Measuring DC voltage

Hi Am trying to Measure the Voltage of a 9V Battery.After disconnecting the battery the value of the voltage in the indiacator in the VI goes down very slowly instead of falling to zero immd.Am using AI sample channel.vi to get the output from the virtual channel.How can I bring it down to zero as soon as the battery is disconnected?

I´m using LabVIEW 8.0 with Real Time 8.0 and a Desktop PCs as RT Target.
In the host.vi, I have a Waveform Chart, and a cluster with four double controls to pass the values of the Frequency, Offset and Amplitude. I have created with the cluster a custom shared variable.
In the traget I have within a Timed Loop the Simulated Signal.vi and a Shared variable, double one. I have selected both shared variables to be Network-Published, and the period of the Time Loop is 1 ms.
I intend to be able to change the senoidal waveform´s amplitude and frequency while running, but I don´t get any value. I have reproduced the vi to run just under the LabView in local mode, without the RT target, and it works fine, although I can not get the frequency to mach the time...  
Any idea why my system does not work.
Simbani     

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