Grain Moisture Meters
Accurate grain moisture measurement is the single most important variable at harvest, at delivery and in storage. Ecotao supplies professional-grade grain moisture meters — from entry-level field testers to Draminski's flagship instruments — to South African farmers, co-ops, grain traders, millers and coffee processors.
What is a grain moisture meter?
A grain moisture meter is a handheld instrument that measures the percentage of water in a grain sample — quickly, non-destructively and without laboratory equipment. Professional models use the impedance measurement method: a small electrical signal is passed through the grain sample at one or more frequencies. Because water conducts electricity far better than dry starch or protein, the instrument converts the measured electrical resistance into a moisture percentage, displaying the result in seconds.
Modern instruments like the Draminski GMM Mini and TwistGrain Pro use 4-frequency impedance measurement — a technique that dramatically improves stability across varying grain temperatures, ensuring readings remain accurate whether measured at 8 °C in a cold silo or 35 °C during Highveld summer harvest. Automatic temperature compensation is built into all Draminski models, so you do not need to apply manual correction factors in the field.
Our Range
Grain moisture meters available from Ecotao
All products can be ordered via the Ecotao Store or by contacting us directly. No prices are displayed on this information page — visit the store for current pricing.
Smart Sensor AR991 Digital Grain Moisture Meter
SKU: AR991 | Brand: Smart Sensor
A reliable and affordable handheld grain moisture meter for field and storage use. The AR991 features a 250 mm insertion probe, backlit LCD display, voice-over readout, and built-in memory for saving readings. Ideal for smaller farming operations, co-ops and traders who need a fast, straightforward moisture check across 14 common grain and oilseed types without PC connectivity requirements.
- Measurement methodResistive probe (insertion)
- Grain types14 (incl. wheat, maize, barley, rice, sorghum, soybean, paddy, rapeseed)
- Resolution0.1%
- Probe length250 mm
- DisplayBacklit LCD
- Power4 × 1.5 V AA batteries
- Data loggingLast reading + settings retained
- Special featuresVoice-over readout, auto power-off, battery indicator
- AvailabilityIn stock
Draminski GMM Mini Professional Grain Moisture Meter
SKU: GMM-Mini | Brand: Draminski
A compact, professional-grade instrument designed for South African field and silo conditions. The GMM Mini uses a 270 ml dosing chamber with a purpose-built dispenser and slide to ensure a repeatable, correctly-sized grain sample every time — eliminating the guesswork that causes reading variation. With 34 grain types selectable (including a dedicated maize grits/groat setting for the snack food industry) and automatic temperature compensation, it is the preferred field instrument for grain buyers, silo managers and agronomists.
- Measurement methodImpedance (chamber)
- Grain types34 (incl. maize grits, canola, sunflower, sorghum, millet)
- Moisture rangeUp to 43% (grain type dependent)
- Resolution0.1% moisture / 0.1 °C temperature
- Accuracy±1% to ±1.5% depending on moisture level
- Sample volume270 ml
- DisplayBacklit graphic LCD (grain type, % moisture, temp)
- Power2 × AA Alkaline — approx. 151 hours (no backlight)
- Size190 × 125 × 80 mm, 700 g
- IncludesDispenser, slide, batteries, manual
- AvailabilityGenerally in stock
Draminski TwistGrain Pro Grain Moisture Meter
SKU: TG-Pro | Brand: Draminski
The TwistGrain Pro is Draminski's premier portable moisture meter and the instrument of choice for commercial grain operations, grain co-ops, export traders and research stations. Its unique twist-and-compress cap mechanism with built-in buzzer alerts the user when grain compression in the 90 ml chamber is sufficient — eliminating the most common source of user-dependent measurement error. 4-frequency impedance measurement and a built-in stainless-steel chamber ensure long-term stability and corrosion resistance. Free multi-language PC software generates Excel reports, moisture-over-time graphs, and PDF summaries from 50 000 stored readings.
