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--- In LTspice@..., "Suusi M-B" <smalcolmbrown@...> wrote:

I have added EC81 and 6R4 to the Koren_Tubes.cir library see the message
49829


Suusi Malcolm-Brown

WOW, You are sooooooo good to me :-), thanx ....

best regards Leo ...

OK Helmut,
many thanks

--- In LTspice@..., John Woodgate <jmw@...> wrote:

In message <j54t57+aisu@...>, dated Sun, 18 Sep 2011, Tony Casey
<tony@...> writes:

I've uploaded to File>Temp a screenshot of what you need to change to
banish your greys.

Thank you. Yet another hidden wonder!
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

Confucius say: Things remain hidden mostly for want of looking. :-)

In message <j54t57+aisu@...>, dated Sun, 18 Sep 2011, Tony Casey <tony@...> writes:

I've uploaded to File>Temp a screenshot of what you need to change to banish your greys.

Thank you. Yet another hidden wonder!
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

In message <4E75F5EB.8040605@...>, dated Sun, 18 Sep 2011, Ganesan <dg1@...> writes:

Thanks.. i think some tubes used to carry plate current curves for different heater powers.. If going to 5.55 volts instead of 6.3 doubles
the tube life, very few wouldn't do it..

The loss, and increased variability between samples, of performance is quite significant, and longer life is not assured, because 'cathode poisoning' (contamination by outgassed contaminants) is more of a problem at lower cathode temperatures.

The best way of lengthening life is 'keep it cool and limit the switch-on surge in heater current'.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

In message <[email protected]>, dated Sun, 18 Sep 2011, Suusi M-B <smalcolmbrown@...> writes:

In the real world there is quite a difference between individual valves of the same type

They are a sort of FET, after all! (;-)
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

Kudos Tony,

Your response is extremely well written - clear and lucid,
employing a keen understanding of the minutiae of LTspice to
thoroughly answer Landrum's somewhat veiled request. Bravo for
for correctly using the b-source time step control parameters,
tripdv and tripdt - most people miss that. -- a.s.

PS: Got your email regarding the improvement of Help. I am going
to be incommunicado for a few days, but anyway I wanted to wait
to see what response Lewis gets from Mike regarding permission
to copy the existing Help to the LTwiki as a foundation upon
which to build our own expanded Help colossus. :)

--- In LTspice@..., Tony Casey wrote:

--- In LTspice@..., Landrum Haddix wrote:

I've been measuring lots of ripple voltages on DC power supply
voltages. Is there a way to get a waveform showing RMS AC volts
regardless of offset.

You questions are somewhat ambiguous, since there is no such
thing in this context as an RMS AC waveform.

If you just want to look at the AC portion of the waveform in
the viewer, you have several choices:

- Change the Y-axis plot range to only show the portion of the
waveform, you're interested in. This method has the disadvantage
that every time the viewer re-plots, it will autoscale so you
will have to repeat the scaling exercise. An alternative is to
save a .plt file with your preferred axis settings, and reload it
each time the waveform is re-plotted. Hint: assign a Hotkey to do
this. I use [spacebar] like others have mentioned recently.

- Plot the quantity V(ACnodename)-DCOffset (where DCOffset is
the numerical value for the estimated offset.

Of necessity, this will be a manual process, as the waveform
viewer has no way of knowing what you mean it to plot.

When the occasional need for this operation arises, my method
is to zoom in on either an integral number of cycles or a large
number of non-aligned cycles and ctrl-left-button click on the
trace label to read the average value of the trace. I then edit
the waveform expression to subtract this exact amount.

Alternatively, you can carry on doing it your way, but with the
same advantages and disadvantages as AC-coupling with a real
scope.

If you actually want to measure the rms value, as suggested by
the title of your post, you can use post-processing scripts to
calculate that from the simulation data.

Add the following lines in a SPICE directive:
.meas TRAN Vavg avg V(out); calculates the DC offset
.meas TRAN Vrms rms (Vavg-V(out)); calculates rms after
substracting the average

You will find the results of these calculations in the logfile
after each simulation. Of course having found the average value
by this means, you can then substitute its value into your viewer
plot expression. This is helpful since if you are also performing
a .stepped simulation, the Waveform Viewer won't calculate the
average and rms values of a waveform.

