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Knowledge Base

Glossary

Terms used across automated particle counting, robotic Houillon viscometry, ISO 11171 calibration and CINRG instrumentation — defined by the CINRG technical team.

Built to standards
ASTM D7647 · D7279 · D5185
ISO 11171:2022
NIST SRM 2806d traceable

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ACFTD AC Fine Test Dust
The original test dust used to calibrate optical particle counters under ISO 4402 from 1960 until 1999. Particle size was based on the longest chord length of the dust, and the material was not NIST-traceable. ACFTD was discontinued in 1998 and replaced by ISO Medium Test Dust (MTD).
Annex A – E (ISO 11171) ISO 11171
The factory-calibration procedures defined by ISO 11171: Annex A (sensor noise determination via Super Clean Fluid until counts fall below 1/sec), Annex B (coincidence error using a linear-regression of dilutions of primary standard), Annex C (flow-rate limits showing <3% deviation), Annex D (resolution at 10µm), and Annex E (accuracy verification using 1 mg/mL Ultra Fine Test Dust against the certified table values).
AS4059 SAE
SAE Aerospace Standard 4059 — the modern aviation/aerospace cleanliness coding system used for hydraulic fluids such as Skydrol LD-4 and 500B-4. Reported as either a Differential code (6–14, 14–21, 21–38, 38–70, >70µm) or a Cumulative code (>4, >6, >14, >21, >38, >70µm). AS4059 is calibrated to ISO 11171 and uses MTD calibration fluid; the differential form is equivalent to the legacy NAS 1638 contamination class.
ASTM D5185 ASTM
The Standard Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Specifies weight/volume sample preparation; most commercial labs run a volume/volume modification (D5185m). See CS-SDS-2 sample dilution system.
ASTM D5185m ASTM
The volume/volume modification of ASTM D5185 used by most commercial oil-analysis laboratories. A new ASTM method has been proposed to formalize volume/volume preparation of standards and samples for oil analysis.
ASTM D7279 ASTM
The Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids by Automated Houillon Viscometer. The current revision, D7279-14, governs the operation of automated Houillon-type capillary viscometers at 40°C and 100°C. The CS-HVA-2 and CS-HVA-4 robotic viscometer systems are designed to meet D7279-14.
ASTM D7647 ASTM
The Standard Test Method for Automatic Particle Counting of Lubricating and Hydraulic Fluids Using Dilution Techniques to Eliminate the Contribution of Water and Interfering Soft Particles by Light Extinction. First published 2010. Defines auto-dilution as the workflow for optical particle counting in used lubricants. CINRG’s entire CS-APC instrument line is built around D7647.
Auto-dilution ASTM D7647
Automatic in-line dilution of an oil sample with a masking solvent (typically 75/25 or 90/10 toluene/IPA) prior to optical particle counting. Auto-dilution is the central technique of ASTM D7647: it removes interference from soft particles (water, varnish precursors, additives) and lets a single optical sensor handle both very clean and very dirty samples without manual pre-filtration.

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Batch file
The CSV-format file that drives a CINRG instrument run. Contains per-sample fields (sample number, position, priority, expected viscosity, dilution ratio, processing parameter set, operator ID) and is either built inside the CINRG software or imported from a LIMS or Excel. Editable while a run is in progress to add, remove or re-prioritize samples.
Beta ratio filtration
A filter-performance metric — the ratio of upstream to downstream particle counts at a given size (e.g., β5 = 200 means 200 particles >5µm enter for every 1 that passes). The transition from NIST SRM 2806a to 2806b inflated apparent counts by 40–75%, mathematically depressing reported beta ratios for the same physical filter; instrument manufacturers and end users had to recalibrate to ISO 11171:2016 to restore meaningful beta numbers.

