. Tx rate (1pps), Tx shape(constant current .5A peak or constant rate 1A peak), Tx width(adjustable 50usec to 50msec). Preamp(gain 450),post amp(gain 9). log amplifier(after preamp).

Discussion: constant current peak 1/2 of constant rate peak for same average Tx current, the lower the constant current peak the shorter the ramp time to peak, preamp and post amplifier the same as I've been using, need to modify constant rate circuit to allow adjusting Tx width while keeping 1A peak, Tx rate 1pps for low average Tx current,

Questions: any reason to make Tx rate adjustable? any changes or additions?

Comments or thoughts appreciated, would be easier to include changes now than modify latter.

Working on the bench tester. Zapped the one I've been using so the next charts or scope pictures will come from the new one. Ordered a LOG114 amp. Any changes or additions?

[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.

[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?

[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]

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

[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

[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!

[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.

[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.

[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]

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.

[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

[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.