# Circuitikz label in middle of open circuit

I've just started using Circuitikz and and I'd like to know how one would go about getting a label say, 'v', in the middle of the open circuit (perhaps with a plus and minus either side of it).

Also, is it possible to insert an ammeter or a voltmeter which don't have the diagonal line going through it?

Thanks

Edit:

\begin{circuitikz}[american, scale = 2]\draw
(0,0)       to [sV = $V_m\cos(\omega t + \theta)$]  (0,2)
to [R = \si{250}{\ohm}, *-*]            (2,0)
to [L = \si{300}{\micro\henry}]         (0,0)
(2,2)       --                                      (4,2)
--                                      (2,0)
(0,2)       to [short, *-o]                         (0,3)
(2,2)       to [short, -o]                          (2,3)
;\end{circuitikz}


-
Can you include the code that produces this image please so that we can play around with it? –  percusse May 16 '12 at 1:38
For getting voltmeters/ammeters without the arrow: tex.stackexchange.com/a/42804/2552 –  Jake May 16 '12 at 5:38
Sorry bout that, I've added the code. –  user968243 May 16 '12 at 6:21
You can directly use TikZ syntax inside circuitikz env. say \node at (1,3) {$+\; V\; -$};. Also without an arrow measurement units are simply circles hence easy to place it using standard TikZ commands. –  percusse May 16 '12 at 8:33

You should edit the voltmeter definition from the CircuiTikZ code. I did it for you by commenting some lines and adding a new line to rotate the label. Actually I created a new component named myvoltmeter, based on the original. I mirrored the inductor too. Please, use siunitx as explained in the package manual.

\documentclass{article}
\usepackage{siunitx}
\usepackage{circuitikz}
\makeatletter
\def\pgf@circ@myvoltmeter@path#1{\pgf@circ@bipole@path{myvoltmeter}{#1}}
\tikzset{myvoltmeter/.style = {\circuitikzbasekey, /tikz/to
path=\pgf@circ@myvoltmeter@path}}
\pgfcircdeclarebipole{}{\ctikzvalof{bipoles/voltmeter/height}}{myvoltmeter}
{\ctikzvalof{bipoles/voltmeter/height}}{\ctikzvalof{bipoles/voltmeter/width}}
{
\def\pgf@circ@temp{right}
\ifx\tikz@res@label@pos\pgf@circ@temp
\pgf@circ@res@step=-1.2\pgf@circ@res@up
\else
\def\pgf@circ@temp{below}
\ifx\tikz@res@label@pos\pgf@circ@temp
\pgf@circ@res@step=-1.2\pgf@circ@res@up
\else
\pgf@circ@res@step=1.2\pgf@circ@res@up
\fi
\fi

\pgfpathmoveto{\pgfpoint{\pgf@circ@res@left}{\pgf@circ@res@zero}}
\pgfpointorigin   \pgf@circ@res@other =  \pgf@x
\pgfpathlineto{\pgfpoint{\pgf@circ@res@other}{\pgf@circ@res@zero}}
\pgfusepath{draw}

\pgfsetlinewidth{\pgfkeysvalueof{/tikz/circuitikz/bipoles/thickness}
\pgfstartlinewidth}

\pgfscope
\pgfpathcircle{\pgfpointorigin}{\pgf@circ@res@up}
\pgfusepath{draw}
\endpgfscope

\pgfsetlinewidth{\pgfstartlinewidth}
\pgftransformrotate{90} % rotate the label
%\pgfpathmoveto{\pgfpoint{-\pgf@circ@res@other}{.8\pgf@circ@res@up}}
%\pgfpathlineto{\pgfpoint{\pgf@circ@res@other}{.8\pgf@circ@res@down}}
%\pgfusepath{draw}
\pgfnode{circle}{center}{\textbf{V}}{}{}
\pgfscope
% \pgftransformshift{\pgfpoint{-\pgf@circ@res@other}{.8\pgf@circ@res@up}}
% \pgftransformrotate{45}
% \pgfnode{currarrow}{center}{}{}{\pgfusepath{stroke}}
\endpgfscope

\pgfpathmoveto{\pgfpoint{-\pgf@circ@res@other}{\pgf@circ@res@zero}}
\pgfpathlineto{\pgfpoint{\pgf@circ@res@right}{\pgf@circ@res@zero}}
\pgfusepath{draw}

\pgfusepath{stroke}
}
\makeatother

\begin{document}
\begin{circuitikz}[american, scale = 2]
\draw
(0,0)       to [sV = $V_m\cos(\omega t + \theta)$]  (0,2)
to [C = \SI{10}{\pico F}]               (2,2)
to [R = \SI{250}{\ohm}, *-*]            (2,0)
(0,0)       to [L = \SI{300}{\micro H}]             (2,0)
(2,2)       --                                      (4,2)
to [myvoltmeter]                        (4,0)
--                                      (2,0)
(0,2)       to [short, *-o]                         (0,3)
(2,2)       to [short, -o]                          (2,3)
(0,3) [yshift=5pt] to [open, v=$v(t)$]              (2,3)
;
\end{circuitikz}
\end{document}


-
@percusse, if you comment the empty pgfscope, you'll get two concentric circles. –  Luigi May 16 '12 at 11:33
That's strange but I should have run the code before the edit. Sorry. –  percusse May 16 '12 at 11:44
Thanks. Is there a way to make the change permanent? (So every time I use Circuitikz, the voltmeters have no line throught them.) –  user968243 May 17 '12 at 6:06
@user968243, just open pgfcircbipoles.sty and comment lines 1049-1051 and 1054-1056 (as I did for my component). –  Luigi May 17 '12 at 10:39