DID YOU KNOW?
Flow meter accuracy isn’t just one number.
Understanding Flow Meter Accuracy: Linearity, Repeatability & Resolution
How % of reading, repeatability, and K-factor resolution shape accuracy.
Know what you’re comparing so your meter stays accurate across the full flow range.
"Did You Know?"
Understanding Flow Meter Accuracy
When selecting a flow meter, accuracy is probably one of the first things you look for. But did you know that accuracy isn’t a single number? It’s actually made up of several factors—each affecting how well your meter performs in real-world conditions. Here’s a quick breakdown to help you make smarter choices.
Linearity
How Error Behaves Across the Flow Range
Linearity describes how much a meter might be off across its rated flow range. You’ll typically see it stated in one of two ways:
- % of Reading (Inherently More Accurate):
The error percentage stays the same no matter the flow rate. - % of Full Scale:
The error is based on the meter’s maximum flow rate—even when you’re operating at much lower rates.
Did you know? At low flow rates, a % of Reading meter can be up to ten times more accurate than a % of Full Scale meter. That’s why the distinction matters so much.
Repeatability
Getting the Same Answer Every Time
Repeatability tells you how consistently a meter measures the same exact conditions—same flow, same liquid, same amount.
Many customers value repeatability even more than absolute accuracy. Why? Because if the meter gives the same reading every time, they can make reliable decisions—even if the reading is slightly off overall.
Think of accuracy as “hitting the bullseye” and repeatability as “grouping your shots tightly.” Great repeatability means predictable results.
Resolution
How Small a Change Your Meter Can Detect
Resolution is all about the smallest measurable increment. Most flow meters use a K-factor, which represents how many pulses are generated per unit of fluid.
A higher K-factor = more pulses per gallon = better detail.
Example
If a meter measures 24.257 gallons:
| K-Factor | Pulses Produced | Displayed Reading |
|---|---|---|
| 10 ppg | 242 | 24.200 gallons |
| 1000 ppg | 24,257 | 24.257 gallons |
Higher resolution = higher accuracy.
Cost
Getting the Right Accuracy for Your Money
It’s true - you get what you pay for. But sometimes two meters look the same on paper because they share the same accuracy spec. That’s where it pays to dig deeper:
- If one meter costs less, chances are you’re comparing % of Reading vs. % of Full Scale.
- Need consistent readings? Prioritize repeatability.
- Need finer measurement detail? Look for a higher K-factor (or higher pulse frequency).
And here’s a bonus fact: All FLOMEC meters are % of Reading, giving you significantly better accuracy across your full flow range.
Takeaway
When choosing a flow meter, accuracy is more than a single number. Consider linearity, repeatability, and resolution—and make sure you’re paying for the performance you truly need.