The MultiClamp 700B is a computer-controlled microelectrode current and voltage clamp amplifier designed for electrophysiology and electrochemistry. It is a versatile instrument capable of various recording configurations, including single-channel and whole-cell voltage patch clamping, high-speed current clamping (patch or sharp electrode), ion-selective electrode recording, amperometry/voltammetry, and bilayer recording (with an optional headstage).
Function Description:
The MultiClamp 700B operates without front panel knobs and switches, relying instead on the MultiClamp 700B Commander control panel program running on a host computer, communicating via a USB cable. This computer control enables "smart" automatic features such as capacitance compensation, bridge balance, and offsets. Telegraph information, including Gain, Filter, Capacitance, input/output Scaling Factors, and recording Mode, is communicated through software messaging. The Commander interface is independent of acquisition software, making it compatible with various data acquisition packages, including Digidata series digitizers and pCLAMP software (telegraphing supported in pCLAMP versions 9 and higher). An optional SoftPanel device is available for users who prefer hardware control with knobs and buttons.
The device supports one or two primary CV-7 headstages and can accommodate two auxiliary headstages (optional HS- or VG-type). Each CV-7 headstage integrates a current-to-voltage converter for voltage (patch) clamp and a voltage follower for current clamp, allowing convenient switching between low-noise patch-clamp and high-speed current-clamp recording. An optional CV-7 headstage also supports bilayer recording.
Important Technical Specifications:
Main Unit:
- Line Voltage: 85 - 260V AC
- Line Frequency: 50 - 60 Hz
- Fuse: 5 mm x 20 mm, 2A slow
- Case Dimensions: 8.89 cm (3.5") high x 48.26 cm (19") x 30.48 cm (12") deep, rack mountable.
CV-7 Headstage:
- Dimensions: 4.06 x 8.38 x 2.03 cm (1.6" x 3.3" x 0.8")
Voltage Clamp:
- Gain (Feedback Resistor, R_f): 50 GΩ, 5 GΩ, 500 MΩ, 50 MΩ
- 10 kHz Noise (8-pole Bessel filter):
- 50 GΩ: 0.28 pArms
- 5 GΩ: 0.9 pArms
- 500 MΩ: 1.4 pArms
- 50 MΩ: 3.0 pArms
- 5 kHz Noise (4-pole Butterworth filter):
- 50 GΩ: 0.15 pArms
- 5 GΩ: 0.5 pArms
- 500 MΩ: 0.8 pArms
- 50 MΩ: 2.0 pArms
- Fast Capacitance Compensation Magnitude:
- 0 - 12 pF for 50 GΩ range
- 0 - 36 pF on all other ranges
- Fast Capacitance Compensation Tau: 0.5 µs to 1.8 µs
- Slow Capacitance Compensation Magnitude:
- 0 - 1 pF for 50 GΩ range
- 0 - 3 pF on all other ranges
- Slow Capacitance Compensation Tau: 10 µs to 10 ms (in two ranges: 10 – 200 µs and 200 – 4000 µs)
- Whole Cell Capacitance Compensation:
- C_m from 1 pF to 100 pF and R_s from 400 kΩ to 1000 MΩ on 500 MΩ range.
- C_m from 2.5 pF to 1000 pF and R_s from 100 kΩ to 100 MΩ on 50 MΩ range.
- Series Resistance Compensation:
- Bandwidth adjustable from 0.32 to 16 kHz.
- Series resistances corrected: 0.4 to 1000 MΩ on 500 MΩ range; 0.1 to 100 MΩ on 50 MΩ range.
Current Clamp:
- Rise Time:
- < 10 µs for load of 10 MΩ on 50 MΩ range (Output Filter bypassed).
- < 30 µs for load of 100 MΩ on 500 MΩ range.
- < 150 µs for load of 1 GΩ on 5 GΩ range.
Test Signals:
- Voltage Clamp: Seal Test, Pulse, Zap. Amplitudes selectable from 0 to ±1 V. Seal Test frequency 2 to 1000 Hz. Pulse duration 0.1 to 500 ms. Zap fixed at +1V with 0.1 to 50 ms duration.
- Current Clamp: Tune, Pulse, Buzz, Clear (+/-). Tune and Pulse amplitudes 0 to ±10 V/R_f amps. Tune frequency 2 to 1000 Hz. Pulse duration 0.1 to 500 ms. Buzz amplitude fixed at ±15 V signal with 0.05 to 500 ms duration. Clear (+/-) amplitude fixed at ±15 V signal.
DC Holding Commands:
- Voltage Clamp: ±1000 mV range in 30 µV steps. Auto Pipette Offset adjusts DC holding potential to zero Membrane Current.
- Current Clamp: ±20 nA range in 0.7 pA steps (50 MΩ range); ±2 nA range in 0.07 pA steps (500 MΩ range); ±0.2 nA range in 0.007 pA steps (5 GΩ range). Auto Pipette Offset adjusts DC holding current to zero Membrane Potential.
Output Gain and Filters:
- Primary Output Gain: 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000.
- Secondary Output Gain: 1, 2, 5, 10, 20, 50, 100.
