NPI TEC-B-01 Operating instructions

OPERATING INSTRUCTIONS AND
SYSTEM DESCRIPTION FOR THE
TEC-B-01
VOLTAGE CLAMP UNIT FOR BRIDGE
AMPLIFIERS
VERSION 1.1
npi 2014
npi electronic GmbH, Bauhofring 16, D-71732 Tamm, Germany
Phone [phone]; Fax: [phone]
[email protected]; http://www.npielectronic.com

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Table of Contents
1.Safety Regulations...............................................................................................................3
2.TEC-B-01 ............................................................................................................................4
2.1.Components .................................................................................................................4
2.2.System Description ......................................................................................................4
2.3.Description of the Front Panel .....................................................................................4
Current Headstage Bias Current Adjustment for TEC-B-01 .......................................7
Tuning procedure:........................................................................................................7
2.4.Description of the Rear Panel ......................................................................................9
3.Operation.............................................................................................................................9
3.1.Stand Alone Operation.................................................................................................9
3.2.Operation with Bridge Amplifier.................................................................................10
Voltage clamp: .............................................................................................................10
Current clamp:..............................................................................................................10
3.3.BUZZ or Penetration mode..........................................................................................10
4.Simple cell model................................................................................................................11
4.1.Cell Model Description................................................................................................11
4.2.Basic settings ...............................................................................................................12
4.3.Connections and Operation..........................................................................................13
Checking the Configuration with the Cell Model........................................................13
5.Test and Tuning Procedures................................................................................................13
5.1.Current Headstage Bias Current Adjustment...............................................................13
5.2.Offset Compensation....................................................................................................15
Potential Electrode .......................................................................................................15
Current Electrode .........................................................................................................15
5.3.Electrode Resistance Test ............................................................................................15
Potential Electrode (BA-03X)......................................................................................16
Current Electrode (TEC-B-01).....................................................................................16
5.4.Capacity Compensation ...............................................................................................16
5.5.Testing Operation Modes.............................................................................................17
Current Clamp..............................................................................................................17
Voltage Clamp .............................................................................................................17
5.6.Tuning the VC mode....................................................................................................18
General Considerations ................................................................................................ 19
Tuning Procedure.........................................................................................................20
6.Positioning of Electrodes ....................................................................................................22
7.Sample Experiment .............................................................................................................23
8.Trouble Shooting.................................................................................................................25
9.Appendix .............................................................................................................................26
9.1.Theory of Operation.....................................................................................................26
9.2.Tuning Procedures for VC Controllers ........................................................................28
Practical Implications...................................................................................................28
9.3.Speed of Response and Linearity of the Capacitive Transients...................................31
10.Technical Data .............................................................................................................34

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1. Safety Regulations
VERY IMPORTANT:Instruments and components supplied by npi electronic are NOT
intended for clinical use or medical purposes (e.g. for diagnosis or treatment of humans), or for
any other life-supporting system. npi electronic disclaims any warranties for such purpose.
Equipment supplied by npi electronic must be operated only by selected, trained and adequately
instructed personnel. For details please consult the GENERAL TERMS OF DELIVERY AND
CONDITIONS OF BUSINESS of npi electronic, D-71732 Tamm, Germany.
1) GENERAL: This system is designed for use in scientific laboratories and must be operated only
by trained staff. General safety regulations for operating electrical devices should be followed.
2) AC MAINS CONNECTION: While working with npi systems, always adhere to the appropriate
safety measures for handling electronic devices. Before using any device please read manuals and
instructions carefully.
The device is to be operated only at 115/230 Volt 60/50 Hz AC. Please check for appropriate line
voltage before connecting any system to mains.
Always use a three-wire line cord and a mains power-plug with a protection contact connected to
ground (protective earth).
Before opening the cabinet, unplug the instrument.
Unplug the instrument when replacing the fuse or changing line voltage. Replace fuse only with
an appropriate specified type.
3) STATIC ELECTRICITY: Electronic equipment is sensitive to static discharges. Some devices
such as sensor inputs are equipped with very sensitive FET amplifiers, which can be damaged by
electrostatic charge and must therefore be handled with care. Electrostatic discharge can be
avoided by touching a grounded metal surface when changing or adjusting sensors. Always turn
power off when adding or removing modules, connecting or disconnecting sensors,
headstages or other components from the instrument or 19” cabinet.
4) TEMPERATURE DRIFT / WARM-UP TIME: All analog electronic systems are sensitive to
temperature changes. Therefore, all electronic instruments containing analog circuits should be
used only in a warmed-up condition (i.e. after internal temperature has reached steady-state
values). In most cases a warm-up period of 20-30 minutes is sufficient.
5) HANDLING: Please protect the device from moisture, heat, radiation and corrosive chemicals.