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Calibration fluid (primary)
A NIST-issued standard reference material certified for use in sizing-calibration of optical particle counters under ISO 11171. Sold by NIST itself (the SRM 2806 series), produced under contract, certified by external parties or by interlaboratory study, and expensive (about US$4,742 for 3 × 400 mL of SRM 2806d).
Calibration fluid (secondary)
A calibration fluid prepared by a certified manufacturer with traceability back to the NIST primary — the everyday-use form for commercial labs. CINRG’s secondary line is CINSTAN, with its 2806d-traceable component priced at roughly a quarter of the primary.
Capillary tube ASTM D7279
The narrow-bore glass tube that is the heart of a Houillon viscometer. Sample falls through the capillary under gravity at controlled temperature; the time to fall between two optical sensors, multiplied by the tube’s factor, gives kinematic viscosity. Each tube has a working viscosity range; the CS-HVA software selects the right tube for each sample using fuzzy logic.
Carry-over
Residual contamination from one sample that is detected in the following sample because of imperfect cleaning between runs. Specified for the CS-SDS-2 sample dilution system as <0.1% (i.e., <2 ppm following a 2,000 ppm standard); the CS-HVA robotic viscometer minimises carry-over via syringe wash station, drying pad, and limited needle penetration into samples.
CINSTAN CINRG
The CINRG family of NIST-traceable secondary calibration, verification and process-control fluids for optical particle counters, compliant with ISO 11171:2022. The product line includes the Calibration Kit (CS-CINSTAN-CFK), Process Control Standards (CS-CINSTAN-PCS), Verification Fluids (CS-CINSTAN-VF), Super Clean Fluid (CS-CINSTAN-SCF), and PSL40/60/80 polystyrene-latex monosphere blends. See CINSTAN.
Coincidence threshold
The particle concentration at which two or more particles in the laser view volume are counted as a single larger particle, distorting both the count and the size distribution. The KLOTZ LDS 45/50 sensor has a 4µm coincidence threshold of 25,000 particles/mL on an undiluted sample and 50,000 particles/mL at 1:1 dilution. Auto-dilution effectively pushes the practical coincidence ceiling much higher.
cSt centistoke
The unit of kinematic viscosity (1 cSt = 1 mm²/s). Common reporting points are KV40 (kinematic viscosity at 40°C, where most industrial oils are specified) and KV100 (at 100°C, used for engine oil and viscosity index). The CS-HVA reports both.
Cumulative count
The number of particles per millilitre at or above a given size threshold (e.g., >4µm, >6µm, >14µm). ISO 4406:1999 and the cumulative form of SAE AS4059 both use cumulative counts.

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Differential count
The number of particles per millilitre within a size band (e.g., 6–14, 14–21, 21–38µm). NAS 1638 and the differential form of SAE AS4059 both use differential counts. Differential and cumulative counts are arithmetically interconvertible.
Dilution ratio
The volume ratio of oil to solvent during ASTM D7647 sample dilution, expressed as oil:solvent. CINRG instruments support 1:0 (neat) through 1:9 (one part oil, nine parts solvent), settable per sample in the batch file. The system corrects all reported counts to undiluted-equivalent automatically.
Dq (Internal Variance Limit) ISO 11171, ASTM D7647
The repeatability metric for a series of repeat counts on the same sample, calculated as Dq = (Xmax − Xmin) / Xavg. ISO 11171 and ASTM D7647 each specify default maximum allowable Dq values; CINRG software ships with these values pre-loaded and end users may tighten them but not relax them. Reported per run as IVL:PASS / IVL:FAIL.

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Fuzzy logic tube selection CS-HVA
The CS-HVA software routine that matches each sample to the correct viscometer capillary tube based on the expected viscosity in the batch file. If the right-factor tube is busy, the system queues the sample and continues; if no suitable tube is currently in service, the sample is skipped and retried later when a matching tube is free. Eliminates the operator-error mode of manually selecting the wrong tube.

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Ghost particle
An informal name for a soft particle — a non-abrasive species in lubricating oil that is detected as a particle by an optical counter but does not represent wear-causing contamination. The category includes water, insoluble oxidation by-products such as varnish precursors, dispersants, friction modifiers, and anti-foam additives such as polydimethylsiloxane (PDMS). See CINRG’s ghost-particles study.

