If you cannot zero balance a pressure catheter, fluid may have got inside the catheter, or the pressure sensor diaphragm may be cracked or broken. One way to check the functionality of the pressure sensor is to connect an Ohmmeter (resistance gauge) across the pins of the pressure sensor connector. The bridge on the sensor should have symmetrical input and output impedances of approximately 1,000 ohms.
There are four gold pins located on the back end of the connector. Using the ohmmeter, check the resistance between the outer two pins on the connector as well as the inner two pins. The resistance measurement should read approximately 1,000 ohms. If either reading is dramatically different than 1,000 ohms, chances are the pressure sensor is broken.
If you suspect fluid has got inside the catheter, or the pressure sensor diaphragm is cracked or broken, contact ADInstruments Support for information on how to send the catheter back for evaluation and possible repair. If you measured the resistance between the connector pins, please report those readings to ADInstruments.