Sensors

Virtually all substances can be measured by an ultrasonic sensor. One of the attractive aspects of this technology is that the ultrasonic sensor never comes in direct contact with the monitored material. Oftentimes, they are the most inexpensive option for monitoring highly corrosive liquids.

When to use it:

There are a couple of circumstances that would lead one to consider an ultrasonic sensor.

1. The monitored liquid is highly corrosive.
2. The liquid is moving or flowing.
3. The monitored substance settles to a nearly flat surface.

How it works:

An ultrasonic sensor system consists of essentially one basic component: the sensor head. Ultrasonic works on the basic principle that the longer an echo takes to return to the listener, the farther away the object that bounced the echo back. An ultrasonic sensor is mounted at the top of a tank and generates an inaudible, high frequency pulse that is aimed toward the bottom of the tank. The sound strikes the surface of the monitored substance and returns back to the sensor. The time it takes for the sound to leave and return back is calculated. Because the speed of sound is known, the travel time is converted into distance traveled. Once the distance traveled is known, it is short work to determine the fullness or emptiness of a storage tank.

Virtually all liquids can be measured using one of the two most common sensor technologies: differential pressure and ultrasonic. Of the two, by far the most common in use today is differential pressure. One of the attractive aspects of this technology is that the differential pressure sensor head can be constructed of various materials suitable for submersion in virtually all non-corrosive liquids. Oftentimes, they are the most inexpensive option for monitoring bulk liquids.

When to use it:

There are a couple of circumstances that would lead one to consider differential pressure.

1. The monitored liquid isn’t highly corrosive. TankLink’s differential pressure sensors are available for measuring most liquids from pure water through mildly corrosive liquids.
2. Either the area or the liquid requires intrinsic safety certification.
3. The liquid isn’t moving or flowing. The differential pressure sensor is essentially a cable with a weight (sensor head) on the end of it.

Flowing water would move the sensor and it could be either pushed up by the current giving a false reading or it could be pushed into discharge piping.

How it works:

A differential pressure sensor system consists of a couple of basic components. First is the sensor head containing a diaphragm and the electronics to monitor it. Second is a cable that connects to the telemetry head unit which contains the power and data cable as well as a air snorkel to the outer environment. All components are designed to come in direct contact with the monitored liquid. These parts are called the "wetted" parts.

The electronics in the sensor head detect the deflection in the diaphragm and translate this into a voltage level. The snorkel running through the cable provides the sensor the "difference" needed to calculate the differential pressure—regular air from the snorkel on one side of the sensor and the liquids pressure deflecting the diaphragm on the other. As the liquid level lowers, the differential pressure on the diaphragm lowers and thus the communicated voltage lowers. All sensors provided by TankLink are calibrated at our factory using equipment dedicated to that purpose.

Common options:

Coatings: The coatings on the differential pressure cable are carefully selected for liquid compatibility. Numerous coatings are available that not only protect the system from the liquid, but also extend the environmental operating range for the overall system.

PSI Ranges: TankLink offers various PSI ranges for our differential pressure sensors. The various options are necessary to accommodate the different shapes and sizes of liquid storage tanks. The more liquid in the tank the higher the PSI range required. This isn’t because the sensor would malfunction, but because the operating range of the voltage send to the telemetry unit is best used when the PSI range is closely matched to the expected weight of the monitored liquid.

Cable lengths: TankLink will customize the cable length for customers if we don’t already have a suitable cable length in stock. Custom cable lengths are fully potted with protective epoxies and maintain their hermetic seal.