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Houillon viscometer ASTM D7279
A capillary-tube viscometer geometry, originally developed in France, designed for automated kinematic-viscosity measurement at 40°C and 100°C. ASTM D7279 governs the use of automated Houillon viscometers in commercial labs. The CS-HVA family adds an XYZ robot, syringe pump, and wash station to deliver up to 1,200 measurements per shift on a 4-bath system.

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ICP-AES ASTM D5185
Inductively Coupled Plasma Atomic Emission Spectrometry — the standard technique for elemental analysis of used and unused lubricating oils (wear metals, additive metals, contaminants). Sample dilution is performed upstream of the ICP; the CS-SDS-2 automates this step under modified ASTM D5185 (D5185m).
ILS interlaboratory study
A multi-laboratory round-robin used to certify a primary calibration fluid or to establish a precision statement for an ASTM method. NIST SRM 2806d was the first NIST particle-count standard certified by ILS rather than by single-lab SEM imaging. CINRG participated in the ILS for the next two batches (SRM 2806e and 2806f) alongside Atmus, CFPC, D-2 Inc., Donaldson, NIST, Pamas and Stanhope-Seta — 14 sensors across 4 countries.
Internal Variance Limit (IVL)
The maximum allowable difference between repeat particle-count runs on the same sample, expressed as a percentage of the mean (Dq). See Dq.
ISO 11171 ISO
The international standard for sizing-calibration of optical particle counters used in hydraulic-fluid and lubricant cleanliness reporting, using a NIST-traceable Medium Test Dust primary standard. Major revisions: 11171:1999 (ISO MTD introduced), 11171:2016 (allowed dual reporting in µm(b) and µm(c)), 11171:2022 (current; µm(b) discontinued, ILS-based certification mandated).
ISO 4402 ISO
The legacy international standard for particle-counter calibration, in force from 1960 until 1999. Used ACFTD as the test dust and counted particles based on longest chord length. Replaced by ISO 11171 when ACFTD was discontinued.
ISO 4406 ISO
The international standard for coding the cleanliness of a lubricated component — the “ISO Cleanliness Code.” ISO 4406:1987 reported particle counts at >5µm and >15µm as a two-tier code. ISO 4406:1999 expanded to a three-tier code at >4µm(c) / >6µm(c) / >14µm(c), and is the currently used form.
ISO MTD ISO 11171
ISO Medium Test Dust — the NIST-traceable test dust used as the basis for ISO 11171 calibration since 1999. Particle size is defined by the area of cross-section (projected area equivalent diameter) rather than the longest chord. Issued as the SRM 2806 family of primary calibration fluids.
Isopropanol (IPA) ASTM D7647
The polar component of the recommended D7647 dilution solvent. IPA dissolves up to 2% water at a 1:1 dilution and helps mask water-derived ghost-particle counts. Standard CINRG diluent: 75/25 toluene/IPA. Upcoming D7647 Procedure A: 90/10 toluene/IPA.

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JIS B 9933 JIS
The Japanese Industrial Standard companion to ISO 11171. CINRG instruments configured for Japanese laboratories meet JIS B 9933 requirements as part of the same calibration workflow.

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Kinematic viscosity
The ratio of dynamic viscosity to density — how easily an oil flows under gravity. Reported in centistokes (cSt) at a specified temperature, typically KV40 or KV100. Measured under ASTM D7279 by Houillon viscometer (gravity-flow capillary), or under ASTM D445 by U-tube capillary.
KLOTZ LDS 45/50
The laser-diode-based light-blocking sensor used in CINRG CS-APC-3 and CS-APC-22M particle counters. Measuring range 4µm to 70µm (oil calibration range 3µm to 200µm), 4µm coincidence threshold 25,000 particles/mL undiluted, 450µm × 500µm view-volume cell, calibrated at 30 mL/min flow rate.
KV40 / KV100
Kinematic viscosity at 40°C and 100°C respectively. KV40 is the headline industrial-oil number; KV100 drives engine-oil grading and viscosity index. The CS-HVA robotic system reports both.

