High Accuracy Servo Tank Gauge

The High Accuracy Servo Tank Gauge is designed specifically for use in Custody Transfer and Inventory Management applications across the full range of modern storage tank designs. The servo tank gauge measures product level, water interface and product density profile in a single microprocessor based unit. Connecting the gauge to one of the range of MCS 3780 Series temperature probes, provides measurement of both product and vapour temperature.

Principle of Operation

The servo tank gauge measures liquid level based on the principle of liquid displacement. A displacer is suspended on a stainless steel wire payed out from a grooved drum housed in the gauge enclosure. A highly sensitive torque measurement devise continuously measures the effective weight of the displacer which, under steady state level conditions, is half immersed in the liquid. Should the level change, the displacer undergoes an apparent change of weight. The gauge microprocessor senses this change in weight and causes a servo motor to rotate the measuring drum until balance is restored.

Density is determined by measuring the effective weight of the displacer when completely immersed. Sample readings, recorded at configurable intervals as the displacer travels down through the liquid, provide density profiling.

Water interface level and tank base measurement are achieved by recording the point at which the gauge recognises the effective displacer weight in water and at the tank base respectively.

The Servo Tank Gauge Features and Key Benefits:

Intrinsically Safe (EEx ia IIB T4) with the added benefit of no electronics exposed to the tank atmosphere.

•Low Power requirements enable both power and communications to be safely distributed via one 4-wire cable running around the tank farm.

High visiblility large LCD provides selectable Level, Temperature, Interface or Density readings at all times.

•Optional display for mounting at tank base.

•Non-volatile memory that restores itself to full operation in the event of a power loss.
•Operates across a wide range of process and enviromental conditions.

•Range of installation options to suit all tanks, including high pressure applications and a flexible coupling installation for tanks with undefined deformation characteristics.

•User friendly local control by single push-button.

•Remote control and monitoring via industry standard multi-drop serial communications that includes extensive diagnostic information.

•Lightning protection through galvanic isolation.

•Extensive installation reference list in a wide variety of applications and low maintenance requirements.


•Level Accuracy: ± 1mm

•Water/Interface Accuracy: ± 2mm

•Level Measuring Range: 0-20 meters (Optional: 0-40 meters)

•Density Accuracy: ±5kg/m3

•Ripple Damping: Adjustable, typically 4 seconds

•Temperature Accuracy: ± 0.1°C (from Spot/ Multiple Averaging/ Multiple Spot Probe)
•Temperature Measuring Range: -50°C to +125°C (Optional: -200°C to Ambient or -20°C to +280°C)


•Gauge Housing: LM25-M Aluminium Alloy (Option: 316 SS)

•Measuring Drum: Anodised Aluminium (Option: 316 SS)

•Measuring Wire: AISI 316 Herdened SS (Option: Hastalloy)

•Displacer: Carbon Loaded PTFE; 90mm or 140mm diameter

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Automatic Servo Tank Gauge

The Automatic Servo Tank Gauge, with 4 mm level gauging accuracy per SIRA Report E1588583, provides continuous liquid level measurement of products stored in above- and below-ground vessels.

The servo tank gauge can be installed on atmospheric or low pressure (2.5 psig) fixed cone roof, floating roof, fixed roof with internal floating pan, or underground tanks. It can be mounted above the storage vessel or at grade.

Other versions include float check knob or float hoist, gauge head/counter for oil filling, negator motor or cartridge motor models, and stilling well and water interface models. Standard, moderate, severe, and extreme service kits are available.

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Intelligent Hybrid Servo Tank Gauge

Intelligent hybrid servo tank gauge combines the field proven high accuracy and reliability of servo gauge technology with the advantages of average density and mass measurements of the hydrostatic gauge.

Displacer weight is used to find the product level. The addition of one or two high accuracy pressure transducers to the servo tank gauge provides highly accurate product weight and level measurements, giving all the advantages, and eliminating all the shortcomings, of both Servo and HTG technologies.


  • Minimal Moving Parts (3) Ensure Reliability
  • Accuracy/Repeatability of +/- 1/32 inch (0.8mm)
  • Product and Interface, Custody Transfer
  • Handheld Infrared Calibration
  • Ground Level Display Eliminates Tank Climbing
  • Temperature, Pressure and Density
  • Product and BS&W Level Gauging in Process Industries

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