Overview
ISO 7700-1:2008 - "Food products - Checking the performance of moisture meters in use - Part 1: Moisture meters for cereals" - specifies a standard method for checking the in-service performance of moisture meters used to measure moisture content of cereal grains. It is intended for periodic performance checks (not for pattern approval or initial calibration) and provides criteria to decide whether a moisture meter requires revision or repair.
Key topics and requirements
- Scope: Performance checking of moisture meters for cereal grains in operational conditions. Not applicable to pattern approval or initial calibration.
- Reference methods: Uses routine reference methods - ISO 712 for most cereals and ISO 6540 for maize - as the true moisture content benchmark.
- Apparatus: Bottles with airtight seals, sample divider, sieves (per ISO 5223), thermometer, and routine moisture-determination equipment.
- Sample selection & preparation:
- Use at least two cereal species (or two grain types for maize/rice) with two samples each having markedly different moisture contents within the meter’s range.
- Clean and homogenize samples using specified sieves; keep test sample volumes at ~2/3 bottle capacity to avoid moisture exchange.
- Procedure:
- Take an initial reference test portion (B) and determine moisture content by ISO 712/6540.
- Perform multiple measurements with the moisture meter on the test portion (A−B), ensuring thermal equilibrium (recommended 15–25 °C) between meter and sample.
- Take a final reference test portion (C) and re-determine moisture content to compute the true value (mean of initial and final).
- Expression of results:
- Calculate differences between each meter reading and the true value.
- Repeat the test if the two reference determinations differ by more than 0.3% (mass fraction).
- Maximum permissible errors (MPEs):
- Cereals (other than maize, rice, sorghum): ±0.7% for w ≤ 10%; for w > 10%: ±(0.4% + 3% of w).
- Maize, rice, sorghum: ±0.8% for w ≤ 10%; for w > 10%: ±(0.4% + 4% of w).
- Examples and calculation guidance provided in the standard.
- Test report: Must identify the meter, samples, test conditions (temperature), measurements, and any incidents affecting results.
Applications and users
This standard is practical for:
- Grain handlers, storage operators, millers and processors conducting routine quality control.
- Equipment maintenance technicians and service providers assessing instrument performance in use.
- Quality managers and auditors ensuring moisture measurement reliability for inventory valuation, storage decisions and food safety.
- Laboratories performing on-site verification before deciding on repairs or recalibration.
Keywords: ISO 7700-1:2008, moisture meters, cereals, moisture content, checking performance, ISO 712, ISO 6540, maximum permissible error.
Related standards
- ISO 712 - cereals routine reference method (moisture)
- ISO 6540 - maize moisture determination
- ISO 5223 - test sieves for cereals
- OIML R59 - pattern approval recommendations for moisture meters (referenced for approval contexts)