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Light extinction optical particle counting
The light-blocking detection mode used in CINRG particle counters: a particle moving through the laser beam reduces transmitted light at the photodiode in proportion to its projected area. The voltage drop is converted to a particle-size value via the calibrated channel table. Light extinction is the standard mode named in ASTM D7647.
Light scattering optical particle counting
An alternative detection mode in which scattered (rather than transmitted) light is measured. More sensitive at very small sizes but more easily fooled by water droplets and refractive-index differences — one reason ASTM D7647 dilution is critical when scattering sensors are used. Both extinction and scattering sensors were represented in the recent NIST SRM 2806e/2806f ILS.
LIMS laboratory information management system
The lab’s sample-tracking and reporting platform. CINRG instruments accept CSV batch files generated by the LIMS, and write CSV result files in formats configurable from the LIMS side — including ISO 4406, AS4059, raw counts, solvent background, dilution ratio and IVL pass/fail.

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Masking solvent ASTM D7647
A solvent that, when used to dilute an oil sample before particle counting, dissolves or disperses soft particles (water, varnish precursors, additives) so they do not register at the optical sensor. CINRG’s preferred masking solvent is 75/25 toluene/IPA; non-masking solvents like kerosene and Varsol are not effective.
Medium Test Dust (MTD) ISO 11171
The NIST-certified test dust that defines the µm(c) particle-size scale used in ISO 11171 calibration. Issued as the SRM 2806 primary calibration fluid family. Replaced ACFTD in 1998–1999.
µm(b)
A transitional particle-size scale tied to the SRM 2806b certification. Allowed under ISO 11171:2016 alongside µm(c), with a fixed conversion factor dc = 0.898 db. Discontinued by ISO 11171:2022.
µm(c)
The current particle-size scale used in ISO 11171 calibration, tied to NIST SRM 2806a / 2806d certifications. ISO 4406:1999 cleanliness codes are reported as cumulative counts at >4µm(c), >6µm(c) and >14µm(c).
MPC membrane patch colorimetry
A quantitative measure of insoluble varnish in lubricating oil based on filter-patch coloration, expressed as ΔE. High MPC values are correlated with inflated optical particle counts on undiluted samples — a classic ghost-particle signature. ASTM D7647 dilution mitigates this effect.

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NAS 1638 SAE
The legacy aerospace cleanliness coding standard from 1987, calibrated to ISO 4402 / ACFTD and reported as a single “contamination class.” Differential counts in 5–15, 15–25, 25–50, 50–100 and >100µm bands. Superseded by SAE AS4059, but still requested by some specifications — CINRG instruments will report it on demand.
NIST SRM 2806 family NIST
The NIST Standard Reference Material series of MTD-based primary calibration fluids: SRM 2806 (1997–2004, filter patch / ESM), SRM 2806a (2013, filter patch / ESM, statistically equivalent to 2806), SRM 2806b (2014–2020, filter patch / SEM, certified counts ~40%+ higher than 2806a), SRM 2806d (current, ILS certification). SRM 2806e and 2806f are the next two batches; CINRG participated in the certifying ILS.

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Optical particle counter (OPC)
An instrument that determines particle size and concentration in a fluid by passing a metered volume past a laser beam and measuring the resulting voltage pulses on a photodiode (light-extinction mode) or scattering detector (scattering mode). All CINRG CS-APC instruments are OPCs configured for the lubricating-oil application under ASTM D7647.

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PDMS polydimethylsiloxane
A silicone-based anti-foam additive widely used in lubricants. PDMS produces strong soft-particle / ghost-particle counts on undiluted optical particle counters and is one of the additives most reliably masked by 75/25 toluene/IPA dilution. Aggressive sub-micron filtration to chase PDMS-derived false counts strips the additive package from the oil.
Primary calibration fluid
A NIST-issued reference material for sizing-calibration of optical particle counters under ISO 11171. See Calibration fluid (primary) and NIST SRM 2806 family.
Process Control Standard (PCS)
A reference fluid run repeatedly during normal sample processing and trended against upper and lower control limits to confirm that the instrument is in statistical control. CINRG’s offering is CS-CINSTAN-PCS, a low-cost NIST-traceable standard in ISO 40 white oil. Sample numbers prefixed (or suffixed) with “PCS” trigger automatic limit-checking against the system’s configured 4/6/14µm thresholds.
PSL polystyrene latex
Polystyrene-latex monospheres used to calibrate the larger particle-size channels (38µm and 70µm) on optical particle counters. PSL spheres are unaffected by the SRM 2806 transition because their certification is independent of MTD. CINSTAN supplies PSL40, PSL60 and PSL80 blends in Super Clean Fluid.

