OHAUS Guardian 3000 4×4 Ceramic-Plate Heating Magnetic Stirrer

Overview

The OHAUS Guardian 3000 4×4 Ceramic-Plate Heating Magnetic Stirrer is an engineered solution for laboratories requiring simultaneous precise thermal control and robust mechanical agitation. Built on the principle of magnetic coupling—where a rotating permanent magnet beneath the plate induces rotation in a PTFE- or glass-coated stir bar immersed in the sample—the instrument delivers consistent torque transfer across its full speed range. Its integrated resistive heating element, combined with a high-stability PID temperature controller, enables accurate thermal regulation even in high-heat-capacity media such as silicone oil or glycerol. Designed for extended operation, the system supports uninterrupted stirring at elevated speeds for up to 720 hours—validated under standardized load conditions using aqueous and silicone-oil matrices—making it suitable for long-duration synthesis, dissolution testing, and stability studies where thermal drift and mechanical fatigue are critical failure modes.

Key Features

• Continuous-duty motor architecture rated for 720-hour uninterrupted operation at maximum speed (1600 rpm) with standard load (≤15 L water or equivalent viscosity medium)
• Ceramic-coated heating plate (4×4 inches / 102×102 mm active area) offering chemical resistance, thermal uniformity ±3°C across surface, and rapid heat-up/cool-down kinetics
• Dual-stage thermal safety system: SafetyHeat™ monitors both plate surface temperature and internal chassis temperature via independent sensors; automatic cut-off activates if either exceeds preset thresholds
• High-visibility thermal warning system: LED indicator remains illuminated for ≥30 minutes after power-off when plate surface temperature exceeds 40°C, mitigating accidental contact injury
• Ergonomic interface featuring large backlit LCD display (4-digit speed, 3-digit temperature), tactile rotary encoder for parameter adjustment, and status icons for run/pause, heating active, and error conditions
• Full-metal enclosure with optimized finned heatsink design and IP20-rated ingress protection, ensuring structural integrity, electromagnetic compatibility (EMC), and compliance with IEC 61010-1:2010 safety standards

Sample Compatibility & Compliance

The Guardian 3000 accommodates a broad spectrum of laboratory vessels—including borosilicate glass beakers (50 mL to 5 L), stainless steel reactors, and polypropylene containers—provided they are flat-bottomed and non-magnetic. Stir bar selection (length: 20–80 mm; coating: PTFE, PTFE-glass, or ceramic) is application-dependent and must match fluid viscosity and volume. The unit complies with ISO/IEC 17025:2017 requirements for equipment qualification and supports GLP/GMP workflows through documented calibration traceability (NIST-traceable thermocouple probes available as optional accessories). While not intrinsically safe for flammable solvent environments, it meets CE marking requirements for laboratory electrical equipment (2014/35/EU Low Voltage Directive and 2014/30/EU EMC Directive).

Software & Data Management

This standalone instrument operates without proprietary software or PC connectivity; all parameters are set and monitored locally via the front-panel interface. However, it supports external data logging via optional analog output (0–10 V DC) for speed and temperature signals, compatible with third-party SCADA systems, PLCs, or chart recorders. For regulated environments, users may implement manual logbook entries aligned with FDA 21 CFR Part 11 principles—though electronic audit trails require integration with validated LIMS or ELN platforms. Firmware updates are performed via USB service port (service-mode only) and require OHAUS-certified field engineers.

Applications

• Chemical synthesis requiring homogeneous heating and mixing of viscous reagents (e.g., polymerization initiators in silicone oil baths)
• Pharmaceutical dissolution testing per USP , where precise bath temperature maintenance (±0.2°C) and consistent agitation are mandatory
• Materials science workflows involving nanoparticle dispersion in high-boiling-point solvents (e.g., ethylene glycol, diphenyl ether)
• Environmental analysis sample preparation, including digestion of solid matrices in acid mixtures under controlled reflux conditions
• Biotechnology buffer formulation where thermal-sensitive proteins must remain below denaturation thresholds during pH adjustment and dilution

FAQ

What is the maximum recommended vessel diameter for optimal magnetic coupling on the 4×4 ceramic plate?
For consistent stir bar rotation at ≥1200 rpm, use vessels with bottom diameters ≤90 mm; larger vessels require lower speeds or dual-stir-bar configurations.
Can the unit maintain 500°C setpoint with a 15 L load?
No—500°C is the maximum plate surface temperature under no-load or low-mass conditions (e.g., empty beaker); actual achievable sample temperature depends on vessel material, insulation, and thermal mass.
Is the ceramic plate resistant to hydrofluoric acid (HF) exposure?
No—standard alumina-based ceramic coatings are not HF-resistant; prolonged exposure causes etching and loss of thermal emissivity.
Does the instrument support external temperature probe feedback for closed-loop control?
Yes—when equipped with the optional RTD or thermocouple probe (model-specific), the system switches from plate-sensor to probe-sensor mode for direct sample temperature regulation.
What calibration documentation is supplied with the unit?
Each unit ships with a factory calibration certificate covering speed accuracy (±2 rpm at 1000 rpm) and temperature sensor linearity (±2°C from 50–300°C), traceable to NIST standards.