- Measurement method4-frequency impedance
- Grain types42 standard (expandable to 400 via software)
- Moisture rangeUp to 40% (grain type dependent)
- Resolution0.1% moisture / 0.1 °C temperature
- Accuracy±0.5% for standardised grains
- Sample volume90 ml
- DisplayBacklit graphic LCD 2"
- Memory50 000 readings with date & time
- PC connectivityUSB — free Excel / PDF software
- Power4 × AA + 1 × CR-2032 — approx. 77 hours
- Size165 × 70 × 75 mm, 550 g
- IncludesCarry case, strap, USB cable, batteries, manual
- AvailabilityGenerally in stock; 4–6 weeks if not
Draminski TG-Pro-Coffee Twist Grain Pro Coffee & Cocoa Moisture Meter
SKU: TG-Pro Coffee | Brand: Draminski
The TG-Pro-Coffee is built on the proven TwistGrain Pro platform but calibrated exclusively for the specialty coffee and cocoa supply chain. It covers every stage of the coffee process — from green and parchment beans through to roasted and ground coffee — as well as cocoa beans, making it indispensable for South African coffee importers, roasters, quality controllers and exporters. The screw-cap mechanism with buzzer alert ensures consistent compression across small 90 ml samples. Offset calibration allows the user to align readings against their own reference samples without factory service.
- Measurement method4-frequency impedance
- Species (coffee & cocoa)11 calibrations
- Moisture rangeUp to 40% (species dependent)
- Resolution0.1% moisture / 1 °C temperature
- Accuracy±0.5% for standardised species
- Sample volume90 ml
- Memory50 000 readings with date & time
- PC connectivityUSB — free software included
- Power4 × AA — approx. 77 hours (no backlight)
- Size165 × 70 × 75 mm, 550 g
- IncludesCarry case, strap, USB cable, batteries, manual
- AvailabilityIn stock
Side-by-Side Comparison
Grain moisture meter comparison
Use this table to compare all four instruments across the key decision criteria before purchasing.
← Scroll to see full table →
| Feature | AR991 Smart Sensor |
GMM Mini Draminski |
TwistGrain Pro Draminski |
TG-Pro-Coffee Draminski |
|---|---|---|---|---|
| Measurement method | Resistive probe | Impedance (chamber) | 4-frequency impedance | 4-frequency impedance |
| Sample method | Probe insertion into bulk grain | 270 ml chamber with dosing dispenser | 90 ml twist-cap chamber | 90 ml twist-cap chamber |
| Grain / species types | 14 | 34 | 42 (up to 400 via software) | 11 coffee & cocoa species |
| Max moisture range | Varies by crop (up to ~55% for paddy) | Up to 43% | Up to 40% | Up to 40% |
| Resolution | 0.1% | 0.1% / 0.1 °C | 0.1% / 0.1 °C | 0.1% / 1 °C |
| Accuracy | Not specified | ±1% to ±1.5% | ±0.5% (normalised grains) | ±0.5% (normalised species) |
| Temperature compensation | ✔ Automatic | ✔ Automatic | ✔ Automatic | ✔ Automatic |
| Backlit display | ✔ | ✔ Graphic LCD | ✔ 2" Graphic LCD | ✔ 2" Graphic LCD |
| Cap buzzer (correct compression) | — | — | ✔ | ✔ |
| Data memory | Last reading only | — | 50 000 readings with date & time | 50 000 readings with date & time |
| PC connectivity / software | — | — | ✔ USB + free software | ✔ USB + free software |
| Offset calibration | — | ✔ | ✔ | ✔ |
| Battery life (no backlight) | Not specified | ~151 hours (2 × AA) | ~77 hours (4 × AA + CR-2032) | ~77 hours (4 × AA) |
| Weight | ~500 g | 700 g | 550 g | 550 g |
| Wheat / maize | ✔ | ✔ | ✔ | — |
| Coffee & cocoa | — | — | ✔ (included in species list) | ✔ Dedicated model |
| Best suited for | Small farms, quick checks | Field use, co-ops, grain traders | Commercial operations, compliance tracking | Coffee importers, roasters, exporters |
Buying Guide
How to choose the right grain moisture meter
The right instrument depends on your crops, the number of measurements you take per day, and whether you need audit-trail data for compliance or trade. Use this decision guide.
