The RTC 3960 gauge measures the level in Liquefied Petroleum Gas (LPG) or Liquefied Natural Gas (LNG) tanks using a 4-inch still-pipe as a waveguide. It gives high reliability with no moving parts and no contact with the liquid. All electronics are housed in the explosion-proof housing, located outside the tank. Reference devices make it possible to verify measurements without opening the tank - no need for expensive calibration chambers and large-size valves.

The still-pipe ensures a sufficiently strong echo even under surface boiling and turbulent conditions.

The gauge uses state-of-the-art Frequency Modulated Continuous Wave (FMCW) radar technology. For highest measuring accuracy the gauge can be equipped with a pressure sensor for calculation of vapor content.

High Versatility
The 3960 has inputs for temperature sensors, HART® based pressure sensors and other analog inputs as well as analog and relay outputs. All data is transmitted on the two-wire TRL/2 field bus. As an option the gauge can be equipped with other output buses such as Foundation™ fieldbus Profibus DP or Tiway. It can also emulate other vendor's buses when installed in existing tank gauging systems.

Designed for high pressure use
The pressure seal is a quarts window approved for use in pressure vessels up to 25 bars (365 psig). The gauge has an optional fire proof block valve and a vapor pressure sensor.
Unit of Measure


Measuring Principle

N/A FMCW radar with digital reference and temperature control.

Antenna Type

N/A High precision cone.

Instrument Accuracy

N/A ± 0.5 mm± 5/256 in

Measuring Range

N/A 0.5 to 60 m (1.6 to 200 ft), For longer measuring range, please consult your Rosemount Tank Gauging representative

Ambient Temperature

N/A -40 to +70 ºC-40 to +158 ºF

Operating Temperature at Ball Valve

N/A -55 to 90 ºC-67 to 194 ºF

Operating Temperature in Tank

N/A -170 to 90 ºC-274 to 194 ºF

Max. Pressure

N/A up to 25 barup to 365 psig

Material Exposed to Tank Atmosphere

N/A Acid proof steel EN 1.4436 (AISI316) and quartz.

Supply Voltage

N/A 100-240 VAC, 50-60 Hz. Optional 20-28 VDC (max. 30 W) Optional 34-70 VAC Optional 48-99 VDC


N/A Inputs: Temperature (Pt 100), 2 pcs 4-20 mA (of which one HART® Master). Outputs: TRL/2 field bus, 1 pc 4-20 mA, Profibus DP, Foundation Fieldbus™, Tiway, 2 pcs relays, other vendor's field buses.


N/A On separate DAU, RDU or remotely in control room.

Still-Pipe Dimensions and Flange

N/A 4-in (Sch 10 or Sch 40) or 100 mm inner diameter stainless steel. 6-in flange.


N/A Aluminum, designed for IP 66 & 67.


N/A 38 kg (84 lb) for 6-in. 150 psi 48 kg (106 lb) for 6-in. 300 psi

Hazardous Locations Certifications

N/A ATEX: C€ 0575 II 1/2 G EEx d[ia] IIBT6 IECEx: Ex d IIB T6 UL: Class I, Div I, Groups C and D

Product Type

N/A LPG Gauge RTG 3960


N/A Rosemount Tank Gauging


N/A Technical details are subject to change without prior notice. For more technical details see the Rex Technical Description.


N/A Benefits

  • Highest reliability
  • Verification of measurement with closed tank. Non-contact measurement
  • Still-pipe installation of antenna ensuring strong echo even under surface boiling and turbulent conditions.
  • Custody transfer accuracy
  • SIL 2 Safety Functions
  • TUV Overfill Protection
  • Integrated in TankRadar Rex inventory tank gauging system.
  • Emulates other vendor's field buses


N/A The gauge consists of two main parts; the exchangeable transmitter head housing all electronics (installed on top of the tank) and the antenna which is the only part in contact with tank atmosphere.
The gauge fits to a 6-inch flange and requires installation of a customer supplied still-pipe. In order to verify measurements in the pressurized tank, a reference pin is installed in a still-pipe hole at the top, and a deflection plate with reflection ring is installed at the bottom. Existing cabling is used for data transmission.

Safety Functions

N/A TankRadar Rex can replace a traditional Hi-Hi alarm device. With the RTC 3950 it is possible to use the gauge for overfill protection and simultaneously use it for high accuracy level measurement.

The Rosemount TankRadar Rex (RTG 3900 Series) has been assessed by third party and considered suitable for use in SIL 2 safety functions according to IEC 61508/61511. The decision on the usage of proven-in-use devices, however, is always with the end-user. The safety function is based on the relay outputs, by using either one or a combination of two, for overfill or dry run protection. TankRadar Rex is approved as an overfill protection device by TON/ (Technische Uberwachungsverein) (TUV is a German testing authority responsible for testing overfill protection equipment according to the requirements stated in the German Federal Water Act (WHG) concerning water protection.)