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RM2806 / SRM2806
RM (Reference Material) and SRM (Standard Reference Material) are NIST’s designations for, respectively, secondary and primary reference fluids in the 2806 family. Numbers a, b, d, e, f denote successive batches; gaps in the alphabetical sequence (e.g., no 2806c) reflect batches that were planned but not certified.

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Sensor noise ISO 11171 Annex A
The baseline voltage detected by the LDS sensor when ultra-clean fluid is flowing past the laser, with no real particles present. The CINRG sensor-noise procedure measures this threshold (in mV) using Super Clean Fluid through a temporary tubing path before any annual sizing calibration. The current 4µm calibration mV setting must comfortably exceed the noise threshold.
Signal-to-noise ratio (SNR) CINRG calibration
The ratio of the 4µm mV channel setting to the sensor-noise mV threshold. CINRG’s internal acceptance: SNR ≥ 1.5 is preferred; 1.2 is the minimum acceptable. An SNR below 1.2 indicates the sensor needs evaluation or service before sizing calibration can be attempted.
Soft particle
A non-abrasive species in lubricating oil that is detected as a particle by an optical counter. Synonym: ghost particle. See Ghost particle.
Solvent verification ASTM D7647
The CINRG software routine that measures the cleanliness of the dilution solvent batch before testing begins. Solvent is loaded into position 1 (system flush) and position 2 (measurement); several measurements are taken, validated against editable system parameters, and the average is stored as the solvent background counts used to correct subsequent sample results.
SRM NIST
Standard Reference Material — a NIST-issued primary calibration fluid. The 2806-series SRMs are the basis for ISO 11171 calibration of optical particle counters.
Super Clean Fluid (SCF)
An ultra-clean carrier fluid used as the diluent base for CINSTAN reference materials and as the rinsing fluid for sensor-noise verification. Available separately as CS-CINSTAN-SCF or as part of the Calibration Kit. SCF has no expiry date.

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Toluene ASTM D7647
The non-polar component of the recommended D7647 dilution solvent. Toluene re-solubilizes varnish precursors and large-molecule additives that would otherwise be detected as soft particles. Used in 75/25 (current standard) or 90/10 (Procedure A draft) blend with isopropanol.
Tube factor
The calibration constant for an individual Houillon viscometer capillary tube, relating measured fall time to kinematic viscosity. Multi-point calibration produces a more accurate factor across a wider viscosity band, with particularly large impact on KV100 reporting. Each tube’s factor is stored in the CS-HVA software per bath.

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UFTD ultrafine test dust
The fine-grade test dust used in ISO 11171 Annex E for verification of particle-count accuracy. A 1 mg/mL UFTD sample is measured at 6 sizes between 5 and 15µm; values must fall within Table A.1 of the standard. UFTD verification is part of every factory calibration.
Upper / Lower Control Limit (UCL / LCL)
The user-defined boundaries above and below the certified value of a Process Control Standard, beyond which the run is flagged as out of statistical control. CINRG software supports UCL/LCL configuration per particle-size channel (4, 6, 14µm) for particle counters and per bath/tube for the CS-HVA viscometer system.

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Varnish precursor
An insoluble oxidation by-product in lubricating oil that is the early-stage indicator of varnish formation. Varnish precursors are classic soft particles — they generate inflated optical-counter readings on undiluted samples and are largely re-solubilized by toluene-based dilution under ASTM D7647.
Verification fluid
A NIST-traceable reference material used to confirm that the calibration of an optical particle counter is still valid — typically run as a single check at the start of a measurement campaign rather than as the per-batch process-control sample. CINRG’s offering is CS-CINSTAN-VF, supplied as 4 × 400 mL bottles per pack.
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