You need a quick, affordable field check
You grow wheat, maize or barley on a smaller scale, measure moisture a few times per season, and don't need PC connectivity or detailed record-keeping. You want a simple, battery-efficient instrument with a probe rather than a chamber.
→ Smart Sensor AR991You need professional accuracy for a range of crops
You are a grain buyer, silo manager, commercial farmer or agronomist who needs calibrated results across many grain types — including canola, sunflower, sorghum, millet and maize grits — with temperature compensation and repeatability you can trust.
→ Draminski GMM MiniYou need data logging and compliance documentation
You run a grain trading or export operation, manage multiple silos, or need to provide moisture data records to buyers, auditors or quality certification bodies. 50 000 stored readings with date and time, and Excel / PDF export, give you an auditable measurement trail.
→ Draminski TwistGrain ProYou handle both grain and specialty crops (coffee / cocoa)
Your operation includes green or roasted coffee, parchment beans, or cocoa alongside conventional grains. The TwistGrain Pro includes calibrations for coffee and cocoa species and is the only instrument in the range that serves both worlds in a single device.
→ Draminski TwistGrain ProYou work exclusively in coffee, cocoa, or specialty processing
You are a coffee importer, green bean trader, roastery, or cocoa exporter who needs certified-level moisture measurement for every stage from green beans through to roasted and ground coffee. The dedicated TG-Pro-Coffee delivers ±0.5% accuracy across all 11 coffee and cocoa calibrations.
→ TG-Pro-CoffeeNot sure? Ask our team
If your situation doesn't fit neatly into the above — mixed operations, unusual crops, or a need to calibrate against existing silo instrumentation — our technical team can advise on the best fit before you purchase.
→ Contact EcotaoSouth African Context
Why grain moisture measurement matters in South Africa
Harvest timing
Maize harvested above 35% moisture requires artificial drying, adding significant cost. Harvesting below 12.5% risks unnecessary dry-matter loss and mechanical damage to dry kernels. A moisture meter at the combine allows the operator to confirm the optimal harvest window field by field — particularly important across the heterogeneous soils of the North West, Free State and KwaZulu-Natal grain belts.
Silo intake & grading
SAFEX-linked and co-op silo operations grade maize at 12.5% moisture (Grade 1). Every percent above that level attracts a graded price reduction; every percent below that is effectively lost revenue from overdrying. Regular moisture measurement at intake and during storage prevents costly deductions and protects the farmer's negotiating position on delivery.
Mould and aflatoxin prevention
Maize stored above 14% moisture in South Africa's warm climate is at high risk of Aspergillus mould growth and aflatoxin contamination, which can render entire batches unsaleable and export-ineligible. For wheat, Fusarium-related mycotoxins (particularly deoxynivalenol) proliferate in damp storage. A moisture meter is the primary tool for managing this risk.
Coffee & cocoa quality control
South Africa is an increasingly active market for Kenyan, Ethiopian, and Colombian green coffee imports. Green coffee exported from African origins must meet International Coffee Organization (ICO) standards of 8–12.5% moisture. The TG-Pro-Coffee meters help importers, roasters and quality controllers verify compliance at every handover point in the South African supply chain.
Spontaneous combustion prevention
Wet grain in bulk storage generates heat as micro-organisms respire. At moisture levels above 16–18%, self-heating in maize can reach temperatures that risk spontaneous combustion — a documented cause of silo fires in South Africa. Draminski instruments capable of monitoring large batches with logged, time-stamped readings are a key part of silo safety protocols.
Export certification compliance
Grain destined for export through Durban or Port Elizabeth terminals must meet Codex Alimentarius and buyer-specified moisture limits. Instruments with built-in data logging (GMM Mini / TwistGrain Pro) and PC-exportable records support the traceability documentation required by international buyers and PPECB-regulated export procedures.
Frequently Asked Questions
Grain moisture meter questions answered
What is a grain moisture meter and how does it work?
