80G Radar Level Measurement for Grain Silos

Case Study: 80G Radar Level Measurement in a Grain Silo — Maize and Wheat Application: Grain Storage (Maize / Wheat) | Product: Silver Instruments SDRD87 80G Radar Level Meter | Range: 18.2 m

Quick Answer

A grain storage facility measuring maize and wheat in a 20.4 m silo selected the Silver Instruments SDRD87 80G FMCW radar level meters. Measuring range 18.2 m, 40°C operating temperature, 70% humidity, and granular material at 500–3,000 μm particle size, 720 kg /m³ bulk density. DN100 PN16 SS316L flange, PTFE antenna, 4-20 mA / HART 2-wire output, Ex d ia T2~T6 Gb ATEX approval. Non-contact measurement eliminates sensor wear on abrasive grain surfaces.

1. Application Background

80G Radar level meter for Grain Silo Level Measurement

A grain storage operator submitted an enquiry form for a silo level measurement requirement. The silo stores maize and wheat in alternating cycles. Total silo height K is 20.4 m. The extension pipe above the roof is 2.1 m (B). That puts the actual measuring span H at 18.2 m from the flange face down to the silo floor.

The customer marked granular material, particle size 500 to 3,000 μm, bulk density 720 kg/m³. Tank temperature reaches 40°C. Humidity inside the silo is 70% — which rules out ultrasonic level meters immediately. Ultrasonic attenuation in high-humidity, dust-laden air is significant, and ultrasonic units frequently lose echo on dry grain surfaces with low acoustic reflectivity.

Power supply is AC 220 V. The customer requested a flange connection ("as per availability") and no RCU controller or separate control box. One instrument, one cable, straight to the PLC.

The SDRD87 80G radar level meter was selected. Here is why, and how it was configured.

2. Why 80G Radar for Grain

Grain silos present three problems for level measurement: dust during filling, an uneven and shifting surface, and moderate dielectric constant (typically εr 2 to 4 for dry grain).

Ultrasonic sensors struggle with both the dust and the low sound reflectivity of grain. Guided wave radar works but requires a probe running the full depth of the silo — on an 18 m silo that is a long, exposed probe subject to mechanical damage during grain loading.

80G Radar level meter with Gimbal flange for solids

Non-contact 80G radar avoids both problems. The 80 GHz frequency produces a 4° beam angle — tight enough to avoid false echoes from silo walls at 18 m depth. The FMCW signal penetrates grain dust without attenuation. And the ±5 mm accuracy is more than sufficient for inventory management in a grain store.

In practice, the sensor mounts on the silo roof, points straight down, and never touches the grain. There is no mechanical wear. No calibration drift from abrasion. The PTFE antenna surface is grain-safe and easy to clean if dust accumulates.

3. Installation Configuration

The SDRD87 is mounted at the top of the extension pipe (B = 2.1 m). This keeps the antenna 2.1 m above the roof, allowing space for maintenance access and keeping it clear of any roof condensation.

The gimbal (NW antenna option) allows fine angle adjustment after installation. On a grain silo where the fill point may be off-centre, being able to tilt the beam 5 to 10° toward the main grain mass helps establish a stable echo. We have seen this on customer sites where centre-fill creates a conical pile — the gimbal lets the technician aim at the slope rather than the peak.

Process connection is DN100 PN16 flange in SS316L. The flange matches the roof nozzle the customer had available. FKM sealing handles the 40°C process temperature with margin to spare. Output is 4-20 mA / HART 2-wire, loop-powered from a 24V DC supply derived from the site’s AC 220 V panel. The M20x1.5 cable entry matches standard industrial conduit practice in most markets.

The unit carries Ex d ia T2~T6 Gb approval (intrinsic safety plus explosion-proof). Grain dust is combustible. ATEX / IECEx Zone 1 certification is not always a mandatory requirement for grain silos, but having it means the same instrument model covers both standard and classified installations without a product change.

