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Brand: KOBOLD
KOBOLD NGM Guided Wave Radar (TDR) Level Transmitter
Description
Guided wave radar level measurement that ignores density, pressure and conductivity
The KOBOLD NGM is a guided wave radar (time domain reflectometry) level transmitter for liquids and light solids. Low-energy, high-frequency pulses travel down a probe that is immersed in the product; part of the energy is reflected at the surface and the electronics calculate the level from the pulse time difference. Because the principle measures a transit time along the probe, KOBOLD states that the reading is independent of density, temperature, pressure, humidity and conductivity of the medium.
Housing, feed-through and probe form a modular system: any probe fits any housing through one universal feed-through, without special tools or welding. Measuring length reaches 20 m, temperature -150 to +250 °C and pressure -1 to +40 bar, with a HART-programmable 4 to 20 mA output and a PNP switching output.
Technical specifications
| Parameter | Specification |
|---|---|
| Measuring principle | Guided wave radar (GWR / TDR), vertical installation |
| Media | Liquids and light solids; wire rope probe NGM-4 for liquids and light solids only |
| Probe types | Single rod (6 mm), wire rope (4 mm), coaxial (17.2 mm) |
| Probe length L | Rod 100 to 3000 mm; wire rope 1000 to 20 000 mm; coaxial 100 to 6000 mm (standard), 100 to 1000 mm (high temperature) |
| Minimum dielectric constant | Rod and rope above 1.8; coaxial above 1.4 |
| Maximum viscosity | Rod and rope below 5000 cP; coaxial below 500 cP |
| Accuracy / repeatability / resolution | ±3 mm or 0.03 % of measured distance, whichever is greater / below 2 mm / below 1 mm (reference: εr 80, water, tank Ø1 m, DN 200 metal flange) |
| Process temperature | Standard -40 to +150 °C (PTFE-lined probe -15 to +100 °C); high-temperature version -200 to +250 °C with NBR O-ring or -150 to +250 °C with FKM O-ring |
| Process pressure | -1 to +40 bar (NGM-19: 0 to 4 bar) |
| Supply voltage | 12 to 30 VDC, 4-wire, reverse-polarity protected |
| Outputs | 4 to 20 mA (programmable by HART modem, total load below 500 Ω) and switching output DC PNP, NC or NO, below 200 mA |
| Wetted materials | Stainless steel 1.4401/316, 1.4404/316L or 1.4571/316Ti, PEEK; PTFE and O-ring per order code; Klinger SIL C-4400 gasket at the connection thread |
| Housing | Epoxy-coated aluminium alloy; option stainless steel 1.4401/SS316 |
| ATEX (SEV 13 ATEX 0108 X) | II 1/2G Ex ia/db IIC T6 Ga/Gb; II 1/2D Ex ia/tb IIIC T86 °C IP68 Da/Db; II 2G Ex ia db IIC T6 Gb; II 2D Ex ia tb IIIC T86 °C IP68 Db |
Choosing the probe: rod, wire rope or coaxial
The single rod probe covers the widest range of applications and is the recommended choice for installations in liquids, bypass chambers and stilling wells. Its wider detection radius needs a nozzle above 50 mm diameter, below 300 mm high, and over 100 mm clearance to walls and internals.
The wire rope probe is the one for tall tanks, limited headroom and light bulk solids, with lengths up to 20 000 mm. The coaxial probe keeps the measuring signal inside its outer tube, so tall narrow nozzles, tank walls, agitators and spray above the liquid do not disturb it, and it is the better choice for low-reflectivity liquids such as oils and hydrocarbons (dielectric constant above 1.4). It is for clean liquids only: viscous, crystallising, adhesive, fibrous or particle-laden media can build up inside the tube.
In oil-on-water interface use, a layer thinner than 70 mm is not detected and only the water level is reported.
Versions and order code
| Version | Probe | Use |
|---|---|---|
| NGM-1 | Rod probe, PEEK, no O-ring (200) or FKM with PTFE coating (900) | Standard liquids and bypass chambers |
| NGM-8 | Rod probe, high temperature, NBR (210) or FKM (220) O-ring | Hot media up to +250 °C |
| NGM-2 | Coaxial probe, EPDM (230), FKM (220) or NBR (210) | Low-reflectivity clean liquids |
| NGM-9 | Coaxial probe, high temperature, NBR (210) or FKM (220) | Hot, clean, low-dielectric liquids |
| NGM-4 | Wire rope Ø 4 mm, PEEK (200) | Tall tanks, light solids |
The datasheet order example is NGM-1200 G5 A40. Connections: G ¾ (G5), ¾” NPT (N5), EN 1092-1 flanges DN 40 to DN 100 and ASME CL150 flanges 1½” to 4″. Output A4 is 4 to 20 mA plus PNP; E4 adds the ATEX version. Options cover a stainless steel housing (E0), bypass chamber (B1 to B6, BB to BD), stilling well (S1 to SE) or bypass with roller or ball display (K0); give probe or measuring length in clear text.
Basic set-up uses a DIP switch, one push button and an LED; a spreadsheet tool with a HART modem such as HARTCOM-0 gives remote configuration and diagnostics. The switching point can sit anywhere in the measuring range.
Documents and quotation
The KOBOLD NGM datasheet (model NGM, edition 1/05-2026) is attached to this page. Browse our Level Instrumentation category for related instruments, or compare with the VEGAFLEX 81 guided wave radar.
For a quotation, send the probe type and length, connection, medium with dielectric constant and viscosity, temperature, pressure, output and any hazardous-area requirement. Confirm the inactive zones given in the datasheet at the probe top and bottom against your measuring range.
Datasheets & Documents
- Datasheet KOBOLD NGM guided wave radar level transmitter datasheet Download
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About brand
KOBOLD Messring GmbH is a German instrumentation manufacturer based in Hofheim am Taunus, founded in 1980 by Klaus J. Kobold. It develops and manufactures instruments for monitoring, measuring and regulating flow, pressure, level and temperature, and the international KOBOLD group of companies serves virtually all sectors of industry.
KOBOLD flow and level instruments
The KOBOLD range covers Coriolis, thermal mass, magnetic inductive, turbine, oval gear, oscillation and variable area flow meters and flow switches, together with guided wave radar, 80 GHz radar, magnetostrictive, tuning fork and bypass level instruments. Many models carry ATEX or IECEx approvals, and several offer HART, Modbus or IO-Link communication.
Requesting KOBOLD instruments from Seven Star LLC
Seven Star LLC, an independent supplier in Muscat, lists selected KOBOLD flow and level instruments for oil and gas, water, power and process plants in Oman and the GCC. Send the model code, measuring range, process connection and approvals needed, and Seven Star LLC will prepare a quotation from the KOBOLD datasheet.
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Frequently Asked Questions
What is the maximum measuring length of the KOBOLD NGM?
Up to 20 m with the wire rope probe; the single rod probe is available up to 3000 mm and the coaxial probe up to 6000 mm.
Which process conditions does the NGM cover?
Medium temperature from -150 to +250 °C in the high-temperature versions and pressure from -1 to +40 bar, except the NGM-19 version, which is 0 to 4 bar.
Is the NGM affected by density or conductivity?
No. KOBOLD states that the guided wave radar reading is independent of density, temperature, pressure, humidity and conductivity.
What outputs does the NGM provide?
A 4 to 20 mA output programmable by HART modem and a PNP switching output with a 4-wire 12 to 30 VDC supply.
Does the NGM have a hazardous-area approval?
The datasheet lists ATEX certificate SEV 13 ATEX 0108 X with Ex ia and Ex db marking; order the ATEX output code E4 and check the marking against your zone.
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