Optical sensors do not have internal electrolyte, so maintenance of this type of sensor is limited to changing the optical element. Over time, the element will lose the ability to absorb light due to a process called “bleaching”. With some sensors, this process is greatly accelerated when it is exposed to direct sunlight, and will cause irreversible damage to the sensor element.
ATI’s optical sensor element is designed to last a several years in normal operation. The sensor design allows for exposure to direct sunlight without damaging the sensor element.
GALVANIC MEMBRANED SENSOR
Membraned type D.O. sensors have been used for D.O. monitoring and control for over 40 years and have proven to be consistently accurate and reliable. Properly designed, a membraned sensor will provide continuous service for a year or more without maintenance of any kind.
Galvanic oxygen sensors function in much the same way as a battery. The sensing elements consist of platinum cathode and lead anode, with a durable Teflon membrane isolating the sensor system from the liquid being measured.
Oxygen diffuses through the membrane and is reduced to hydroxide ion on the surface of the cathode. This reaction generates current between the platinum and lead electrodes which is proportional to oxygen concentration. An RTD temperature element measures water temperature and corrects the sensor signal for its effect. The result is a D.O. measurement that’s accurate over an operating range of -5-50°C.
Choice of using either optical or galvanic membraned sensors. Electronics handle either sensor option without adjustments or special programming.
Automatic “Air Blast” sensor cleaning system available for reducing maintenance in applications where sensor fouling is a problem.
Automatic calibration check at the end of an auto-clean cycle ensures sensor is clean and responding to changing oxygen concentration.
AC or DC Power Options
Power options include universal 100-240 VAC or 12-24 VDC.
Analog Output Options
Two isolated 4-20 mA outputs are standard, with an option for a third output if required. Default setting provides analog outputs for D.O. and temperature.
Standard PID control function assignable to one analog output.
Available for either Profibus-DP, Modbus-RTU, or Ethernet-IP.
Three SPDT relays are standard, with relay functions programmable for alarm, control, or trouble indication. Three additional low power relays available as an option.
NEMA 4X (IP-66) enclosure is suitable for wall, pipe, or panel mounting.
Back-lit large LCD display provides clear visibility in any lighting conditions. A scrolling second line on the display provides additional information and programming prompts.