If you own scales, you will eventually hear about calibration test weights M1 class. These are the certified reference weights technicians use to check that platform scales, floor scales, crane scales and weighbridges read correctly. Understanding them helps you judge whether your scale was calibrated properly, and whether you should keep your own weights on site.
Here are calibration test weights M1 class explained in plain terms: what weight classes mean, why M1 is the common choice for trade scales, and how to look after test weights in Nigerian conditions.
What are calibration test weights?
A test weight is a mass made to a known value within a tight tolerance. When a technician places it on a scale, the reading should match that value. If it does not, the scale is adjusted until it does.
For the result to be trusted, the test weights themselves must be accurate and traceable, meaning they have been compared against higher-accuracy reference weights in an unbroken chain. That traceability is what a calibration certificate for the weights shows.
Understanding weight classes
Internationally, test weights are grouped into accuracy classes under the OIML system. From most to least accurate, the classes are:
- E1 and E2: very high accuracy, used for analytical balances and reference labs
- F1 and F2: high accuracy, used for precision balances and checking lower-class weights
- M1, M2 and M3: medium accuracy, used for industrial and trade scales
Each class has a maximum permissible error for each nominal value. A 20 kg E2 weight is made far more precisely than a 20 kg M1 weight, and costs much more. The right class depends on the scale you are checking.
Calibration test weights M1 class explained: why M1 suits trade scales
Most commercial scales in Nigeria, from shop platform scales to warehouse floor scales and weighbridges, are medium-accuracy instruments. M1 weights are accurate enough to test them properly, robust enough for daily handling, and practical in larger sizes.
That is why calibration test weights M1 class are the standard working weights for:
- Platform and floor scales in warehouses, markets and factories
- Crane scales in steel yards and depots
- Livestock and gas cylinder scales
- Weighbridges, where hundreds or thousands of kilograms of weights are used
For high-readability lab balances, M1 is not enough. Those need F or E class weights matched to the balance.
Common M1 weight sizes and materials
Small and medium weights
Sets from 1 kg to 20 kg are used for counter, bench, platform and floor scales. Our Class M1 calibration test weights set, 1 kg to 20 kg covers most small and medium scales. These are usually stainless steel or coated cast iron with a handle or a rectangular block shape that stacks safely.
Large weights for weighbridges
Weighbridges and heavy floor scales need much larger references. 500 kg and 1,000 kg cast-iron test weights are lifted by forklift or crane and placed at different points on the deck to check each section. Read our guide to weighbridge calibration certificates to see how this fits into the full process.
How test weights are used in a calibration
A typical calibration of a floor or platform scale includes:
- Zero check: the scale reads zero with nothing on it
- Linearity test: weights are added in steps up the range and readings compared
- Eccentricity test: a weight is placed at the corners and centre to check every load cell section reads the same
- Repeatability test: the same weight is placed several times to check consistency
- Adjustment and record: the scale is adjusted if needed and results recorded
For trade use, the scale is then verified so the owner holds a Weights and Measures certificate of verification.
Should you buy your own test weights?
Owning a few M1 weights is a smart move if you:
- Run many scales across one site, such as a factory or warehouse
- Weigh high-value goods where small errors are costly
- Want to check scales daily or weekly between official calibrations
- Operate crane scales, such as a 3 tonne digital crane scale, that are exposed to knocks
A quick morning check with a known weight catches problems early. It does not replace certified calibration, but it tells you when to call a technician.
Caring for test weights
M1 weights only stay accurate if they are looked after:
- Store them clean and dry, off the floor, in a case or rack
- Do not drop them; chips and dents change the mass
- Clean off dust, grease and rust with a dry cloth
- Never adjust, drill or paint them yourself
- Have them recertified on a regular schedule
Humidity in coastal cities like Lagos, Warri and Port Harcourt can cause rust on cast iron. Keep them covered and treat any surface corrosion promptly.
Calibration services from Kira Scales
Kira Scales provides certified scale and weighbridge calibration across all 36 states and the FCT, with the Weights and Measures certificate of verification at least once a year and more frequent checks if you choose. We bring the right test weights for the job, from small sets to large blocks for weighbridges. See our products for weights and scales.
We do not list figures here; see the product page for current pricing or request a quote. Contact Kira Scales or call or WhatsApp +234 803 435 4829 to book a calibration or buy test weights.
Frequently Asked Questions
What does M1 class mean on a test weight?
M1 is a medium accuracy class under the OIML system. It is the usual class for checking trade scales such as platform, floor and crane scales and weighbridges.
Can I use M1 weights for a laboratory balance?
No, not for analytical or high-precision balances. These need higher-class weights, typically F or E class, matched to the balance readability.
How often should test weights be recertified?
On a regular schedule, and sooner if they are dropped, damaged or corroded. Your calibration provider can advise on the interval.
Do test weights need a certificate?
Yes. A certificate shows the weights are traceable and within tolerance for their class, which gives meaning to the scale calibration.
What weights are used to calibrate a weighbridge?
Large cast-iron test weights, often 500 kg or 1,000 kg each, are placed across the deck, sometimes with known-weight vehicles for higher loads.
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