ATAGO PAL-91S Ethylene Glycol Refractometer
| Brand | ATAGO |
|---|---|
| Origin | Japan |
| Model | PAL-91S |
| Product Type | Handheld Digital Refractometer |
| Temperature Compensation | Automatic (ATC, 10–100°C) |
| Display | Digital LCD |
| Measurement Range | Ethylene Glycol: 0.0–90.0% (v/v) |
| Freeze Point | 0 to –50 °C |
| Accuracy | ±0.4% (0–15%), ±0.6% (15–22%), ±0.7% (22–55%), ±0.8% (55–90%) for ethylene glycol |
| Resolution | 0.2% (ethylene glycol), 1 °C (freeze point) |
| IP Rating | IP65 |
| Power | Two AAA batteries |
| Dimensions | 5.5 × 3.1 × 10.9 cm |
| Weight | 100 g (instrument only) |
Overview
The ATAGO PAL-91S Ethylene Glycol Refractometer is a compact, handheld optical instrument engineered for rapid, field-deployable quantification of ethylene glycol (EG) concentration in aqueous coolant and antifreeze solutions. It operates on the principle of critical-angle refractometry: incident light undergoes total internal reflection at the prism–sample interface, with the resulting shadow line position directly correlated to the solution’s refractive index. Through built-in calibration algorithms traceable to ATAGO’s proprietary EG refractive index database, the device converts measured refractive index into volumetric percentage (v/v) of ethylene glycol and simultaneously calculates corresponding freeze point temperature (°C) using thermodynamic polynomial models validated against ASTM D1177 and ISO 2982 standards. Designed for operational reliability across ambient conditions, it features automatic temperature compensation (ATC) over a 10–100 °C range, eliminating manual correction and ensuring measurement consistency without external thermostatic control.
Key Features
- Direct dual-parameter readout: simultaneous display of ethylene glycol concentration (0.0–90.0% v/v) and calculated freeze point (0 to –50 °C)
- High-resolution digital LCD with 0.2% resolution for EG concentration and 1 °C resolution for freeze point
- Robust, ergonomic housing rated IP65 for dust and water jet resistance—suitable for workshop, garage, HVAC maintenance, and industrial field use
- Automatic temperature compensation (ATC) eliminates operator-dependent thermal correction and supports measurements across wide process temperature ranges (10–100 °C)
- Lightweight design (100 g) with low-power consumption—powered by two standard AAA batteries with typical service life exceeding 10,000 measurements
- No moving parts or consumables; optical path requires only routine prism cleaning with lens tissue and distilled water
Sample Compatibility & Compliance
The PAL-91S is optimized for homogeneous, non-turbid aqueous ethylene glycol solutions commonly found in automotive engine coolants, chiller brines, HVAC secondary refrigerants, and industrial heat-transfer fluids. It is not intended for glycol blends containing methanol, propylene glycol, or high concentrations of additives (e.g., corrosion inhibitors >5% w/w) that significantly alter refractive index behavior. The instrument complies with JIS K 0061 (Japanese Industrial Standard for refractometers) and meets essential requirements of the EU Measuring Instruments Directive (MID) Annex MI-001 for portable optical density measuring devices. While not certified for GLP/GMP environments per se, its stable calibration, audit-ready measurement repeatability (RSD <0.3% under controlled conditions), and traceable factory calibration support use in quality assurance workflows aligned with ISO/IEC 17025 documentation practices.
Software & Data Management
The PAL-91S is a standalone, embedded-system instrument with no onboard data logging or USB/Bluetooth connectivity. All measurement results are displayed in real time and retained only visually—consistent with its design intent as a rapid verification tool for maintenance technicians and field service engineers. For integration into structured QA/QC systems, users may manually record values into LIMS or CMMS platforms. Calibration verification is performed using ATAGO-certified EG reference standards (e.g., 20%, 50%, and 70% v/v), with optional traceable calibration certificates available upon request. Instrument recalibration is recommended annually or after 5,000 measurements, following ATAGO’s documented procedure (Ref. PAL-91S-CP-2023).
Applications
- Preventive maintenance of automotive cooling systems: verifying EG concentration to ensure freeze protection down to –40 °C in winter climates
- HVAC system commissioning and seasonal servicing: validating chiller brine composition prior to startup and after fluid replacement
- Industrial heat-transfer loop monitoring: periodic checks of glycol-based secondary coolant integrity in food processing, pharmaceutical clean utilities, and semiconductor fab chillers
- Third-party testing laboratories conducting ASTM D3372-compliant antifreeze analysis for supplier qualification
- Educational labs demonstrating colligative property relationships between solute concentration and freezing point depression
FAQ
Does the PAL-91S require user calibration?
No—factory-calibrated at ATAGO’s Tokyo facility using NIST-traceable EG standards; users perform only periodic verification with supplied reference fluids.
Can it measure propylene glycol solutions?
No—the optical algorithm and calibration curve are specific to ethylene glycol/water systems; cross-sensitivity errors exceed ±5% for propylene glycol.
What is the effect of suspended solids or oil contamination?
Turbidity or immiscible phases scatter incident light and invalidate refractive index measurement; samples must be filtered (≤5 µm) and degassed prior to analysis.
Is the instrument suitable for use in explosive atmospheres?
No—it lacks ATEX or IECEx certification; operation is restricted to non-hazardous locations per IEC 60079-0.
How often should the prism surface be cleaned?
After every measurement when used with viscous or residue-forming coolants; use lint-free optical tissue and reagent-grade water—never alcohol or acetone, which may damage the prism coating.
