Floating Nodes While Trying to Connect Filters in Orcad Analog Circuit Design

I'm currently working on a final project involving a Galvanic Skin Response analog circuit and I am using Orcad and pspice to troubleshoot issues with my circuit.

I am connecting a high pass filter with a cut off frequency of 0.5 hz to a low pass filter with a cut off frequency of 5 hz. I am using a Vsin source running a frequency of 2.5 hz and a voltage of 9V ac. The ground is connected in series to the source on the bottom, while the filters are connected in series on the top.

For some reason, while I am trying to run a time transient I keep receiving floating node errors after the first filter which runs in series to the second filter and then back through the ground and the source.

I have tested both filters separately and have found the amplitude of the voltage dampens correctly when non-passable frequencies are sent through the filters respectively.

I have also tried connecting a 100M and 100G resistor to the ground, floating node, and in parallel to the source to account for leakage in which none of the above worked.

Is there a way to eliminate these floating node errors while keeping the integrity of the filters created in orcad. I need to test that only a signal with frequency between 0.5 hz and 5 hz passes through both filters and exits to an amplifier.

What kind of ground did you connect as the circuit ground?
In what part of the circuit do you receive the floating node error (which node) ? Orcad usually shows a green round small object at that node, do you see it ?

Yes, I am using the 0CAP ground from the sidetool bar so the ground has value zero. The floating node comes right after the connection between the resistors from the high pass filter and low pass filter respectively. The others are triggered by the first floating node. I'm assuming it is from the DC drop caused by the capacitor, but I have tried to 100Gohms resistor tricks and they have not worked. Maybe I'm connecting them incorrectly?

RickySimcic said:

...but I have tried to 100Gohms resistor tricks and they have not worked. Maybe I'm connecting them incorrectly?

Click to expand...

That would be my guess. Without a schematic, all we can do is guess.

The error report should say which nodes, and you could see
what in the netlist has that connection.

If all pins have DC paths to ground as far as you can see,
check whether symbols may have properties that assign
a connectivity to some internal node that has no pin at
the symbol's schematic level (this is often found in things
like transistors that are generally assumed to have a global
body connection, but might want a more sophisticated
connection model in specific cases, in ID design tools).
Maybe you need to give the property a value like gnd!
to get (say) a global ground plane feature "hooked up"
to the top level.

That's my schematic-free guess (but the netlist and
error report would probably lead you to where you need
to go, if you made the effort). Grep the netlist for the
complained-about node and see how many connections,
and to what, turn up. See also if you can print a node
connections summary and see if things you think are
connected, are really connected. Maybe there's an open
in your subcircuit that you think hits a pin, but doesn't
(or a net is not "implicit" property so doesn't connect
by name the way you think, necessary to assert in some
tools, I do not use this one).

Be sure you're not looking in the wrong place, like the
floating node is really "X1.blahblah" and you're looking at
"blahblah" at the top level out of coincidental naming.

Don't trust the schematic and what you think you see. The
netlist (as boiled down - not necessarily the intermediate
one you get from schematic netlisting, but expanded with
subcircuits' text inlined) is where the floating node beefs
come from. Look there for your clues.