ATAGO PAL-91S Portable Digital Ethylene Glycol Refractometer

Overview

The ATAGO PAL-91S Portable Digital Ethylene Glycol Refractometer is an optical measurement instrument engineered for rapid, field-deployable quantification of ethylene glycol (EG) concentration in aqueous coolant solutions. It operates on the principle of critical-angle refractometry: light passes through a prism in contact with the sample, and the resulting refraction angle—dependent on the solution’s refractive index—is converted into a calibrated mass percentage (w/w %) of ethylene glycol. Built-in Automatic Temperature Compensation (ATC) ensures measurement stability across ambient temperatures from 10°C to 100°C, eliminating manual correction and supporting consistent readings in dynamic environments such as automotive service bays, HVAC maintenance sites, or industrial cooling loop inspections. Unlike generic refractometers, the PAL-91S integrates a proprietary algorithm that simultaneously calculates and displays the corresponding freezing point (°C) based on the measured EG concentration—enabling immediate assessment of freeze protection performance without external lookup tables or empirical interpolation.

Key Features

• Optimized optical path design with high-stability sapphire prism for long-term repeatability and resistance to chemical abrasion from glycol-based coolants
• Digital LCD display with 0.2% resolution for ethylene glycol concentration and ±1°C freezing point readout
• IP65-rated enclosure providing dust-tight operation and protection against low-pressure water jets—suitable for use in humid engine compartments or outdoor mechanical rooms
• Compact form factor (5.5 × 3.1 × 10.9 cm) and lightweight construction (100 g) enabling one-handed operation and integration into routine preventive maintenance workflows
• Two AAA battery power system delivering >10,000 measurements per set under typical usage conditions; no external charger or USB dependency required
• Factory-calibrated using NIST-traceable reference standards; user calibration verification supported via supplied EG standard solution (optional)

Sample Compatibility & Compliance

The PAL-91S is validated for use with monoethylene glycol (MEG) and diethylene glycol (DEG) aqueous solutions, including commercially formulated antifreeze/coolant mixtures containing corrosion inhibitors, dyes, and surfactants. It is not intended for use with propylene glycol-based coolants or non-aqueous heat transfer fluids. Measurements comply with ASTM D1120 (Standard Test Method for Boiling Point of Engine Coolants) and ISO 2808 (Paints and Varnishes — Determination of Film Thickness), where refractive index serves as a proxy for composition analysis in quality control contexts. While the device itself does not generate audit trails or electronic records, its measurement output supports GLP-compliant documentation when paired with standardized lab notebooks or LIMS-integrated reporting procedures.

Software & Data Management

The PAL-91S is a standalone, embedded-system instrument with no Bluetooth, Wi-Fi, or PC connectivity. All data are displayed in real time on the integrated LCD screen and must be manually recorded. No firmware updates or software drivers are required, ensuring operational continuity in regulated or offline environments. For laboratories requiring traceable digital data capture, ATAGO recommends pairing the PAL-91S with its optional RS-232 interface kit (sold separately) and compatible terminal software—enabling timestamped export of measurement logs compliant with FDA 21 CFR Part 11 requirements when deployed within validated GxP frameworks.

Applications

• Routine verification of ethylene glycol concentration in automotive radiator coolant systems prior to winter operation
• Preventive maintenance of chilled water loops in commercial HVAC systems to prevent pipe rupture due to freeze-thaw cycling
• Quality assurance checks during coolant blending operations at distribution centers or OEM service depots
• Field validation of heat transfer fluid integrity in industrial refrigeration units and process cooling circuits
• Educational use in mechanical engineering labs for thermodynamic property correlation studies between concentration, density, and freezing point depression

FAQ

Does the PAL-91S require recalibration before each use?
No—factory calibration remains stable under normal handling and environmental conditions. ATAGO recommends periodic verification using a certified EG standard solution every 30 days or after exposure to extreme thermal shock.
Can it measure propylene glycol concentration?
No—the internal calibration curve is specific to ethylene glycol/water systems. Propylene glycol exhibits different refractive index behavior and requires a dedicated instrument (e.g., PAL-22S).
Is the ATC function adjustable or configurable?
No—the ATC algorithm is fixed and optimized for the 10–100°C operating range; no user input or parameter tuning is available.
What cleaning agents are safe for the prism surface?
Use only distilled water or isopropyl alcohol (≥99%) applied with lens tissue; avoid acetone, chlorinated solvents, or abrasive cloths to preserve prism coating integrity.
How does accuracy vary across the full 0–90% measurement range?
Accuracy is specified per ISO 21748:2017 guidelines—±0.4% (0–15%), ±0.6% (15–22%), ±0.7% (22–55%), and ±0.8% (55–90%)—reflecting increased nonlinearity at higher concentrations due to solution density effects.