why i am getting wrong signals

[preet]

i am acquiring dc signals of range 0-10 volts via two input channels. i am acquiring signal of -10 volt on one channel and that of +10 volt on the second. these are very well plotted on the waveform chart. but when i disconnect one of these (say -10 volt), the disconnected signal shifts to the other signal i.e. +10 volt on the waveform chart. now the two signals show the same value. what may be the reason for that.
please solve my problem..

[PdB]

What in fact you are saying is that you cannot detect a loose connection. It's an impedance problem.
When the conection get loose the input pick's up voltage signals of high-impedance values (neighbouring signals, noise or supply voltages).
An ancient solution for this solution is tying this signal with a resitor to your analog ground (the ground signal of your analog inputs). The resistor-value will depend on the output impedance of your analog sources. You could start with 100K and see if your connected measured signal drops/rises.
Detecting loose connections is one of the reasons in industrial wiring one uses 4-20mA signals, where 0 mA means a broken wire.

[preet]

thank you sir for your reply
i have got my answer