One night at 2 a.m., a telephone rang in Eckville, Alberta, Canada. Rick McKinnon checked the display on his cell phone and groaned. It was another high-level call out alarm from one of the town’s new sewage lift stations. He knew that before he drove to the pump station, the system would be running on floats instead of the new ultrasonic level controller.
Over the next several months, operators experimented to reduce the buildup of foam and grease on the water surface. Improvements were made, but none of the modifications entirely stopped the call outs.
The town changed both its ultrasonic instruments to the Greyline PSL 5.0 pump station level controller. It is designed to operate with a non-contacting ultrasonic sensor plus a signal from an alternate 4-20 mA sensor to provide redundant level signal in echo loss conditions.
An added bonus is that the embedded ultrasonic calibration is used to automatically calibrate the alternate level signal, and the two level signals are continuously compared to alarm the operator if the alternate signal is not responding to level changes.
The transition from primary to secondary level signal is seamless and transfer to the secondary signal is displayed to the operator with usage hours logged for troubleshooting or maintenance purposes.
Now if Eckville’s ultrasonic sensors lose signal from foam or grease on the water surface, the pressure sensor will take over reading instantly. As soon as the ultrasonic sensor receives new echoes, it resumes function as the primary sensor.