Errors caused by shorting the electrode cables

Often, Instrumentation technicians like to shorten cables to match the installation. This is strongly discouraged with Analytical Sensors. Yokogawa has designed cables with a special layer of conductive plastic to ensure maximum noise immunity. This layer can be very difficult to remove. If done improperly the shortened cables will often give intermittent problems. They may show noisy signals, signals that jump when the cables are touched or moved, or may not work at all. This is often difficult to diagnose and may lead to customers replacing the entire system because they lose confidence in the integrity of the analyzer. For this reason we recommend that the cables be left at their original length. Any unused cable can be coiled up and immobilized using Plastic Wire-ties or tape to keep it out of the way and prevent wind or weather from causing it to move.

Keep in mind that pH analyzers are measuring a voltage signal through the glass of the pH sensor. This sensor may have over 1,000 MegOhms of resistance. In these conditions the cables must be perfect to keep the voltage signal from leaking away before it reaches the Transmitter. Even the oil from your fingers in the wrong place can short out this signal and cause errors.