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8900d High Accuracy Radar Tank Gauge

The Motherwell Control Systems Limited 8900d High Accuracy Radar Tank Gauge is a non-intrusive FMCW (Frequency Modulated Continuous Wave) radar tank gauge which uses a combination of the latest digital technology and unique signal processing to provide level measurement accurate to ±1mm. The unit optionally provides temperature (averaging / spot), average density, water interface measurement and hardware and software alarms.


Designed for use in Custody Transfer and inventory management Applications including problematic petrochemicals and products stored at temperature and pressure extremes.

Product Description:

The 8900d is the latest generation of level gauges manufactured by Motherwell Control Systems and is a non-contact high accuracy tank gauge with no moving parts working on the principle of radar.

The construction of the 8900d is very modular in nature allowing for a wide range of options such as different flange sizes and adapters to suit a wide range of process connections.

Digital technology and unique signal processing are used and means that there is no reference coil as is the case with analogue radar gauges and the gauge is thus not susceptible to temperature and pressure extremes.

The electronics within the gauge are modular in nature, based on a card frame system complete with watchdog feature, which warns of any part of the system needing attention.

The 8900d is a complete tank gauging system located at the top of the tank and readily accepts signals from additional tank sensors to provide temperature, pressure and water interface information. For example, connecting the 8900d to the MCS 3791 series temperature probes provides measurement of both product and vapour temperature together with water interface measurement.

8900d Level Measurement

  • Dynamic product level measurement – accurate to ±1mm.
  • Self referencing through tank mapping software
  • Up to four level alarm contacts

8900d Temperature Measurement

  • Temperature measurement accurate to *0.1 degrees C
  • Accepts Single Spot, Multiple Spot or averaging Temperature Probes
  • All elements of Multiple and Averaging Probes are read continuously
  • Temperature profiling illustrates thermal product stratification and provides vapour temperature measurement.

Principle of Operation:

Liquid level measurement is achieved by measuring the time of flight for a radio wave to travel from the radar gauge to the liquid surface and back again.

The 8900d Radar Gauge uses the frequency modulated continuous wave (FMCW) microwave radar principle, operating at an average frequency of approx. 10 GHz.

A high stability radio frequency is generated within the gauge, whose frequency is linearly ramped between 9.5 and 10.5 GHz, which is then fed to a dieletric rod antenna from which it is launched into free space.

In normal operation the gauge is mounted at the top of the storage tank with its antenna pointing down towards the surface of the product inside.

The radio wave signal is emitted from the rod antenna and radiates outwards ‘seeing’ all the tank internals. The reflected radio wave is then collected by the same antenna and the gauge compares the difference in frequency between the outward and return radio waves.

The frequency difference is proportional to the distance travelled.

The resulting frequency difference then undergoes a number of processes including Fourier Transform techniques and peak location algorithms which are then used to digitally locate the peak frequency corresponding to the product level reflection from which the liquid level is then calculated and displayed on a liquid crystal display inside the unit.


Key Benefits:

  • Maintenance Free – There are no moving parts within the gauge and thus no problems associated with mechanical wear and tear.

  • Non-Contact Technology – suitable for difficult products such as bitumens or waxes.

  • Low Power Requirements – Both power and communications can be safely distributed via one 4-wire cable running around the tank farm in multidrop format.

  • Range of Installation Options – wide range of installation options on most types of storage tank design including that storing product at temperature and pressure extremes. The radar works in both stilling pipes and free tank space and can be installed in conjunction with high pressure isolating valves dependent on valve size.

  • Modular Design – Both the gauge body and internals are modular in nature resulting in greater flexibility to suit a wide range of process connections and different antenna as required.

  • PTFE Rod Antenna – the standard narrow rod antenna produces a broad beam and is easy to install with further advantages including:

    • Installation either inside or outside of the tank (longer adaptor required).

    • Ease of Installation, as the antenna is not directionally sensitive.

    • PTFE surface resists surface coating build up and offers a degree of self cleaning – liquid runs off.


  • Lightning Protection – through galvanic and optical isolation.

Inventory Management System

The 8900d High Accuracy Radar Tank Gauge is fully compatible with the full range of MCS Tank Gauging Systems, including MCS Series 5000 Inventory Management System.