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2. TEC-B-01
2.1. Components
The following items are shipped with the TEC-B-01 system:
TEC-B-01 amplifier
Headstage
Ground connector for headstage (2.6 mm)
Power cord
User manual
Optional accessories:
Electrode holder
Electrode holder adapter for mounting to a micromanipulator
Passive cell model
2.2. System Description
The TEC-B-01 amplifier module is designed to be used together with a modified BA-1S, BA-01X or
BA-03X bridge amplifier. In two-electrode CC or VC mode the current is applied through the current
electrode connected to the TEC-B-01 and potential measurement is performed through the bridge
amplifier. The active connection of the two amplifiers is indicated by the DUAL LED. The bridge
amplifier has also an LED besides the display indicating two-electrode operation.
It is also possible to use the bridge amplifier as usual only with the electrode connected the BA-1S,
BA-01X or BA-03X. For operation of the bridge amplifier using only one electrode, the MODE OF
OPERATION switch of the TEC-B-01 has to be set into EXT or OFF position. In EXT position the
TEC-B-01 can be used as current pump, e.g. for iontophoresis.
2.3. Description of the Front Panel
In the following description of the front panel elements each element has a number that is related to
that in Figure 1. The number is followed by the name (in uppercase letters) written on the front panel
and the type of the element (in lowercase letters). Then, a short description of the element is given.

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Figure 1: front panel view of the TEC-B-01

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(1) MODE OF OPERATION switch
Switch to select the MODE OF OPERATION:
VC: Voltage Clamp
OFF: In this position the current injection of the amplifier is switched OFF, e.g. for
operating the bridge amplifier as stand-alone device
CC: Current Clamp with current injection through the current headstage
Note: In CC operation the current stimulus input of the bridge amplifier is used!
EXT.: EXTernal control. For operating the TEC-B-01 amplifier as a constant current
source, e.g. for iontophoresis, or for operating the bridge amplifier as stand-alone
device
POWER OFF: Power is turned OFF
(2) GAIN VC potentiometer
10-turn potentiometer to set amplification factor (GAIN) of the VC error signal. To keep the VC error
as small as possible it is necessary to use high GAIN settings, but the system becomes unstable and
begins to oscillate if the GAIN is set too high.
(3) Rs COMP. potentiometer
10-turn potentiometer to set the amount of series resistance compensation. Series resistance
compensation improves the performance of the clamp system, especially if fast voltage-activated
currents are recorded.
Important: Series resistance compensation is done by positive feedback in the control circuit, which
can lead very quickly to stability problems. Therefore, tuning of the series resistance compensation has
to be carried out with great care!
(4) CURRENT FILTER (Hz) switch
6-position switch to set the corner frequency of the CURRENT FILTER (100, 300, 500, 1k, 3k or
5k Hz) available at #17.
(5) CUR. OUTP. SENS. (V/µA) switch
Switch to set the amplification of the current signal at #17 (0.1 V/µA, 1 V/µA, 10 V/µA).
(6) HOLDING POTENTIAL potentiometer
10-turn potentiometer for setting the HOLDING POTENTIAL in VC mode
(7) + /0 /- switch
Switch for setting the polarity of the HOLDING POTENTIAL in VC mode. In 0 position the
HOLDING POTENTIAL is disabled, i.e. set to 0 mV.
(8) DUAL LED
LED indicating operation with a bridge amplifier in CC or VC mode.

