POTENTIOSTAT REFERENCE ELECTRODE INTERFACE
A method for shielding an electrical signal without substantially degrading the system speed or substantially increasing the bulk of the system is provided. The method includes applying a first signal to a conductor coupled to the electrode, applying a second signal to a shield substantially surrounding the conductor, blocking electrical interference to the first signal, and increasing an effective impedance on the electrode coupled to the conductor. The second signal may be a buffered and compensated version of the first signal.
1 . A method implemented by a circuit for shielding an electrode from interference, the method comprising:
applying a first signal to a conductor coupled to the electrode;
applying a second signal to a shield substantially surrounding the conductor;
blocking electrical interference to the first signal; and
increasing an effective impedance on the electrode coupled to the conductor.
2 . The method of claim 1 , wherein the second signal is a compensated version of the first signal.
3 . The method of claim 1 , wherein the second signal is buffered.
4 . The method of claim 1 , wherein the second signal is created using compensation circuitry.
5 . The method of claim 4 , wherein the compensation circuitry is configured to:
measure the first signal on the conductor;
amplify the first signal;
remove at least one high frequency component from the first signal; and
phase shift the first signal.
6 . The method of claim 1 , further comprising substantially reducing a potential difference between the conductor and the shield.
7 . The method of claim 6 , wherein substantially reducing a potential difference between the conductor and the shield comprises reducing the potential difference to approximately zero.
8 . The method of claim 1 , wherein the second signal is applied by a low impedance source.
9 . A method for detecting a target in a sample using a point-of-care diagnostic device, wherein the diagnostic device includes a potentiostat that uses the method according to claim 1 , thereby providing active shielding for one or more reference electrodes in the potentiostat.
10 . The method of any one of the preceding claims claim 1 , wherein the signal path comprises a reference electrode in a potentiostat.
11 . The method of claim 1 , wherein the signal path comprises a high impedance transducer interface.
12 . A signal transmission system comprising:
a transmission line including a conductor and a shield substantially surrounding the conductor;
first and second compensation circuits coupled between the conductor and the shield; and
a unity gain buffer coupled between the first and second compensation circuits.
13 . The signal transmission system of claim 12 , further comprising an electrode coupled to the conductor.
14 . The signal transmission system of claim 13 , wherein the electrode is a reference electrode.
15 . The signal transmission system of claim 12 , wherein the first compensation circuit reduces high frequency gain to reduce positive feedback caused by coupling in the shielded transmission line.
16 . The signal transmission system of claim 12 , wherein the first compensation circuit provides phase shift to reduce positive feedback caused by coupling in the shielded transmission line.
17 . The signal transmission system of claim 12 , wherein the second compensation circuit phase shifts the first signal to reduce positive feedback caused by coupling in the shielded transmission line.
18 . The signal transmission system of claim 12 , wherein the transmission line is a coaxial cable.
19 . The signal transmission system of claim 12 , wherein the shield comprises a braided cylinder.
20 . The signal transmission system of claim 12 , wherein the shield comprises a faraday cage.
21 . A point-of-care diagnostic device, wherein the diagnostic device includes a potentiostat that includes the signal transmission system according to claim 12 , thereby providing active shielding for one or more reference electrodes in the potentiostat.
22 . A point-of-care diagnostic device having:
a potentiostat;
an analysis chamber having a reference electrode connected to the potentiostat by a first conductive trace; and
a counter electrode connected to the potentiostat by a second conductive trace, wherein part of the first conductive trace is shielded using the active shielding method of claim 1 .