Non contact radar level transmitter principle
non-contacting radar level measurement there are two main modulation techniques, pulse radar and FMCW (Frequency Modulated Continuous Wave) radar techniques. Non-contacting pulse radar sends out a microwave signal that bounces off the product surface and returns to the gauge. The transmitter measures the time delay between the transmitted and received echo signal and the on-board microprocessor calculates the distance to the liquid surface using the formula:
Distance = (Speed of light x time delay) / 2
Once the transmitter is programmed with the reference gauge height of the application – usually the bottom of the tank or chamber – the liquid level is calculated by the microprocessor.
The FMCW radar also transmits microwaves towards the product surface, but the transmitted signal is of continuously varying frequency. When the signal has travelled down to the liquid surface and back to the antenna, it is mixed with the signal that is being transmitted at that time. The difference in frequency between the received and transmitted signal is directly proportional to the distance to the liquid with high precision
Installation position of the radar Gauge
- Installation on a nozzle with diameter Less than 100mm and longer than 300 mm height.
- Avoid contact of the sensor with the wall of the tank. In case of an installation in a stilling pipe diameter less than 100mm,an in-situ calibration will be required to respect accuracy specification. For a coaxial version, there is no problem you can install it without precautions.
- Avoid an installation too close to an agitator. The cables/ rods may become entangled.
Non-contacting radar level transmitter advantages and disadvantages
Advantage of radar level Gauge :-
- Non-contacting radar provides a top-down, direct measurement as it measures the distance to the surface.
- It can be used with liquids, sludges, slurries and solid.
- No impact on accuracy if change pressure, Temperature, dielectric, conductivity and density.
- Radar devices have no moving parts so maintenance is minimal.
- No calibration required GMR required only simple configuration.
- It is a top-down, direct measurement as it measures the distance to the surface.
Disadvantage of radar Level Gauge
For non-contacting radar, good installation is the key to success. The gauge needs a clear view of the surface with a smooth, unobstructed, unrestricted mounting nozzle. Obstructions in the tank, such as pipes, strengthening bars, and agitators can cause false echoes, but most transmitters have sophisticated software algorithms to allow masking or ignoring of these echoes.
Non-contacting radar gauges can handle agitation, but their success will depend on a combination of the fluid properties and the amount of turbulence. Dielectric constant (DK) of the medium and the surface conditions will impact the measurement. The measurement may be influenced by the presence of foam. Energy tends to not be reflected by light and airy foam while a dense and heavy foam typically reflects the energy.
Radar gauge technical specification :-
|Sl. No.||Parameters||Minimum Requirements|
|1.||Instrument factory accuracy||+/ – 1 mm|
|2.||Field/ Installed Accuracy||Within +/- 4mm as per OIML|
|3.||Measuring Range||0.5 m to 30 m|
|4.||Measuring resolution||1 mm|
|5.||Product temperature range||-5 to 55 deg C|
|7.||Antenna type||Parabolic/Horn/Planar/Array/Lens as per OEM’s standards|
|8.||Antenna size||As per site condition|
|9.||Measuring principle||Frequency Modulation|
|10.||Signal processing||Digital signal processing (DSP)|
|11.||Operating frequency||X-band (9.15 to 10.85 GHz) / (70 to 80 GHz) / 6 GHz/ 10GHz/26 GHz or as per OEM’s standards|
|12.||Ambient temperature range||Refer Site Data|
|14.||Protection Class||IP 65 (NEMA 4)or better|
|15.||Relay output||SIL2 certified relay for Hi Hi level required|
|16 (a)||Hazardous Area Classification||Zone 1, Group II A & IIB, T3|
|16 (b)||Safety Approval/ Certification||Explosion proof / Intrinsic safe & PESO, SIL2 certified by|
|17.||Certification||ATEX, CENELEC, FM, BASEEFA|
|18.||Other Approvals||Department of legal metrology, custody transfer approval, OIML certificate etc|
|20.||Finishing||Chromatised /hard anodized/polyurethane paint|
|21.||Antenna material||AISI 316 (acid resistant SS) and PTFE / SS 316 and FEP or equivalent as per OEM’s standard and shall be compatible with the process fluid and weather condition.|
|22.||Process connection||On the Roof Top of the tank either on Still well pipe or Manhole cover as per site condition|
|23.||Power Supply||230 V ±10% AC 50Hz +/- 5% / 24 V DC|
|24.||Rating||Vendor to specify|
|25.||Lightning protection||Full galvanic separation|
|26.||Field communication||Vendor to specify|
|27.||Protocol||Vendor to specify|
|28.||Common mode rejection||> 150 dB|
Maximum 8 tanks shall be multi dropped in a loop connected from field to control room subject to meeting the Functional Requirement and min 25% Spare capacity of Loop
Radar Gauge Tank side Indicator
|1.||Display||Back Lit LCD /LED display|
|2.||Ambient temperature range||Refer Site Data|
|3.||Protection||IP 65 or better|
|4.||Safety||Explosion proof / Intrinsic safe|
|5.||Power Supply||Loop powered / Bus powered|
|8.||Finish||Powder coated/hard anodized/polyurethane paint/ Chrome free coated Aluminum|
|9.||Cable entry||Vendor to specify|
|10.||Parameters to be displayed||Product Level, Temperature, water interface level and alarm / other diagnostics information etc (as applicable).|
Radar Level Transmitter Manufacturer
Radar Level Transmitter Manufacturer
|Radar Type Level Transmitter Manufacturers / Vendors||Country||Website||Phone No.|
|ENDRESS & HAUSER||GERMANY||www.endress.com||+49 71562090|
|ENRAF BV||NETHERLANDS||www.enraf.com||+31 152701100|
|FUJI ELECTRIC CO LTD.||JAPAN||+81 425856201|
|KROHNE MESSTECHNIK GMBH & Co. KG||GERMANY||www.krohne.de||+49 2033010|
|SAAB TANK CONTROL (UK) LTD.||UK||www.saabtankcontrol.co.uk||+44 1189736670|
|SAKURA ENDRESS CO., LTD.||JAPAN||www.jp.endress.com||+81 422542311|