NMS81 Proservo Tank Gauge

NMS81 Proservo Tank Gauge

The NMS81 Proservo Tank Gauge (STG) is an intelligent tank gauge for high accuracy liquid level measurement and is suited for both custody transfer and inventory management applications employing the latest microprocessor technology.

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Designed for Industry

The NMS81 PTG is suitable for atmospheric and high pressure applications with a maximum reliability accuracy level of up to ±0.4 mm (±0.016 in). To make sure it fits your existing tank fittings, we have a wide variety of process connections to choose from.


True Multi-Measurement

In addition to level measurement, the NMS81 PTG can determine the interfaces between three liquids, specific gravity of these liquids and tank bottom. This allows the instrument to provide spot density measurements, profile the liquid density throughout the tank, or profile the stratified upper layer.


Proactive Safety Diagnostics

In the event of an abnormal measurement condition, the NMS81 PTG outputs a maximum level value to the local display and system software, thereby causing an alarm to warn your operators.


Compatible Communications

Output signals include industry standard RS-485 (MODBUS), as well as popular tank gauging protocols, such as V1 and HART. You are also able to connect a spot or average temperature probe directly to the instrument.




Industry Approval

The NMS81 PTG has FM, ATEX and IEC Ex and NEPSI approval for use in hazardous areas. It is also NMi, OIML and PTB approved for custody transfer applications and SIL2 certified for overfill prevention.


Simplifying Maintenance

Small features make your operators’ lives easier and safer; intelligent diagnostics provide advance warning of required maintenance, such as replacement of worn wire. Wetted parts are completely separated from the electronic circuit and the built in calibration window allows operators to ensure the correct position of the displacer before service work is underway.




+/-0.4 mm for (+/- 0.016 in)
(Under reference condition, according to OIML R85)



Net Weight

30kg (66.1 lb)

Enclosure Materials
  • Electrical compartment: aluminum
  • Drum chamber: 316/316L
  • Rated IP66/68, NEMA Type 4x/6P enclosure
Pressure Rating

Suitable for atmospheric and high pressure applications up to 25 bar/2.5 MPa/362 psi


Cable Entry

NPT, Metric, BSP (G) class threads

Power Requirements

High voltage type: 85 to 264 VAC, 50/ 60 Hz, 28.8 VA

Low voltage type: 52 to 75 VAC, 50/60 Hz, 21.6 VA
19 to 64 VDC, 13.4 W


Operating (Liquid) Temperature

-200 to +200°C (-328 to 392°F)

Ambient Temperature
  • Device: -40 to +60°C (-40 to +140°F)
  • Display Module: -20 to +70°C (-4 to +158°F)




Display (LCD)

Four line, white background lighting, switches to red for device errors

Language selection: English, German, Japanese



Tank side monitoring and operation can be performed by the remote display and operating module DKX001; operation via the local display is possible without opening the device

Configuration software (e.g. DeviceCare); connected via:

  • HART
  • Service port (CDI) with optional Commubox FXA291


Standard Range

28m with 316L measuring wire

Level Accuracy

+/-0.4 mm for (+/- 0.015 in)

(Under reference condition, according to OIML R85)


Interface Level

+/-2 mm (+/-0.08) (Difference of product densities 0.100 g/cm3 (6.25lb/ft3))

Spot & Profile Density

+/-0.003 g/cm³ (Under reference condition, according to OIML R85)


Medium Density

0.430 to 2.000 g/cm³ (27 to 125 lb/ft3)

Medium Density Difference

0.1 g/cm³ (6.24 lb/ft3)


0 to 5 000 mPs

For complete technical specifications, download the product manual.

Flange Type

ASME or DIN. Refer to order code for full selection.

Wire Material and Optional Ranges
  • 16 m (53.33 ft): PFA > 316L; 0.4 mm (0.016 in)
  • 22 m (73.33 ft): AlloyC276; 0.2 mm (0.008 in)
  • 28 m (93.33 ft), 36 m (120 ft), and 47 m (154.2 ft): 316L; 0.15 mm (0.006 in)
Wire Protection
  • PTFE coated Steel
  • PFTE coated Steel 316L
  • AlloyC276


Displacer Material

Stainless steel 316L, AlloyC, or PTFE

Displacer Diameter
  • 30…50mm (dependent on application)
  • Optional 70…110mm


Primary Outputs
  • Modbus RS485
  • V1
  • 4-20mA HART Ex d/XP, RTD input
  • + 4-20mA HART Ex i/IS, RTD input
Secondary I/O Analog
  • 1 x “Ex d/XP 4-20mA HART + RTD input”
  • 2 x “Ex d/XP 4-20mA HART + RTD input”
  • 1 x “Ex i/IS 4-20mA HART+ RTD input”
  • 2 x “Ex i/IS 4-20mA HART+ RTD input”
  • 1 x “Ex i/IS 4-20mA HART + RTD input”
  • 1 x “Ex d/XP 4-20mA HART + RTD input”
  • None
Secondary I/O Exd
  • 1 x “2x relay + 2x discrete I/O”
  • 2 x “2x relay + 2x discrete I/O”
  • 3 x “2x relay + 2x discrete I/O”
  • 1x “Modbus RS485”
  • 1x “Modbus RS485”, 1 x “2x relay + 2x discrete I/O”
  • 1x “Modbus RS485”, 2 x “2x relay + 2x discrete I/O”
  • None
HART Ex ia/IS Active Input

The HART Ex ia/IS active input is available by default. It needs not to be chosen explicitly when ordering a device.



Servo Gauge Comparison Guide
Easy-to-follow guide that compares the NMS80 and NMS81 servo gauges.

Parts and Accessories

Servo Tank Gauging Checklist
Checklist for Servo Tank Gauge needs.

Application Checklists

Temperature Tank Gauging Checklist
Checklist for Temperature Tank Gauging needs.


NMS81 Proservo Tank Gauge Approvals and Certificates
Please visit the Endress and Hauser website to access the approvals and certificates for the NMS81 Proservo Tank Gauge.


NMS81 Proservo Tank Gauge Installation and Operations Manual
Please visit the Endress and Hauser website to access the technical manual and operating instructions for the NMS81 Servo Tank...

Technical Specifications

NMS81 Proservo Tank Gauge Technical Specifications
The technical specifications for the NMS81 Proservo Tank Gauge.


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