(EC-800A, EC-825A) Epithelial Voltage Clamps

Single Channel EC-800A and Dual Channel EC-825A
Epithelial voltage clamps from Warner Instruments provide accurate measurements of transepithelial voltage, short circuit current, and membrane resistance. Important features include fluid resistance compensation, membrane resistance readout, choice of voltage compliance, and small watertight preamp headstages. Operating modes include voltage clamp, current clamp, voltmeter, and resistance. The dual channel model includes an internal timer.

The EC-800A and EC-825A are state-of-the-art instruments with several unique and important design features offering more reliable recording and operator convenience.

High CMR
Differential voltage recordings are made with very high common mode rejection providing accurate measurements free from the effects of common mode potential changes of a noisy environment.

Membrane Resistance Measurement Accurate resistance measurements are made with the membrane mounted in the chamber. This measurement is made using a low frequency 2 Hz bipolar signal to avoid polarization of the membrane (ideal for monolayers). Resistances up to 200 kΩ are displayed on the meter with push-button convenience.

Clamp Speed Selection Three clamp speeds provide optimum recording conditions for a variety of applications. In Fast mode, preparations with low access resistance (small tissues or monolayers) can be clamped with speeds as fast as 10µsec. Typical Ussing chambers with larger tissues will use Medium or Slow modes for stable, oscillation free clamping.

Commands
Internal DC Command (Hold) control for both Voltage clamp and Current clamp modes.

Watertight Headstage with Model Membrane
The small compact headstage can be located close to the measurement site to keep input leads short for reduced noise pick-up. The model membrane circuit simulates a preparation to provide convenient operational checks of the clamp. Internal circuits are protected against the invasion of corrosive saline solutions by a watertight seal.

Choice of Voltage Compliance
The EC-800A has a voltage compliance of ±120 V and the EC-825A has a voltage compliance of ±50 V. The high voltage compliance of these instruments are important for studies of low resistance (leaky) epithelial cells and in applications in which long agar leads in the current passing circuit produce large voltage drops (which must be compensated). Additionally, the high compliance helps in charging large membrane capacitances typical of epithelial tissues, resulting in faster settling times and improved overall clamp performance.

External Control
The clamp can be operated by an external programmer, lab timer or computer. Logic control of clamp mode and clamp command levels is possible as well as simultaneous mixing of external linear commands.

Onboard Timer Controller
The dual channel EC-825A includes event timers (2) to provide cycle times and clamp durations up to 2000 seconds. Times are set with 2 digit thumbwheel switches and 4 position range switches. Once set, the timer will free run, eliminating the need for a computer or other external device to control the experiment.