The EVOM™ Manual is WPI's next-generation manual TEER meter, replacing all previously manufactured WPI manual TEER instruments — including the EVOM3, EVOM2, and MilliCell® ERS-2. Engineered for reliability, repeatability, and ease of use, the EVOM™ Manual delivers improved workflow efficiency and more stable measurements for epithelial and endothelial cell culture research.

At its core, the EVOM™ Manual features automatic 20X sample averaging, a low-noise circuit design for greater resolution, and adjustable fixed measurement currents (2, 4, or 10 μA) to suit a wide range of membrane types. Resistance auto-ranging covers 1 Ω to 100,000 Ω across three selectable current ranges, with fast stabilization on low-level readings under 200 Ω to a resolution of 0.1 Ω. The low-current, low-voltage design prevents metal ion transport and is non-destructive to cells and membranes.

Data collection is seamless — the EVOM™ Manual logs measurements continuously to a USB flash drive in CSV format, date-stamped and ready for direct spreadsheet import. A new Windows® companion application provides a secured mode of data transfer in addition to USB storage. The ergonomic tilt stand reduces glare, while automatic plate indexing supports operation with or without control well subtraction for both resistance and potential difference (PD) measurements. Graphical display of popular well plate formats (6, 12, 24, 96) enables trend analysis at a glance. A footswitch enables hands-free recording during experiments.

Key Features

Low-noise design for greater accuracy and resolution in TEER measurement protocols. Automatic 20X sample averaging for improved stability. Adjustable fixed currents: 2, 4, or 10 μA. Resistance auto-ranging from 1 Ω to 100,000 Ω, plus three fixed current ranges. Fast resistance stabilization for readings under 200 Ω, resolution to 0.1 Ω. Continuous USB data logging (PC, Mac, Linux) with date-stamped CSV output. New Windows® companion app for secured data transfer. Graphical display of 6-, 12-, 24-, and 96-well plate formats. Automatic plate indexing with optional control-well subtraction. Footswitch for hands-free recording. Auto-save and data recovery when battery is low. Upgradable firmware. CE certified.

How It Works

Cell monolayer confluence is determined by measuring an increase or plateau in tissue resistance, detected through the EVOM™ Manual's low AC current circuit and the STX4 electrode. The instrument qualitatively assesses monolayer health and quantitatively measures cell confluence. Because it uses low AC current, electrode metal deposits and adverse tissue effects are avoided — unlike DC current approaches. Resistance readings are unaffected by membrane capacitance or voltage, making the system ideal for permeability, PD, and detailed membrane studies.

What is TEER?

TEER (Trans-Epithelial Electrical Resistance) measures the electrical resistance across a cellular monolayer to quantify barrier integrity. High TEER values indicate a tight, intact monolayer with restricted ion permeability. A decreasing TEER signals compromised barrier function. TEER measurement is routinely used to confirm confluent monolayer formation in transwell culture systems before beginning permeability or drug transport studies.

TEER Value Calculation

TEER is a normalized resistance value per unit area (Ω·cm²). To calculate TEER, multiply the measured resistance by the membrane surface area: 6-well plate (24 mm inserts) 4.53 cm², 12-well plate (12 mm inserts) 1.13 cm², 24-well plate (6.5 mm inserts) 0.33 cm², 96-well plate (4.3 mm inserts) 0.145 cm². Example: a 12 mm insert measuring 565 Ω gives a TEER of 565 × 1.13 = 638.5 Ω·cm².

Applications

Blood-brain barrier transport studies. Lung epithelial tissue research. Intestinal tissue permeability assays. Skin barrier studies. Drug permeability and absorption testing. Toxicity and cytotoxicity screening. Continuous digital monitoring of target membranes. Measure epithelial or endothelial tissues for confluence, TEER, and potential difference.

Compatible Electrodes

The EVOM™ Manual is compatible with the STX4 EVOM™ Electrode with Removable Blades (EVM-EL-03-03-01) for 6 mm inserts — the recommended electrode for use with this instrument. Legacy STX2 and STX3 electrodes are supported via the 99672 EVOM Legacy Adapter (sold separately). ENDOHM chambers for endothelial/epithelial measurement are available in 6, 12, and 24 mm insert sizes (EVM-EL-03-01-01 to -03), and include the EVOM™ Manual cable 99916.

What’s Included

EVOM™ Manual Epithelial Volt Ohm Meter (EVM-MT-03-02), 32 GB USB drive (with Python 3.8 program for continuous monitoring), USB cable (503535), 1000 Ω calibration test resistor kit (99673), AC power cord and charger (803025), and foot switch (13142). Note: The 99672 Legacy Electrode Adapter for STX2/STX3 electrodes is sold separately.