One more tip: if the AC voltage is small compared to the DC
offset, you will also need to add the directive:
.option plotwinsize=0

...too, or the waveform compression will distort the ripple
voltage and the rms calculation will be wrong.

There's also a really nerdy way to display exactly what you want
to see in the waveform viewer, but it requires some subterfuge,
and can only show the ripple voltage right at the end of your
tran time, since it calculates the DC offset on the fly. This
will only work if your DC offset is stable over time. You can
find this example as RMS_Value.zip in Files>Temp

<snip>

Yes, that's what I meant. Time to upload, clearly. See the zip archive
Pos and neg doubler rectifiers.zip It looks better if you 'Tile
vertically', which the .plt file apparently doesn't save.
--

</snip>
Hello John,

I've uploaded to File>Temp a screenshot of what you need to change to banish your greys.

Regards,
Tony

Thanks.. i think some tubes used to carry plate current curves for different heater powers.. If going to 5.55 volts instead of 6.3 doubles the tube life, very few wouldn't do it..
cheers
AG
In the real world there is quite a difference between individual valves of
the same type

The model that I created was derived from the Phillips / mullard 1968 book
graphs. There is no provision for varying the heater voltage. The heater is
assumed to be 6.3 volts DC or 6.3 volts AC (rms) No model is perfect, just
an approximation that is good enough.

The model was derived from the plate current vcs plate voltage graph for
different grid voltages. Using the below data points. The data points are
loaded into a matlab solver and the model generated.

Vplate = [ 50 50 50 50 50 100 100 100 100 100 100
150 150 150 150 150 200 200 200 200 200 200 250 250 250
250 250 300 300 300 300 300 300 300 300 ];

Vgrid = [ 6 4 2 0 -2 4 2 0 -2 -4 -6
0 -2 -4 -6 -8 -2 -4 -6 -8 -10 -12 -6 -8 -10
-12 -14 -8 -10 -12 -14 -16 -18 -20 -22 ];

Iplate = [ .0345 .026 .0185 .010 .004 .044 .035 .024 .015 .0073 .0025
.0415 .030 .020 .0118 .006 .048 .037 .026 .0175 .0105 .007 .043 .0325 .023
.0152 .0095 .050 .0388 .029 .021 .014 .009 .0055 .003 ];

Hope that answers your questions.

Suusi Malcolm-Brown

--- In LTspice@..., John Woodgate <jmw@...> wrote:

In message <j54n5o+ehah@...>, dated Sun, 18 Sep 2011, Tony Casey
<tony@...> writes:

But then, life is short...

YTM; I'm trying to do 3 months accounts for the VAT return!
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

I have mine this month too, but there's at least another 19days and 9.5 hrs left for me to do it. :-)

In the real world there is quite a difference between individual valves of
the same type

The model that I created was derived from the Phillips / mullard 1968 book
graphs. There is no provision for varying the heater voltage. The heater is
assumed to be 6.3 volts DC or 6.3 volts AC (rms) No model is perfect, just
an approximation that is good enough.

The model was derived from the plate current vcs plate voltage graph for
different grid voltages. Using the below data points. The data points are
loaded into a matlab solver and the model generated.


Vplate = [ 50 50 50 50 50 100 100 100 100 100 100
150 150 150 150 150 200 200 200 200 200 200 250 250 250
250 250 300 300 300 300 300 300 300 300 ];

Vgrid = [ 6 4 2 0 -2 4 2 0 -2 -4 -6
0 -2 -4 -6 -8 -2 -4 -6 -8 -10 -12 -6 -8 -10
-12 -14 -8 -10 -12 -14 -16 -18 -20 -22 ];

Iplate = [ .0345 .026 .0185 .010 .004 .044 .035 .024 .015 .0073 .0025
.0415 .030 .020 .0118 .006 .048 .037 .026 .0175 .0105 .007 .043 .0325 .023
.0152 .0095 .050 .0388 .029 .021 .014 .009 .0055 .003 ];


Hope that answers your questions.



