Hanna HI 8751 & HI 8757 Portable Digital Thermometers

Overview

The Hanna HI 8751 and HI 8757 are handheld digital thermometers engineered for precision, repeatability, and field-ready reliability in academic, industrial, and quality control environments. Unlike traditional liquid-in-glass or bimetallic thermometers—whose accuracy degrades across broad ranges due to thermal expansion nonlinearity—these instruments employ solid-state sensing architectures optimized for metrological integrity. The HI 8751 integrates a factory-calibrated silicon-based resistance temperature detector (RTD) probe (HI765PW), delivering high stability and rapid thermal response (< 5 s to 90% step change) within the –40.0 to +150.0 °C range. In contrast, the HI 8757 utilizes a ruggedized K-type thermocouple probe, enabling extended-range measurements from –50.0 °C up to 1350 °C in two overlapping sub-ranges (–50.0 to +199.9 °C and +200 to +1350 °C). Its onboard microprocessor applies NIST-traceable cold-junction compensation and polynomial linearization per ASTM E230 and IEC 60584-1 standards, ensuring traceable accuracy across extreme thermal gradients.

Key Features

• HI 8751: High-resolution silicon RTD sensor (HI765PW) with 0.1 °C resolution and ±0.2 °C accuracy in the critical biological and refrigeration range (–10.0 to +80.0 °C)
• HI 8757: Dual-range K-type thermocouple interface supporting both low-temperature cryogenic monitoring and high-temperature process validation (e.g., autoclave cycles, furnace calibration, soldering profiles)
• Auto-ranging display with configurable hold function, min/max tracking, and relative (ΔT) mode for differential thermal analysis
• Ruggedized construction: IP65-rated enclosure on HI 8757; impact-resistant ABS housing with stainless steel probe sheath for chemical and mechanical durability
• Low-power design powered by a single 9 V alkaline battery (IEC 6LR61), providing >200 hours of continuous operation under typical lab use
• Factory calibration certificate included; supports user verification via ice-point (0.0 °C) or boiling-point (100.0 °C at sea level) reference checks

Sample Compatibility & Compliance

These thermometers are designed for direct-contact measurement of solids, liquids, gels, and semi-solids where surface or immersion temperature profiling is required. The HI765PW probe (HI 8751) features a 3 mm diameter stainless steel tip and 1 m PVC-insulated cable, suitable for aqueous solutions, food matrices, and ambient air monitoring. The HI 8757’s K-type probe offers interchangeable tip geometries (standard needle, surface contact, and penetration types), compatible with metal surfaces, molten polymers, exhaust gases (with optional protective sheath), and sterilization validation loads. Both models comply with EN 61326-1 for electromagnetic compatibility in laboratory settings and meet CE marking requirements under Directive 2014/30/EU (EMC) and 2011/65/EU (RoHS). Calibration traceability aligns with ISO/IEC 17025–accredited practices when used with NIST-traceable reference standards.

Software & Data Management

While the HI 8751 and HI 8757 operate as standalone instruments without built-in data logging, their analog output capability (HI 8757 only, via optional HI92000 interface cable) enables integration into validated data acquisition systems compliant with FDA 21 CFR Part 11 and EU Annex 11. When connected to Hanna’s HI92000 software suite (Windows-based), users can configure audit trails, electronic signatures, and automated report generation—including timestamped min/max/average values per measurement session. Raw temperature readings retain full resolution during export to CSV or Excel formats, supporting statistical process control (SPC) workflows and GLP/GMP documentation requirements in regulated educational and manufacturing laboratories.

Applications

• Academic teaching labs: Real-time demonstration of thermal equilibrium, phase-change kinetics, and heat transfer coefficients in physics and chemistry curricula
• Food safety QA/QC: Verification of cold chain integrity (refrigerated storage), HACCP critical control point monitoring (cooking/cooling steps), and thermal mapping of blast chillers
• Pharmaceutical manufacturing: Environmental monitoring of stability chambers, lyophilizer shelf temperature validation, and cleanroom HVAC verification
• Maintenance & engineering: Bearing temperature trending in rotating equipment, exhaust gas temperature profiling in combustion systems, and thermal stress testing of electronic assemblies
• Environmental monitoring: Ambient air temperature logging in greenhouse studies, soil temperature profiling in agronomy research, and water column profiling in limnology fieldwork

FAQ

What is the difference between the HI 8751 and HI 8757 in terms of sensor technology and application scope?
The HI 8751 uses a silicon RTD sensor optimized for high accuracy and stability in moderate temperature ranges (–40.0 to +150.0 °C), ideal for life science and food applications. The HI 8757 employs a K-type thermocouple, enabling measurements up to 1350 °C for industrial process and materials testing.
Can the HI 8757 measure below –50 °C?
No—the specified lower limit is –50.0 °C per manufacturer specifications and thermocouple standard tolerances (IEC 60584-1 Class 2). For cryogenic work below –50 °C, consider dedicated low-temperature RTD or thermistor-based instruments.
Is calibration verification possible without external equipment?
Yes—users may perform functional verification using certified ice slurry (0.0 °C) or atmospheric boiling water (100.0 °C at local barometric pressure), provided ambient conditions and probe immersion depth adhere to ASTM E74 and ISO 17025 guidelines.
Does the HI 8751 support data export or PC connectivity?
No—it is a dedicated handheld meter with no serial or USB interface. For data logging capability, consider the HI98501 or HI98509 series, which include RS232 output and bundled software.
Are replacement probes available, and are they calibrated individually?
Yes—Hanna supplies calibrated probe assemblies (e.g., HI765PW for HI 8751; HI8757P for HI 8757), each delivered with individual calibration certificates traceable to NIST standards.