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(9) Display
LED display for the CURRENT passed through the CURRENT electrode in µA (XX.XX µA, switch
#10 in ICEL position) or the potential at the current electrode in mV (XXXX mV, switch #10 in VCEL
position) or the resistance of the current electrode (XX.X M, switch #10 in RCEL position).
(10) VCEL / ICEL / RCEL / switch
3-position switch for selection of the display mode:
VCEL: potential of the current electrode is displayed
ICEL: current value is displayed
RCEL: resistance of the current electrode is displayed
(11) OFFSET potentiometer
10-turn potentiometer to cancel potential OFFSETs at the current electrode.
(12) BIAS CEL trim pot.
Trim pot for adjusting the current headstage BIAS current.
Current Headstage Bias Current Adjustment for TEC-B-01
Caution: It is important that this tuning procedure is performed ONLY after a warm-up period of at
least 30 minutes!
The tuning procedure should be performed regularly (at least once a month) with great care since the
bias current changes over time and it determines the accuracy of the TEC-BA system.
The TEC-B-01 is equipped with a current source that is connected to the current injecting electrode
and performs the current injection. This current source has a high-impedance floating output.
Therefore, the zero point (the zero of the BIAS current) of the current source must be defined, i.e.
without an input signal there should not be an output current.
The tuning procedure is done using the BIAS CEL trim pot and one resistance of a few kand one of a
few M. It is based on Ohm's Law (U = R * I).
If the headstage generates an output current, this current will cause a voltage deflection at a test
resistor. If this test resistor has a low resistance of only a few k, this voltage deflection originates
only from a possible offset of the electrode, that can be cancelled using the OFFSET CEL (#11, Figure
1) potentiometer.
Replacing the low resistance resistor by one of a much higher resistance may lead to another voltage
reading at the digital display. This voltage deflection then originates only from the BIAS output
current and is proportional to this output current according to Ohm’s law. Using the BIAS CEL trim
pot. the monitored voltage can be set to 0. This cancels the BIAS current.
Tuning procedure:
The tuning procedure is performed using high-value resistors. It cannot be performed with an
electrode, since there are always unknown potentials involved (tip potential, junction potentials etc.).
Warning: High voltage! Always turn power off when working directly on the current headstage
output.


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Set the MODE OF OPERATION switch to OFF.
Important: The tuning procedure must not be done in VC mode!!
Connect the electrode connector of the TEC-B-01 headstage to ground. If parasitic oscillations
occur use a 10 kresistor for grounding.
Switch the digital display (#9) to VCEL (potential output of the current electrode) using switch #10.
Set the reading of the display to 0 using the OFFSET potentiometer (#11).
After tuning the current electrode potential OFFSET simulate an electrode by replacing the 10 k
resistor with a much larger resistor (e.g. 1 M).
The digital display (and the CURRENT ELECTRODE potential connector (CEL x10mV) (#18))
now shows a voltage deflection that is related to the BIAS current of the headstage according to
Ohm's Law. Cancel this voltage by tuning the BIAS CEL trim pot (#12). The current is 0 if the
voltage deflection is 0.
Note: Due to the characteristics of the high voltage OpAmps the VCEL display may fluctuate around the
baseline of 0 mV by some mV. With a 1 Mresistor (as used in the cell model) 1 mV corresponds to
1 nA. Keeping in mind that the display accuracy of the current is 10 nA in the last digit this is
insignificant.
Important: The bridge amplifier it has a BIAS current as well and must be adjusted as described in the
bridge amplifier user manual.
(13) CAP.COMP. potentiometer
Control for the capacity compensation of the CURRENT electrode or the signal connected to the EXT
IN connector #16 (potentiometer with OFF position, clockwise).
Note: For experiments with oocytes, it is recommended to switch the CAP.COMP potentiometer to
OFF position.
Important: If the CAP. COMP is switched off, the BUZZ function for the CEL is also disabled.
(14) Current HEADSTAGE connector
Connector for the current headstage.
(15) COMMAND IN ÷10 mV connector
BNC connector for an external COMMAND voltage in VC mode (sensitivity: ÷10 mV). The signal
form remains unchanged.
(16) EXT IN 1 µA/V connector
BNC connector for connecting an external voltage signal. This can be used to operate the TEC-B-01
module as a constant current source, e.g. for iontophoresis. Scaling is 1 µA / V, i.e. 100 mV connected
at EXT IN leads to a current of 100 nA at the current electrode.
(17) CURRENT OUT connector
BNC connector providing the current signal. The scaling is set by switch #5. The filter is set by switch
#4.

