采购称重传感器，参数表里总有一个"C3"字样。有人以为数字越大越高级，看到 C4、C5 就心动，殊不知多花一倍钱买了个工业上用不上的精度。这篇文章把精度等级讲清楚。
C3 到底是什么？
称重传感器的精度等级，源自国际法制计量组织（OIML）的划分。常见的等级有 C3、C4、C5，其中"C"代表称重传感器（Cell），数字代表检定分度数。
- C3 = 3000 个分度
- C4 = 4000 个分度
- C5 = 5000 个分度
数字越大，代表传感器能被"切分"得越细，精度越高。
C3 精度到底够不够用？
判断精度够不够，用这个公式：
最小分辨重量 = 传感器量程 ÷ 分度数
举个实际例子：
| 传感器量程 | C3 最小分辨 | C4 最小分辨 | C5 最小分辨 |
|---|
| 100kg | 33g | 25g | 20g |
| 500kg | 167g | 125g | 100g |
| 1000kg | 333g | 250g | 200g |
对工业称重来说：
- 检重秤：称重范围几十克到几十公斤，C3 分辨到 33g，足够
- 包装秤：称重范围几十克到几百公斤，C3 足够
- 配料系统：配比误差控制在 0.1%～0.5%，C3 足够
- 反应釜称重：监控吨级物料，C3 分辨到 167g～333g，绰绰有余
结论：工业场景 99% 用 C3 就够。 C4、C5 主要给实验室天平、精密计量、高精度配料用，价格高出不少。
精度等级高，不等于传感器一定好
这是很多人容易误解的地方。精度等级只是一个"量程切分能力"的指标，它不直接等于"准不准"。
真正决定传感器准不准的，是这几个指标：
- 综合误差：优秀产品 ≤±0.02% F.S
- 蠕变：长时间加载下的稳定性
- 温漂：温度变化下的精度保持能力
一只 C3 但综合误差、蠕变、温漂都优秀的传感器，实际表现可能比一只 C4 但稳定性差的传感器更好。
选精度的正确姿势
- 先明确量程：设备最大称重多少
- 算最小分辨：量程 ÷ 3000，看够不够你的精度需求
- 不够再升级：如果 C3 的分辨不够，再考虑 C4/C5
- 重点看稳定性：综合误差、蠕变、温漂这三个指标比精度等级更关键
一句话总结
工业称重选 C3，别为用不上的精度多花钱。真正该较真的是综合误差、蠕变、温漂这些"长期稳定性"指标。
When sourcing load cells, there is always a "C3" label in the parameter table. Some people think bigger numbers are more advanced and get excited seeing C4 or C5, unaware that they would spend double for an accuracy class that industrial use doesn't need. This article explains accuracy classes clearly.
What exactly is C3?
Load cell accuracy classes originate from the International Organization of Legal Metrology (OIML). Common classes are C3, C4 and C5, where "C" stands for load cell (Cell) and the number represents the verification interval count.
- C3 = 3000 divisions
- C4 = 4000 divisions
- C5 = 5000 divisions
The bigger the number, the finer the load cell can be "divided", and the higher the accuracy.
Is C3 accuracy enough?
To judge whether accuracy is enough, use this formula:
Minimum resolution = load cell capacity ÷ division count
A practical example:
| Load cell capacity | C3 min resolution | C4 min resolution | C5 min resolution |
|---|
| 100 kg | 33 g | 25 g | 20 g |
| 500 kg | 167 g | 125 g | 100 g |
| 1000 kg | 333 g | 250 g | 200 g |
For industrial weighing:
- Checkweigher: weighing range from tens of grams to tens of kilograms; C3 resolving to 33 g is enough
- Packing scale: weighing range from tens of grams to hundreds of kilograms; C3 is enough
- Batching system: ratio error controlled within 0.1% ~ 0.5%; C3 is enough
- Reactor weighing: monitoring ton-level materials; C3 resolving to 167 g ~ 333 g is more than enough
Conclusion: 99% of industrial scenarios only need C3. C4 and C5 are mainly for laboratory balances, precision metrology and high-precision batching, at a much higher price.
A high accuracy class does not mean the load cell is necessarily good
This is a common misunderstanding. The accuracy class is only an indicator of "range-division capability"; it does not directly equal "accuracy".
The indicators that truly determine whether a load cell is accurate are:
- Combined error: excellent products ≤ ±0.02% F.S
- Creep: stability under long-term loading
- Temperature drift: accuracy retention under temperature changes
A C3 load cell with excellent combined error, creep and temperature drift can actually perform better than a C4 load cell with poor stability.
The right way to select accuracy
- First determine the capacity: the equipment's maximum weighing capacity
- Calculate minimum resolution: capacity ÷ 3000, and see if it meets your accuracy needs
- Upgrade if insufficient: if C3 resolution is not enough, consider C4/C5
- Focus on stability: combined error, creep and temperature drift matter more than the accuracy class
One-sentence summary
For industrial weighing choose C3; don't pay for accuracy you won't use. What really deserves scrutiny are the "long-term stability" indicators: combined error, creep and temperature drift.