About SCR Systems

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International standards call for highly effective exhaust after-treatment systems in order to mitigate the environmental impact of diesel engine emissions globally. The Selective Catalytic Reduction (SCR) system is one of the exhaust after-treatment systems adopted by vehicle and engine manufacturers to reduce emissions pollutants such as NOx (generic term for NO, nitric oxide, and NO2, nitrogen dioxide) from the engine exhaust gas.

Diesel Exhaust Fluid (DEF), or AdBlue, is a 32.5% urea, or aqueous ammonia solution, that is injected into the SCR system to convert NOx into harmless H2O and N2.

Since 2003, KUS has been working with global exhaust after-treatment system integrators, vehicle and engine OEMs to design and manufacture components for the SCR system in accordance with ISO 22241 standards in order to meet emission laws and regulations.

DEF Level Sensors

As one of the most capable designer and manufacturers of the DEF Level Sending Unit, KUS understands the importance of the level sending unit’s reliability, accuracy, and durability.

The DEF Level Sending unit integrates liquid level and temperature measurement functions, as well as a heating function utilizing the engine’s coolant. There is also an option to specify a urea quality sensor, which measures the quality, or concentration level of the urea solution, so as to ensure proper operation of the SCR system.

When selecting the most appropriate DEF Level Sending Unit for your application, there are two design functions that should be considered: the way the DEF Level Sending Unit mounts to the tank, and the coolant heading tube body form factor.

DEF Level Sender with Quality Sensor - CS8MT

Mounting Head Options

Bayonet Mount

The Bayonet Mounting heads are the standard mounting method for DEF/AdBlue level senders. The level sender is mounted on to the tank through a matching bayonet opening, twisted in place and sealed with an o-ring.

Rubber Head Mount

The Rubber Head Mounting was originally developed for narrow tanks that have small installation areas, but have become a very popular choice for OEMs due to its ease of installation and sealing factor.

Flange and Bolt Mount

The level sender is mounted by its flange to the tank using bolt or screws. No need for specialized installation tool make this an easy mounting choice for vehicle OEMs, tank manufactures, and aftertreatment system integrators.

Heating Tube Body Forms


O-shaped DEF Level Sender is the standard option for most applications. Engine coolant is circulated through the heating tubes, thawing the frozen DEF, thus ensuring the proper function of the SCR system within required time-frame.

O-Shaped Heating


L-shape DEF Level Sender was developed for use with large DEF tanks. The L shaped tube increases the heating area of the level sender so that adequate amounts can be thawed within the required time to ensure proper operation of the SCR system.



The Spiral, or S-shaped DEF Level Sender is recommended for use in extreme-cold climates. The spiral form factor increases the heating efficiency of the level sender, allowing the SCR system to function according to specifications.


No Heating

In regions where the climate does not get cold enough for the DEF to freeze, there is no need for heating coils. KUS offers DEF level senders with only level detection, DEF suction and return. This provides a cost-effective solution for DEF level senders without the added costs of the heating tubes.

No Heating Tube
80L AdBlue Tank (21 Gallons)

DEF Tank and Custom Tank Assembly Solutions

KUS is in the unique position of being the only manufacturer of both the DEF Tank and DEF Level Senders currently on the market. This means we are able to engineer, design and validate DEF Tanks and Level Senders concurrently.

KUS’s engineering and design team have more than 10 years of experience designing custom DEF Tank and Total Tank Assemblies for SCR system integrators, vehicle OEMs, and engine OEMs across the USA, Europe, Russia, India, and China.

The Total Tank Assemblies are engineered and designed for the SCR systems according to ISO 22241 standards.

  • The DEF Tank is constructed out of high-density polyethylene (HDPE) through a blow molding process.
  • The DEF Level Sender measures the temperature and fluid level in the tank.
  • There is an option to specify in a quality sensor which measures the quality, or concentration level of the urea solution, so to ensure proper operation of the SCR system.

In addition to custom solutions, KUS is now offering standard ready-to-market DEF Total Tank Assemblies ranging from 16L to 80L.

DEF Tank Assembly Customization Options

You can customize DEF tanks to get the most out of your equipment. By using a custom DEF tank, your engineering team will have greater flexibility when designing products. There are several ways to customize DEF tanks. These options include:

  • Creating DEF tanks in the exact dimensions your team requires. 
  • Stress-testing the DEF tank to your specifications. 
  • Building specialized signal systems. These can be analog or digital systems, for easier readings at a glance. 
  • Aesthetic changes. These changes can include custom colors, fonts, materials, backlights, or wire colorings. These changes can increase brand awareness.

DEF Quality Sensor

DEF Level Senders equiped with Urea Quality Sensor were developed for the increasing stringent emissions laws and regulations.

The urea quality sensor is used to accurately monitor the concentration and quality of the DEF solution, and alert the user if the solution deviates from the acceptable concentration range or if there are any contaminants in the DEF tank. DEF’s concentration is extremely important in enabling the SCR system to be able to perform effectively and accurately according to its specification.

KUS takes a modular approach by offering 3 type of Urea Quality Sensor. Our engineers will work with the customer in selecting the Urea Quality Sensor that best fit your application.

Optical (OQS)

Different concentration of DEF will have different refractive indices. By sending a beam of light through DEF and capturing where it lands on the CMOS, the OQS will be able to calculating the angle of refraction of light through the DEF and be able to determine the concentration of the DEF.

Optical Quality Sensor
Optical Quality Sensor

Heat Capacitance (SQS)

Different concentration of DEF will transfer heat at different rates. SQS measures the rate at which it takes to heat up a small amount of DEF in a chamber to determine its thermal coefficient, and therefore calculate the concentration of the DEF.

Heat Capacitance Quality Sensor
Heat Capacitance Quality Sensor

Ultrasonic (TQS)

Ultrasonic wave will travel and propagate through different medium and concentration of liquid at different speed. By using a fixed distance, and calculate the time it takes for the ultrasound wave to make a round-trip in the DEF, we can determine the concentration of the DEF solution.

Ultrasonic Quality Sensor
Ultrasonic Quality Sensor