Suusi Malcolm-Brown

In message <j54n5o+ehah@...>, dated Sun, 18 Sep 2011, Tony Casey <tony@...> writes:

But then, life is short...

YTM; I'm trying to do 3 months accounts for the VAT return!
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

In message <j54mi7+uvcb@...>, dated Sun, 18 Sep 2011, Tony Casey <tony@...> writes:

I'm sorry, I misunderstood your question because you used the word "pane" instead of "window". In LTspice, the Waveform Viewer understands "pane" to mean another set of axes within the same viewer window.

Yes, that's what I meant. Time to upload, clearly. See the zip archive Pos and neg doubler rectifiers.zip It looks better if you 'Tile vertically', which the .plt file apparently doesn't save.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

--- In LTspice@..., "Tony Casey" <tony@...> wrote:

--- In LTspice@..., John Woodgate <jmw@> wrote:

In message <j539as+b7s@>, dated Sat, 17 Sep 2011, Tony Casey
<tony@> writes:

I don't find this to be the case. By default, I grey all but the
focussed pane deliberately because it suits me,

How? I don't see any way to do that for several plot panes under one
instance of LTspice. For several instances, one plot pane for each, they
are all fully rendered, but this is a bit difficult to set up and the
presentation isn't as good as with several plot panes under one
instance.

but I'm sure the default Color Scheme (sic.) is for all the panes to be
"brighted" - you can change the assignments in Control Panel>Drafting
Options>Color Scheme>Waveform.

I don't see any option; the fully rendered pane is the one which has the
focus. Even the illustration in the Help (under Plot panes) shows this.

I also set a white background for the very reason that it works better
when pasted into documents. Ditto for the Schematic window.

I set a light grey background (like Excel), so I can use yellow and
white as trace colours. I agree that the default black is not a good
choice.

It may be that your settings have been changed at some time in the
distant past to give you the greyed-out state, but you don't have to
live with it.

I don't see any relevant setting. The only changes I made to the colour
scheme are to colour the traces like the resistor colour code and make
the background light grey.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

Hi John,

I'm sorry, I misunderstood your question because you used the word "pane" instead of "window". In LTspice, the Waveform Viewer understands "pane" to mean another set of axes within the same viewer window.

The problem you want to fix, is down to the OS, not the application. To fix your issue, you will need to change the graphics colour settings (assuming WinXP):
Right-click on desktop
Properties>Appearance>Advanced>Item>Inactive Titlebar

.. and change to the same colour as the Active Titlebar.

I don't recommend it, though, as you will then not be able to tell which application (window) actually has focus. But you could set the colours so they were very similar instead of just grey, or just make it temporary.

Regards,
Tony

John,

It occurred to me that there is a way around the problem arising when setting active and inactive windows to the same colour.

There's a registry hack that can cause the window focus to follow the mouse position (a la Xmouse), so there's no confusion (ha ha). I can't remember where to get at it directly in the registry, but the Microsoft Add-on "Tweak UI" is able to change all kinds of details like this without having to dive into the registry.

But then, life is short...

Regards,
Tony

--- In LTspice@..., John Woodgate <jmw@...> wrote:

In message <j539as+b7s@...>, dated Sat, 17 Sep 2011, Tony Casey
<tony@...> writes:

I don't find this to be the case. By default, I grey all but the
focussed pane deliberately because it suits me,

How? I don't see any way to do that for several plot panes under one
instance of LTspice. For several instances, one plot pane for each, they
are all fully rendered, but this is a bit difficult to set up and the
presentation isn't as good as with several plot panes under one
instance.

but I'm sure the default Color Scheme (sic.) is for all the panes to be
"brighted" - you can change the assignments in Control Panel>Drafting
Options>Color Scheme>Waveform.

I don't see any option; the fully rendered pane is the one which has the
focus. Even the illustration in the Help (under Plot panes) shows this.

I also set a white background for the very reason that it works better
when pasted into documents. Ditto for the Schematic window.

