ISOTECH microK² Precision Temperature Bridge
| Brand | ISOTECH |
|---|---|
| Origin | United Kingdom |
| Model | microK² |
| Instrument Type | Precision Temperature Bridge for SPRT, Thermocouples & Thermistors |
| Accuracy | 0.03 ppm (equivalent to 7.5 µK at 273.16 K) |
| Channels | 4-wire resistance measurement with 4 independent measurement channels |
| Display | 10.1-inch capacitive touchscreen (1280 × 800 resolution) |
| Interfaces | Ethernet, dual RS-232, three USB ports |
| Software | ISOTECH BridgeControl™ v3.0 (FDA 21 CFR Part 11 compliant, audit trail enabled) |
| Compliance | Fully supports JJF 2189–2025, ISO/IEC 17025, ASTM E1137/E220, IEC 60751, and ITS-90 traceability requirements |
| Application Domain | Primary and secondary temperature calibration laboratories, national metrology institutes, pharmaceutical QC, aerospace thermal validation |
Overview
The ISOTECH microK² Precision Temperature Bridge is a fourth-generation, high-stability, four-channel resistance bridge engineered for primary-level thermometry and accredited temperature calibration. Based on the proven Wheatstone/Kelvin-Varley topology optimized for cryogenic to high-temperature SPRT (Standard Platinum Resistance Thermometer) measurements, the microK² delivers an unprecedented base accuracy of 0.03 ppm — equivalent to ±7.5 µK at the triple point of water (273.16 K) — while maintaining full compatibility with ITS-90 realization protocols. Designed and manufactured in the United Kingdom, it represents the culmination of over 40 years of dedicated bridge architecture development by ISOTECH’s metrology engineering team — the same group responsible for the ASL F700 series and the Queen’s Award-winning microK platform. Unlike general-purpose digital multimeters or data loggers, the microK² operates as a true null-detecting, current-reversal, low-power excitation bridge system, eliminating self-heating errors and enabling reproducible sub-millikelvin stability over multi-hour calibration cycles.
Key Features
- Four fully independent, auto-balancing measurement channels supporting simultaneous SPRT, PRT, thermistor, and thermocouple (with external reference junction compensation) characterization
- 0.03 ppm base resolution (7.5 µK at 273.16 K), traceable to NPL and NIST through documented uncertainty budgets per ISO/IEC 17025
- 10.1-inch industrial-grade capacitive touchscreen with glove-compatible operation, anti-glare coating, and real-time graphical bridge balance monitoring
- Dual RS-232 ports for legacy probe controllers and dry-well interfaces; Gigabit Ethernet for remote operation and integration into LIMS or MES environments
- Integrated low-noise, programmable current sources (0.1 mA to 1 mA) with automatic range selection and polarity reversal to suppress thermoelectric EMF effects
- Rugged aluminum chassis with thermal mass stabilization, active ambient drift compensation, and internal reference resistor monitoring (10 kΩ, ±0.1 ppm/year stability)
Sample Compatibility & Compliance
The microK² is validated for use with all ITS-90-defined standard sensors: Standard Platinum Resistance Thermometers (SPRTs) from 10 Ω to 2500 Ω nominal, industrial PRTs (Class A/AA per IEC 60751), glass-encapsulated and surface-mount thermistors (NTC/PTC), and base-metal thermocouples (Types T, J, K, E) when paired with certified reference junction modules. It meets the technical requirements of JJF 2189–2025 (“Calibration Specification for Precision Thermometers Used with Platinum Resistance Thermometers”), supports full uncertainty analysis per GUM (JCGM 100), and provides built-in compliance reporting for ISO/IEC 17025 accreditation audits. All firmware and software updates are version-controlled and documented to satisfy GLP and GMP traceability mandates in regulated industries.
Software & Data Management
BridgeControl™ v3.0 is a Windows-based calibration management suite featuring automated ITS-90 fixed-point interpolation (TPW, FPZn, FPAl, etc.), real-time uncertainty propagation, and customizable certificate generation (PDF/A-1b compliant). The software implements full 21 CFR Part 11 functionality — including electronic signatures, role-based access control, immutable audit trails, and secure user authentication — ensuring regulatory readiness for pharmaceutical, medical device, and aerospace applications. Raw resistance data is stored in HDF5 format with embedded metadata (timestamp, environmental conditions, operator ID, sensor ID), enabling seamless import into MATLAB, Python (NumPy/Pandas), or LabVIEW for advanced statistical analysis.
Applications
- Primary calibration of SPRTs against ITS-90 defining fixed points in national metrology institutes (NMIs)
- Secondary calibration of industrial PRTs, thermistors, and thermocouples in accredited calibration laboratories
- Thermal validation of autoclaves, lyophilizers, stability chambers, and environmental test chambers (per ISO 13485, EU Annex 15, and FDA Process Validation Guidance)
- Research-grade thermophysical property measurement in cryogenics, superconductivity, and quantum metrology labs
- On-site field calibration of temperature sensors in nuclear, aerospace, and power generation facilities requiring long-term stability verification
FAQ
What is the maximum allowable lead resistance for 4-wire SPRT measurements on the microK²?
The microK² supports lead resistances up to 50 Ω per wire without degradation in accuracy, thanks to its active lead compensation algorithm and high-input-impedance sensing architecture.
Does the microK² support automated fixed-point cell immersion sequences?
Yes — BridgeControl™ v3.0 includes preconfigured scripts for TPW, FPZn, FPAl, and FPAg cells, with configurable dwell times, ramp rates, and auto-balance thresholds.
Can the microK² be operated remotely via SCPI commands?
Yes — full SCPI command set is implemented over Ethernet and RS-232, enabling integration into automated calibration systems and custom LabVIEW or Python control frameworks.
Is firmware upgrade capability available in the field?
All firmware updates are delivered via signed USB firmware packages with checksum verification and rollback support, ensuring integrity and continuity during metrological operations.
How is traceability maintained across software and hardware revisions?
Each unit ships with a Certificate of Calibration (NIST-traceable), a Firmware Verification Report, and a complete Uncertainty Budget aligned with EURAMET cg-18 and BIPM CCT-K3 guidelines.