A grain moisture meter is a handheld instrument that measures the percentage of water in a grain sample — quickly and without laboratory equipment. Professional models use the impedance measurement method: grain is placed in a measuring chamber and a small electrical signal at one or more frequencies is passed through the sample. Because water conducts electricity far better than dry starch, the instrument converts the measured resistance into a moisture percentage within seconds. Draminski's 4-frequency impedance method provides greater stability than single-frequency instruments, particularly across varying grain temperatures.
Why is measuring grain moisture content important in South Africa?
In South Africa, grain sold to SAFEX-linked buyers, cooperatives and millers must meet strict moisture specifications — typically 12.5% for both maize and wheat at Grade 1. Grain above this level attracts price deductions. Grain that is too wet also promotes mould and mycotoxin growth (particularly aflatoxin in maize), causes heating and potential spontaneous combustion in silos, and loses dry matter. A moisture meter allows farmers and silo operators to measure accurately at harvest, before delivery and throughout storage — protecting both quality and income.
What is the difference between the Draminski GMM Mini and the TwistGrain Pro?
The GMM Mini is a compact professional meter with 34 grain types, a 270 ml dosing chamber with dispenser and slide, and approximately 151 hours of battery life. It is ideal for field use, grain buyers, and smaller commercial operations needing reliable readings without data-logging requirements. The TwistGrain Pro is the flagship model: it supports 42 grain species (expandable to 400), uses a 90 ml screw-cap chamber with a buzzer that confirms correct grain compression, stores 50,000 time-stamped readings, connects to a PC for Excel and PDF reporting, and achieves ±0.5% accuracy for standardised grains. Both use 4-frequency impedance measurement for stability across temperature variation.
What moisture content should maize and wheat be at for sale and storage in South Africa?
For commercial sale at South African co-ops and silos, maize and wheat are graded at 12.5% moisture for Grade 1 quality, with price deductions applied at higher moisture levels. For on-farm storage in bag or bulk, target 10–12% for maize and 11–12% for wheat to suppress mould and insect activity. For long-term silo storage, keep grain at or below 12% to prevent heating. Coffee and cocoa have separate targets: green coffee at 10–12%, cocoa beans at 6–8% for export.
Can one moisture meter measure both grain and coffee?
Yes — the Draminski TwistGrain Pro (TG-Pro) includes calibrations for green coffee, roasted coffee, parchment coffee and cocoa alongside its full grain species list, making it a dual-purpose instrument for mixed operations. The dedicated TG-Pro-Coffee is calibrated specifically for 11 coffee and cocoa species at ±0.5% accuracy across all calibrations, and is the instrument of choice for operations working exclusively in the coffee and cocoa supply chain.
Does the Smart Sensor AR991 work for South African crops like maize and sorghum?
Yes. The AR991 includes built-in calibrations for maize, wheat, barley, rice, paddy, sorghum, soybean, peanut, rapeseed, sesame, soybean meal, cotton seed, watermelon seed and fodder — covering most common South African grain and oilseed crops. Its 250 mm probe and backlit LCD make it practical in the field and in dim storage conditions. It is the most affordable grain moisture meter in the Ecotao range and is available in stock for immediate dispatch.
How do I verify my grain moisture meter is giving accurate readings?
Draminski instruments include an offset calibration function that lets users adjust readings against a reference sample dried by the oven method — without sending the unit for factory calibration service. Draminski confirms their instruments do not require periodic service calibration checks. For the AR991, take readings from multiple points in the grain batch and average them, as moisture distribution is rarely uniform. Cross-check periodically against a certified moisture balance at your local co-op or silo intake.
Where can I buy a grain moisture meter in South Africa?
Ecotao supplies grain moisture meters with national delivery from Cape Town. All four instruments — the Smart Sensor AR991, Draminski GMM Mini, Draminski TwistGrain Pro and Draminski TG-Pro-Coffee — are available online via the Ecotao Store. For bulk pricing or technical advice before purchasing, contact us at sales@ecotao.co.za, call +27 21 911 5835, or WhatsApp Zak on 086 142 8716.
Ready to measure with confidence?
All four grain and coffee moisture meters are in stock and available to order via the Ecotao Store, with national delivery across South Africa.