I set a light grey background (like Excel), so I can use yellow and
white as trace colours. I agree that the default black is not a good
choice.

It may be that your settings have been changed at some time in the
distant past to give you the greyed-out state, but you don't have to
live with it.

I don't see any relevant setting. The only changes I made to the colour
scheme are to colour the traces like the resistor colour code and make
the background light grey.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
When I point to a star, please look at the star, not my finger. The star will
be more interesting.

Hi John,

I'm sorry, I misunderstood your question because you used the word "pane" instead of "window". In LTspice, the Waveform Viewer understands "pane" to mean another set of axes within the same viewer window.

The problem you want to fix, is down to the OS, not the application. To fix your issue, you will need to change the graphics colour settings (assuming WinXP):
Right-click on desktop
Properties>Appearance>Advanced>Item>Inactive Titlebar

.. and change to the same colour as the Active Titlebar.

I don't recommend it, though, as you will then not be able to tell which application (window) actually has focus. But you could set the colours so they were very similar instead of just grey, or just make it temporary.

Regards,
Tony

Thanks,,
cheers
AG

Most vacuum tubes will work with ac or dc on their filaments ( some will
live a litle lesser under dc heating)... So the plate current is
proportional to the heat generated in the filament until maximum
emission is reached..( this is where most people use it).. Lifetime can
be improved at lower levels of heating , albeit with some loss of gain..
My question is, Whether the plate current to heater coupling is
correctly modeled through an rms function ?
Cheers
AG

--- In LTspice@..., Landrum Haddix <lhaddix@...> wrote:

Hi,
I may be missing something obvious. I've been measuring lots of ripple voltages on DC power supply votages.
Is there a way to get a waveform showing RMS AC volts regardless of offest.

I did a crude work around and temporatily place a 15pf cap in series with a 10meg resistor hanging off the node I want to measure.
I'm calling this an AC coupled 'Scope probe'. What is the regualr way to do this.

Landrum Haddix
lhaddix@...

Hello Landrum,

You questions are somewhat ambiguous, since there is no such thing in this context as an RMS AC waveform.

If you just want to look at the AC portion of the waveform in the viewer, you have several choices:
- Change the Y-axis plot range to only show the portion of the waveform, you're interested in. This method has the disadvantage that every time the viewer re-plots, it will autoscale so you will have to repeat the scaling exercise. An alternative is to save a .plt file with your preferred axis settings, and reload it each time the waveform is re-plotted. Hint: assign a Hotkey to do this. I use [spacebar] like others have mentioned recently
- Plot the quantity V(ACnodename)-DCOffset (where DCOffset is the numerical value for the estimated offset.

Of necessity, this will be a manual process, as the waveform viewer has no way of knowing what you mean it to plot. Alternatively, you can carry on doing it your way, but with the same advantages and disadvantages as AC-coupling with a real scope.

If you actually want to measure the rms value, as suggested by the title of your post, you can use post-processing scripts to calculate that from the simulation data.

Add the following lines in a SPICE directive:
.meas TRAN Vavg avg V(out); calculates the DC offset
.meas TRAN Vrms rms (Vavg-V(out)); calculates rms after substracting the average

You will find the results of these calculations in the logfile after each simulation. Of course having found the average value by this means, you can then substitute its value into your viewer plot expression. This is helpful since if you are also performing a .stepped simulation, the Waveform Viewer won't calculate the average and rms values of a waveform.

One more tip: if the AC voltage is small compared to the DC offset, you will also need to add the directive:
.option plotwinsize=0

...too, or the waveform compression will distort the ripple voltage and the rms calculation will be wrong.

There's also a really nerdy way to display exactly what you want to see in the waveform viewer, but it requires some subterfuge, and can only show the ripple voltage right at the end of your tran time, since it calculates the DC offset on the fly. This will only work if your DC offset is stable over time. You can find this example as RMS_Value.zip in Files>Temp

Hope this helps.

Regards,
Tony

They look cool/ Thanks..
Cheers AG..

They are included in LTSPICE, just hit the insert component menu and
navigate to the "misc" folder...
.