Digital sensors help reduce installation, maintenance and calibration efforts

Dec. 3, 2008

Mettler Toledo has announced the launch of digital sensors with ISM (Intelligent Sensor Management) technology, which helps reduce installation, maintenance and calibration efforts — thereby improving process reliability, productivity and system availability.

Mettler Toledo's digital sensors with ISM technology are equipped with an integrated chip in the sensor head that stores all relevant sensor parameters and algorithms for enhanced sensor diagnostics. The sensor stores all relevant data to enable fast start-up when connecting it to a transmitter. When a connection is made, the sensor is automatically detected and the system parameterizes itself. When making adjustments, calibration data from the sensor is imported for adjustment purposes, and typical threshold values are set for the sensor diagnostics. The measurement signal is evaluated directly in the sensor, which then allows for a smooth transfer of all measured values from the sensor to the transmitter by means of a low-impedance signal.

The ISM technology also allows for predictive maintenance. Its goal is to perform maintenance work only as often as necessary, i.e. to calibrate, service and replace parts only when actually required. This necessitates a precise understanding of the behavior of sensors under a range of process conditions. Mettler Toledo has also developed algorithms for predictive maintenance. This means that actual process conditions — namely pH value and temperature, among other measurements — are monitored continuously, allowing for a wear matrix to be established for a particular sensor. This simplifies diagnostics in the event of measurement problems, while also providing information about the timing of the next required calibration or adjustment, and the remaining lifetime of the sensor.

Calibration values and calibration history are stored in the integrated chip in the sensor head. This allows sensors to be pre-calibrated in the controlled environment of a maintenance shop or laboratory, and then stored ready for use. This means that untrained personnel can replace sensors, while skilled lab technicians can concern themselves with using ISM diagnostic tools to determine whether and for how long the sensors can continue to be used following cleaning, conditioning and recalibration — leading to improved process efficiency and resource optimization.

Mettler Toledo's digital sensors feature the K8S connector, which has IP68 degree of protection, making it ideal for harsh, humid environments. Also, the measuring instrument used with the sensor, the M700 transmitter, allows integration of up to three modules for pH/redox, oxygen and conductivity. The system is backward- and forward-compatible, meaning that transmitters with ISM functionality can also handle conventional analog sensors. Data transfer between the sensor diagnostics and transmitter can take place over long distances via a coaxial cable, due to the low-impedance signal that is used.