ISOTECH Model 820 Large-Capacity Circulating Bath

Overview

The ISOTECH Model 820 Large-Capacity Circulating Bath is a precision-engineered temperature control system designed for metrological applications in calibration laboratories, quality assurance departments, and R&D facilities. Based on the principle of forced-convection thermal equilibrium, the bath maintains uniform temperature distribution across its 36-liter working volume using a submerged propeller-driven circulation system. This architecture minimizes axial and radial thermal gradients—critical for multi-sensor calibration where spatial uniformity directly impacts measurement traceability. Operating from 30 °C to 200 °C, the unit employs a dual-zone PID-controlled heating system with platinum resistance temperature detectors (PRTDs) mounted at multiple spatial locations to ensure real-time feedback and dynamic thermal compensation. Its stainless-steel tank and corrosion-resistant internal components are compatible with water, silicone oils, and other non-aggressive heat-transfer media commonly used in high-temperature calibration workflows.

Key Features

• 36-liter working volume enables simultaneous immersion of up to twelve 150-mm probe assemblies or six standard mercury-in-glass thermometers per ISO 5725-2 guidelines
• Temperature stability of ±0.01 °C (at setpoint, over 2 hours, measured at geometric center) verified per ASTM E645-20 Annex A1 procedures
• Propeller-driven circulation delivers ≥1.2 L/min flow rate at full load, achieving ≤0.02 °C spatial uniformity across horizontal plane (measured at 9-point grid per EURAMET cg-18)
• Dual independent PRTD sensors—one for control, one for verification—support redundant monitoring and facilitate internal audit trails
• Front-panel interface with calibrated digital display, programmable ramp/soak profiles, and hardware-based over-temperature cutoff (210 °C mechanical limit)
• Stainless-steel construction (AISI 316 tank, AISI 304 housing) ensures long-term dimensional stability and resistance to thermal cycling fatigue

Sample Compatibility & Compliance

The Model 820 accommodates a wide range of temperature-sensitive devices including RTDs, thermistors, liquid-in-glass thermometers, thermocouples (types J, K, T), and infrared reference sources. Its open-bath geometry supports custom fixtures for fixed-point cell handling and ITS-90 realization setups. The system is engineered to support compliance with ISO/IEC 17025:2017 Clause 6.4.3 (environmental monitoring), ASTM E74-22 (force calibration instrumentation), and EURAMET cg-18 (thermometer calibration). When operated with traceable PRTDs and documented SOPs, it meets the requirements for GLP-compliant calibration records under FDA 21 CFR Part 11 when paired with validated data acquisition software.

Software & Data Management

While the Model 820 operates as a standalone instrument, its analog output (0–10 V DC proportional to bath temperature) and RS-232 serial port enable integration with third-party DAQ systems such as LabVIEW, MATLAB, or custom SCADA platforms. Optional ISOTECH BathLink™ software provides time-stamped logging, alarm event capture, and export to CSV or PDF formats compliant with ISO 17025 record retention policies. All logged data includes operator ID, ambient conditions, fluid type, and sensor identification—supporting full auditability during regulatory inspections.

Applications

• Multi-sensor calibration against reference standards in national metrology institutes and accredited calibration labs
• Thermal validation of sterilization cycles and autoclave mapping per ISO 17665-1
• Long-term drift testing of industrial temperature transmitters under controlled thermal stress
• Reference environment for thermometer intercomparison studies organized under CIPM MRA frameworks
• Stabilization platform for optical encoders and laser interferometers requiring sub-millikelvin thermal noise suppression
• Supporting ASTM D341 viscosity-temperature correlation studies using calibrated capillary viscometers

FAQ

What fluid types are recommended for operation at 200 °C?
Silicone oils with flash points >250 °C (e.g., Dow Corning 200 Fluid Series) are recommended. Water is limited to ≤99 °C; glycol-water mixtures are not advised due to oxidative degradation above 120 °C.
Does the Model 820 support external temperature probes for independent verification?
Yes—the bath features a dedicated 4-mm diameter probe port adjacent to the circulation inlet, allowing insertion of a secondary reference PRTD without disrupting thermal uniformity.
Is the unit supplied with calibration documentation?
Each unit ships with a factory-as-tested report including temperature uniformity maps, stability data at three setpoints (50 °C, 100 °C, 150 °C), and traceability to UKAS-accredited standards.
Can the circulation pump be disabled for static bath operation?
No—the propeller system is integral to thermal uniformity; disabling it violates the specified performance envelope and voids metrological validity.
What maintenance intervals are recommended for long-term accuracy?
Annual verification of PRTD calibration and impeller clearance check is advised; fluid replacement frequency depends on usage intensity and thermal history, typically every 18–24 months for silicone oil under continuous operation.