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(18) CEL x10 mV connector
BNC connector providing the potential of the current electrode.
(19) ms INTEGRATION potentiometer
The integrator improves control performance for slower signals. Position OFF disables the integrator.
Setting a time constant by turning the potentiometer clockwise converts the controller into a PI
(proportional-integral) system. Time constant range is 10…0.1 ms.
2.4. Description of the Rear Panel
A cable is firmly connected for linking the TEC-B-01 amplifier to the bridge amplifier connector TO
TEC-B-01 at the rear panel of the bridge amplifier.
CHASSIS
This connector is linked to mains ground (green / yellow wire, protective earth).
GROUND
This connector is linked to the internal system ground which has no connection to the 19" cabinet
(CHASSIS) and the mains ground to avoid ground loops.
3. Operation
The TEC-B-01 can be operated as a stand-alone device or in conjunction with a modified bridge
amplifier.
3.1. Stand Alone Operation
The TEC-B-01 can be used as a current pump, e.g. for iontophoresis. The MODE OF OPERATION
switch (#1, Figure 1). A voltage signal is connected to the EXT IN BNC connector (#16, Figure 1).
This voltage signal is converted into a current signal with a scaling of 1 µA / V. The (mostly
rectangular) shape of the input signal can be influenced by the capacity compensation.

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3.2. Operation with Bridge Amplifier
Figure 2: front panel of BA-03X
Together with a modified bridge amplifier the TEC-B-01 can be used for two electrode voltage clamp
(TEVC) or two electrode current clamp (TECC) experiments. The scaling is adapted for current ranges
normally used in experiments with oocytes.
Figure 3: Rear panel connector of the BA-03X for connection with TEC-B-01 (left). A DUAL LED on
the front panel of the BA-03X indicates two electrode operation (right).
For two electrode operation the TEC-B-01 and bridge amplifier are connected with a cable at the rear
panel. The operation mode switch (#1) is set to CC (for current clamp) or VC (for voltage clamp). The
current electrode is connected to the TEC-B-01 headstage and the potential electrode to the headstage
of the bridge amplifier.
In two electrode operation current injection is done with the current electrode (connected to the TEC-
B-01) and potential measurement with the potential electrode (connected to the bridge amplifier. This
applies to both CC and VC mode.
Two electrode operation is indicated by the DUAL LED at the TEC-01-B as well as by the DUAL
LED at the bridge amplifier. Current display and current output at the bridge amplifier are disabled.
Voltage clamp:
In voltage clamp mode, the command signal is fed into the COMMAND IN BNC connector (#15) at
the TEC-B-01 front panel.
Current clamp:
In current clamp mode, the command signal is fed into one of the STIMULUS INPU BNC connectors
(#23 or #24) at the BA-03X front panel.
3.3. BUZZ or Penetration mode
In two electrode configuration, the BUZZ module of the BA-03X works for both the
potential electrode from BA-03X (PEL) and the current electrode from TEC-B-01 (CEL).
The BUZZ select switch at the BA-03X front panel allows selection which electrode the
BUZZ shall be applied to.

