with nothing physically connected on the input:
AC or DC -->
+-20V A_ch=-0,449V; B_ch=-0,445V;
+-10V -0,225V / -0,224V;
+-5V -0,115V / -0,107V;
+2V -0,042V / -0,031V;
+-1V -23mV / -23mV;
+-500mV -11mV / -11mV;
+-50mV -1,2mV / -0,85mV;
auto -1,2mV / -0,86mV;
????