- Primary Output Filters: Lowpass 4-pole Bessel/Butterworth (various frequencies), Highpass single-pole Bessel (DC, 0.1, 1, 3, 10, 30, 100, 300 Hz).
- Secondary Output Filters: Lowpass single-pole Bessel fixed at 10 kHz or Bypass.
- Scope Filter: Lowpass two-pole Bessel with 1k, 3k, 10k Hz cutoff frequencies or Bypass.
- Sensitivity: 20 mV/V or 100 mV/V for V-Clamp; 400 pA/V or 2 nA/V for I-Clamp.
- Input Impedance: 10 kΩ.
Mode Switching:
- External: 0 V input to MODE BNC selects I-Clamp, 5 V selects V-Clamp.
- Internal Auto Mode Switching: Automated switch from I-Clamp to V-Clamp on Vm threshold crossing (Positive to Negative or Negative to Positive, ±1000 mV threshold). Delay to switch (0-500 ms), Delay to return from V-Clamp (20ms – 500 seconds).
- Switching Speeds: Auto I-Clamp to V-Clamp < 0.5 ms; Auto V-Clamp to I-Clamp ≈ 22 ms. Manual switching adds ~30 msec delay.
Audio Monitor:
- Selectable output: Current, Voltage, or Voltage x 100 for Channel 1 or 2.
- Modes: Direct Signal Monitoring or Voltage Controlled Oscillator (VCO).
- VCO Range: ~4000 Hz @ +100 mV to ~300 Hz at –100 mV.
Usage Features:
- Glider Control: Parameters can be adjusted by positioning the cursor over a field and dragging the mouse. Shift and Ctrl keys magnify the effect. Dual controls allow simultaneous adjustment of two parameters (e.g., capacitance and time constant).
- Direct Text Entry: Parameters can be set by double-clicking a field, typing a number, and pressing Enter.
- List Selection: Some parameters (e.g., frequency, output signals) can be selected from a list by right-clicking.
- Quick Select Buttons: Allow users to store and rapidly retrieve parameter settings or run executable command lines, useful for different experimental configurations or shared setups.
- Pipette Offset: Automatically zeros the membrane current in V-Clamp or membrane potential in I-Clamp.
- Seal Test/Tuning: Applies repetitive pulses to measure electrode resistance and monitor seal formation or membrane potential.
- Capacitance Compensation (Cp Fast/Slow, Whole Cell): Electronically compensates for electrode and cell capacitance transients to prevent amplifier saturation and signal distortion. Auto buttons assist in finding optimal compensation values.
- Leak Subtraction: Subtracts linear leak currents from the membrane current in V-Clamp mode, useful for single-channel recordings.
- Bridge Balance: Compensates for voltage drops across the microelectrode in I-Clamp mode, ensuring only the true membrane potential is recorded. Auto Bridge Balance button for automatic adjustment.
- Buzz: Applies a brief, high-frequency square wave to aid cell impalement or clear blocked electrode tips.
- Zap: Delivers a large, brief voltage pulse (1 V DC) to rupture the patch for whole-cell recording, with selectable durations.
- Pulse Button: Allows application of simple, on-off voltage or current steps with selectable amplitude and duration.
- Automatic Mode Switching: Automates switching between I-Clamp and V-Clamp based on membrane potential thresholds and delays, useful for dynamic experimental protocols.
- External Command Inputs: Accepts complex stimulus protocols from external pulse generators or computer programs via BNC connectors.
- Command Filter Frequency: Low-pass filters command stimuli to smooth sharp transitions and prevent capacitance transient saturation.
- Output Zero: Subtracts a constant DC offset from the Primary Output signal.
Maintenance Features:
- Fuse Replacement: The manual provides instructions for safely changing the 2A slow fuse in case of failure, emphasizing investigation of the cause before replacement.
- Headstage Cleaning: The headstage connector should be wiped with a damp cloth to clean salt spills. Liquids should be avoided. The Teflon input connector should be kept very clean, using alcohol or deionized water for effective cleaning.
- Holder Maintenance:
- Cleaning: Holders should be frequently rinsed with distilled water, or mildly soapy water/ethanol for thorough cleaning. Methanol or strong solvents should be avoided.
- Silver Wire Replacement: Instructions are provided for inserting and bending the silver wire into the silicone seal and securing it with the threaded collar.
- Holder Design: Made of polycarbonate for low noise, with different barrel lengths for various recording needs. Uses cone washers for secure pipette insertion.
- Static Precautions: Users are advised to touch a grounded metal object before handling the headstage in environments with high static electricity.
- Shipping: Detailed instructions are provided for proper packaging of the MultiClamp 700B for shipping, recommending original factory cartons or robust foam/bubble-pack wrapping to prevent damage.
The MultiClamp 700B is designed for laboratory use and is NOT INTENDED FOR HUMAN EXPERIMENTATION OR APPLICATION TO HUMANS IN ANY WAY. Operation in a manner not specified by the manufacturer may impair the protection provided by the equipment. It should be used indoors in a clean, dry environment, with mains supply fluctuations not exceeding ±10% of nominal voltage, at temperatures between 5 °C and 40 °C, and at altitudes up to 2000 m. Headstages should only be connected or disconnected when the amplifier is turned off.
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