4. Instrument Specification

Parameter	Value
Model	SDRD87-G-NW-A-FC-A-B-A-M-A
Measuring principle	80G FMCW (Frequency Modulated Continuous Wave)
Beam angle (3dB)	4°
Measurement range	18.2 m (silo K = 20.4 m, extension pipe B = 2.1 m)
Accuracy	±5 mm
Operating temperature	-40 to 130°C (NW antenna)
Operating pressure	Normal pressure (non-pressurised silo)
Process connection	DN100 PN16 Flange, SS316L
Antenna material	PTFE (-40 to 200°C)
Sealing	FKM (-40 to 200°C)
Output signal	4-20 mA / HART, 2-wire
Power supply	24V DC (loop-powered)
Housing	Aluminium / IP67
Cable entry	M20 x 1.5
Display	Integral LCD
Approvals	Ex d ia T2~T6 Gb (intrinsic safety + explosion-proof)
Medium	Maize / Wheat (granular, 500–3,000 μm, 720 kg/m³)
Power supply voltage	AC 220 V (converted to 24V DC at panel)

5. Key Selection Points for Grain Silo Level Measurement

Grain Silo Level Measurement

Non-contact measurement: no probe contact with abrasive grain, no mechanical wear, no contamination risk.
80G frequency: 4° beam angle avoids silo wall echoes at 18 m depth. 26G units with 8–8° beam angles can produce false echoes in silos under 4 m diameter at this depth.
Humidity insensitivity: 70% relative humidity inside the silo has no effect on microwave signal propagation.
Dust insensitivity: grain filling generates significant dust. 80G radar signal is unaffected.
PTFE antenna: inert to grain oils and surface residues. Mechanically robust for top-of-silo service.
Gimbal mount (NW option): angle adjustment to optimise echo from irregular grain surface.
Ex d ia T2~T6 Gb approval: covers grain dust combustibility classification where required.

6. Get a Quote for Your Silo

If you have a grain, feed, or bulk solid silo application, send us these parameters and we will confirm the model and quote within 24 hours:

Silo total height K (m) and extension pipe height B (m)
Material name and form (powder / granular / lump)
Particle size (μm) and bulk density (kg/m³)
Operating temperature (°C) and humidity (%)
Process connection available (flange size / thread)
Hazardous area classification (if applicable)
Required output: 4-20 mA, HART, or RS485

Contact Silver Automation Instruments: inquiry@silverinstruments.com | WhatsApp +86-18936759191 | SDRD87 product page

FAQ

Can 80G radar measure dry grain reliably?

Yes. Dry grain has a dielectric constant of roughly εr 2 to 3. 80G FMCW radar can detect surfaces down to εr 1.5. The tight 4° beam angle of the SDRD87 concentrates the signal on the grain surface rather than scattering onto silo walls. In practice, stable echo is achievable in most grain silo geometries down to low fill levels.

Why not use ultrasonic level measurement for grain?

High humidity (70% in this case) significantly attenuates ultrasonic signals in the air column above grain. Grain dust during filling causes further signal loss. Ultrasonic units also have a minimum dead zone of 20 to 50 cm from the sensor face, and at 18 m range the temperature compensation errors become meaningful. Radar is more reliable for this application.

What is the minimum detectable level (blind zone) for the SDRD87?

The SDRD87 has a blind zone of approximately 0.1 to 0.3 m from the antenna face. In this installation, the extension pipe places the antenna 2.1 m above the silo roof, so the effective bottom of measurement is very close to the silo floor. There is no concern about blind zone interfering with usable measurement range in this 18.2 m application.

Is ATEX certification required for a grain silo?

Grain dust is combustible and can create explosive atmospheres during active filling or emptying. Whether formal ATEX Zone classification is applied depends on local regulations and the site hazardous area assessment. The SDRD87 carries Ex d ia T2~T6 Gb approval as standard, so it meets the requirement if the silo is classified. If not, the same unit still applies — the approval costs nothing extra in this configuration.

Does Silver Instruments supply radar level meters for other bulk solids?

Yes. The SDRD87 series covers cement, coal, fly ash, limestone powder, plastic pellets, fertiliser granules, and similar bulk solid applications. The key input parameters are material dielectric constant, particle size, bulk density, and silo geometry. Send us the datasheet or fill in the basic information form and we will confirm suitability.

80G Radar Level Measurement in Grain Silos