---
title: "ISO 11171 Measurement Standard | Aethair"
description: "ISO 11171:2022, Hydraulic fluid power — Calibration of automatic particle counters for liquids, sets how automatic particle counters for hydraulic fluids,…"
url: https://aethair.io/standards/iso_11171/
---

Measurement method · ISO

# ISO 11171: calibration of automatic particle counters for liquids

**ISO 11171:2022**, Hydraulic fluid power — Calibration of automatic particle counters for liquids, sets how automatic particle counters for hydraulic fluids, fuels, and oils are calibrated for particle size, resolution, and counting performance. Sizes calibrated this way carry a **"(c)" suffix**, as in the 4 µm(c), 6 µm(c), and 14 µm(c) channels of an ISO 4406 cleanliness code.

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At a glance

**ISO** Measurement method

1 parameter

[Fluid Particle Count (ISO 4406)](https://aethair.io/parameters/particle_count_fluid/)

[Official text from ISO](https://www.iso.org/standard/82850.html)

Who uses it

## Who Uses It

Makers and users of liquid particle counters in hydraulics, lubrication, and diesel and aviation fuel quality, and the laboratories that calibrate them.

Monitoring

## How It Relates to Monitoring

An inline counter calibrated to ISO 11171 reports particle counts whose sizes mean the same as a laboratory's, so the [ISO 4406](https://aethair.io/standards/iso_4406/) code it derives can be compared with the cleanliness target set for the system and trended over time.

Devices

## Instruments Built to ISO 11171

Instruments in the sensor catalog that follow this method. Each connects to Environet through a Thiamis gateway.

Instruments built to it

[**Parker icountPD** Fluid & Fuel Quality](https://aethair.io/sensors/parker-fluid-fuel-quality/)

Solutions

## Solutions That Rely on ISO 11171

### [Hydraulic & Fuel Cleanliness](https://aethair.io/solutions/industrial-fluids/)

ISO 4406 oil cleanliness and aviation fuel

[All solutions](https://aethair.io/solutions/)

Questions

## ISO 11171 FAQ

What does the "(c)" after a particle size mean?

That the size was calibrated under ISO 11171, as in the 4 µm(c), 6 µm(c), and 14 µm(c) channels of an ISO 4406 code.

Which fluids does ISO 11171 apply to?

Hydraulic fluids, aviation and diesel fuels, engine oil, and other petroleum-based fluids.

How does ISO 11171 relate to ISO 4406?

ISO 11171 calibrates the particle counter; ISO 4406 turns the calibrated counts into a cleanliness code.