SIMULATIONS

[Sargon]

I'd like to ask what simulation software you guys use?

There are many Spice-based programs out there. So far, I have worked with PSpice (now Cadence OrCAD), LTSpice (free), TinaTI (free) and currently NI Multisim is my simulator of choice. There's also a low-priced student edition available. What I like about Multisim is the GUI, the large database of elements and the instruments.


Greetings and happy hunting!

Sargon

[joop]

Slightly off-topic, but... I'd like to ask what simulation software you guys use?

Judging from all the electronics simulations I see on this forum, LTspice is your friend. See http://www.linear.com/designtools/software/#LTspice
It has good documentation and an active user community at Yahoo Groups. There you can also find plenty of tutorials.

[Davor]

There is more to Fe targets than the PI Rx can show, mainly because it neglects the time zero behaviour. I made some Fe targets for simulation that are less than perfect for two reasons. I have no PI machine to compare my findings with simulation, and second, due to Spice limitations I was able to simulate a target with split personality - one side links to Tx, while the other links to Rx.
Besides, my "target" so far never crosses the 90° barrier, while real world Fe targets do at higher frequencies, where eddy currents overcome ferrous behaviour. Perhaps it would be wise to split the Fe target in simulations in several targets to achieve the obvious - dissimilar behaviour at low against the high frequencies due to completely different modes of operation.

Then we hit my problem No. 1 - I do not have real world PI samples to compare my simulations with.

[Ferric Toes]

Often the simulations do not produce quite the same output as the real component circuits. But even then they can give us an approximate idea what to expect from the real circuit.

Of course, if the simulations are different, it is because we have not taken account of all the involved factors. Therefore, we try again and after a few tries, we get closer to the real results. It is a learning process.
Learning is good, but takes time.

Could we accelerate our learning process by Crowd Sourcing PI simulations? There are a few people on this forum, with lots of knowledge. Others, like myself, are just trying to learn something.

Would the knowing ones teach the students? I hope.

How can we simulate an FE target? Let's take the response of a real target as goal. The infamous bottle top or crown cork. It is a tricky target, because it shows very different characteristics, when presented to the coil at different angles.
In the vertical position, the X response is dominant, but there is still a little R component too.
In the flat position, the R response is dominant, but the x response is still there to some degree.

If we want to find ways to perfectly discriminate this pesky target, we must fully understand the reasons for the different responses.
If we fully understand the reasons, we have a better chance to design a perfect discrimination.

Let's simulate!

Tinkerer

Let's deal with the real world first. When you scan over a horizontal steel bottle cap, you get a large change in TC. As the coil edge approaches the cap the field is parallel to the plane of the cap (X direction). The response is primarily a viscosity one, amplified by the permiability, and is a long decay. As the cap passes under the coil centre the response shifts to a conductivity one (R direction) with only a small X component, as you say. Steel is not a very conductive metal so the decay is fast. This can be seen quite nicely by taking an early sample and a later sample and dividing the early by the late. This gives a result that is virtually independent of amplitude but changes for different TCs. A horizontal non-ferrous coin will give a constant reading dependent on conductivity, while a ferrous bottle cap will give a variable reading as scanned. Vertical bottle cap will reverse the responses but you will still see a change.

Eric.

[Pete the Builder]

Slightly off-topic, but... I'd like to ask what simulation software you guys use?

I've been looking around for software to run on my Macbook Pro, but the few (4 or 5) open source (i.e. free) simulators all have pretty steep learning curves.

There's more available for Windows (I have a number of very high-end Windows machines that are perfect for simulation), but that just complicates things!

I have Protel DXP (version 7.0), which has great Spice simulation, but it's a real handful to get configured, especially since I use many non-standard library devices, many of which have no Spice model attached. I feel like a Cessna pilot sitting in the cockpit of an FA-18 fighter, looking for the key!

If anyone could perhaps point me in the direction of a good simulator package that a new user could use to get started, and perhaps that others here use, it would be much appreciated! The more common the better, at the moment - this would allow a lot of interchange between members. If that's on anyone's priority list!

I don't mean to hijack this thread, so PM would be acceptable if it doesn't detract from the real purpose of this thread.

Sorry for the interruption. Normal service will resume in 3...2...1...
PtB

[Tinkerer]

Often the simulations do not produce quite the same output as the real component circuits. But even then they can give us an approximate idea what to expect from the real circuit.

Of course, if the simulations are different, it is because we have not taken account of all the involved factors. Therefore, we try again and after a few tries, we get closer to the real results. It is a learning process.
Learning is good, but takes time.

Could we accelerate our learning process by Crowd Sourcing PI simulations? There are a few people on this forum, with lots of knowledge. Others, like myself, are just trying to learn something.

Would the knowing ones teach the students? I hope.

How can we simulate an FE target? Let's take the response of a real target as goal. The infamous bottle top or crown cork. It is a tricky target, because it shows very different characteristics, when presented to the coil at different angles.
In the vertical position, the X response is dominant, but there is still a little R component too.
In the flat position, the R response is dominant, but the x response is still there to some degree.

If we want to find ways to perfectly discriminate this pesky target, we must fully understand the reasons for the different responses.
If we fully understand the reasons, we have a better chance to design a perfect discrimination.

Let's simulate!

Tinkerer