Electrocardiograph tester CMRR 3.0E

electrical safetyintegritysignal

Overview
CMRR 3.0E is a product designed to perform EEG common-mode rejection ratio tests in accordance with IEC 80601-2-26:2019 and Chinese regulation GB 9706.226. The unit integrates multiple circuit designs and internal/external shielding to reduce test complexity and environmental noise. CMRR 3.0E delivers reproducible test data for R&D, compliance verification and production-line testing of medical EEG equipment.

Origins
Medical monitoring equipment operates in electrically noisy environments. The common-mode rejection ratio (CMRR) test verifies whether the device under test (DUT) suppresses common-mode interference to preserve signal integrity and diagnostic accuracy. CMRR 3.0E uses double-layer circuit shielding and a dedicated external shielding mechanism to isolate ambient interference. An optional external shielding cover is available for higher-precision measurements. The instrument increases measurable CMRR (up to 120 dB, exceeding the 89 dB requirement) and adopts an 11:1 (110 MΩ : 10 MΩ) voltage divider and measurement circuit to automatically determine the common-mode point voltage Vc after the 100 pF capacitor, addressing practical measurement challenges. A built-in sine-wave generator provides standard test voltages and frequencies (including 20, 2.828, 0.5 Vrms and 2 Vrms). An SDK enables automated test development and a Standard Assistant Software (sold separately) guides compliance test setup and execution.

Features

• Built-in calibrated sine-wave generator and voltage measurement circuit to ensure test signal accuracy and monitor common-mode point voltage.
• Multi-circuit design with MCU and electronic relays for manual or automated switching of RC lines and voltage options.
• Double-layer shielding (internal circuit shielding plus external mechanism) to isolate environmental noise effectively.
• Wide voltage testing range: supports standard values 0.5 / 2.828 / 20 / 2 Vrms and extends up to 70.71 Vrms.
• Touchscreen interface for electrode selection and impedance superposition; variable capacitor adjustment for fine tuning.
• Automated testing via SDK for software-controlled test sequences.
• Standard Assistant Software (sold separately) to assist configuration and execution of compliance tests.

Highlights

• All-in-one circuit design overcomes common testing limitations; built-in calibrated generator compensates for insufficient output of general signal generators.
• Calibrated voltage measurement circuit confirms the common-mode point voltage when adjusting variable capacitance.
• High CMRR in unbalanced tests up to 111 dB; optional shielding cover enables even higher CMRR measurements.
• Simplified test procedure allowing completion of standard-required items with minimal user intervention.

Ordering / Package Contents (example system)

• Model No.: CMRR 3.0E
• EEG CMRR tester with 11 compound terminals for IEC 80601-2-26:2019 and GB 9706.226
• Package contents: CMRR 3.0E x 1; Top shielding cover x 1; Bottom shielding cover x 1; Compound terminal x 11; USB cable x 1; Grounding wire x 1; 12V Power adapter x 1 (power cord excluded)

Technical specifications

• Supply voltage: 0.5 / 2.828 / 20 / 2 / (70.71) Vrms — ±1%*
• CM point voltage: 1.414 / 10 / 1 / (35.355) Vrms — ±1% (0.25 Vrms ±2%)
• Frequency: 50 / 60 / 100 / 120 Hz — ±1%
• Electrode with Impedance: change electrode via the touch screen — Options: None / RA / LA / LL / V1 / V2 / V3 / V4 / V5 / V6 / ALL
• Electrode without Impedance: change electrode via the touch screen — Options: RA / LA / LL / V1 / V2 / V3 / V4 / V5 / V6
• Imbalance impedance, R: 10 kΩ — 10 kΩ ±1%
• Imbalance impedance, C: 47 nF — 47 nF ±5%
• DC offset: Powered by a replaceable preinstalled battery, can be added on RA / LA / LL / V1~V6 — 150 mV ±1%; Up to 40 hrs with intermittent use
• 100 pF capacitor: measured indirectly using 11:1 (110 MΩ : 10 MΩ) voltage divider — 100 pF ±5%
• Environment: Intended for normal laboratory environment; stable selection of critical components in the stated range. Note: the 110 MΩ divider may be affected by high humidity in excess of 85% — Operating: 15 - 30°C; 10 - 75% RH
• *Measurement note: require measurement with a multimeter of higher accuracy.