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4. Simple cell model
4.1. Cell Model Description
Figure 4: TEC passive cell model
PEL BNC: connector for the potential electrode, resistance: 1 M
REF SUBCLICK: subclick (SMB) connector for the reference electrode (optional)
GND: ground connector
RM: switch for the cell membrane representing a membrane resistance of either 10 k
or 100 k
CM: cell membrane capacity, always 100 nF
ON / GND: switch to ground the current electrode, ON = CEL inside the cell, GND = CEL
connected to ground (see also chapter 0)
CEL SUBCLICK: SMC connector for the current electrode, resistance: 1 M
(built as BNC connector for TEC-B-01).

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Figure 5: schematic diagram of the TEC passive cell model. For TEC-B-01, there is no REF connector
and Rbath = 0 Ω.
4.2. Basic settings
Before using the TEC-B-01 always make the basic settings to avoid oscillations.
Basic settings
Turn all controls to low values (less than 1) and each symmetrical offset adjustment, i.e. C.
HEADSTAGE BIAS CURRENT, CURRENT ELECTRODE OFFSET and POTENTIAL
OFFSET potentiometers, in the range of 5 (zero position, see chapter 2.2). Set the CAPACITY
COMPENSATION (#13) to OFF.
Disable the HOLD unit by setting the + / 0 / - switch (#7) to 0.
Set the MODE OF OPERATION (#1) to CC.
Set the display to POTENTIAL ELECTRODE using switch #10.
Now the TEC-B-01 is ready for an initial check with the cell model.

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4.3. Connections and Operation
Checking the Configuration with the Cell Model
Make the basic settings (see chapter 4.2).
Connect the PEL BNC jack of the cell model to the BNC connector at the potential headstage.
Connect the BNC jack CEL to the connector at the current headstage.
Switch the CELL membrane switch (see Figure 4) to the desired position.
Set the GND switch (see Figure 4) to ON.
Turn POWER switch of the amplifier on.
Now you can adjust the amplifier and apply test pulses to the cell model. Connection to both BNC
connectors gives access to the cell via a potential and current electrode with 1 Mresistance. In the
upper position, the RMswitch simulates a cell membrane with a resistance of 10 k. In the lower
position, a cell membrane with 100 kis simulated. The membrane capacity is always 100 nF (see
also chapter 5.5).
5. Test and Tuning Procedures
Important: The TEC-B-01 and BA amplifiers should be used only in warmed-up condition, i.e. 20 to
30 minutes after turning power on.
The following test and tuning procedures are necessary for optimal recordings. It is recommended first
to connect a cell model to the amplifier to perform some basic adjustments and to get familiar with
these procedures.
5.1. Current Headstage Bias Current Adjustment
Caution: It is important that this tuning procedure is performed ONLY after a warm-up period of at
least 30 minutes!
The tuning procedure must be performed regularly (at least once a month) with great care since the
bias current changes over time and it determines the accuracy of the TEC system.
The TEC-03X is equipped with a high-voltage current source that is connected to the current injecting
electrode and performs the current injection. This current source has a high-impedance floating output.
Therefore, the zero point (the zero of the bias current) of the current source must be defined, i.e.
without an input signal there should not be an output current.
Since the high-voltage FET amplifiers that are used become warm from the internal heat dissipation
and their characteristics are strongly temperature dependent, the calibration procedure has to be done
periodically by the user.
The tuning procedure is done using the C. HEADSTAGE BIAS CURRENT control and one resistance
of a few kand one of a few Mor a cell model. It is based on Ohm's Law
(U = R * I).

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If the headstage generates an output current, this current will cause a voltage deflection at a test
resistor. If this test resistor has a low resistance of only a few kthis voltage deflection is nearly zero,
and a possible reading at the digital display originates only from a possible offset of the electrode,
which can be cancelled using the (CURRENT ELECTRODE) OFFSET (#11) potentiometer.
Replacing the low resistance resistor by one of a much higher resistance may lead to another voltage
reading at the digital display. This voltage deflection then originates only from the BIAS output
current and is proportional to this output current according to Ohm’s law. Using the BIAS CEL (#12)
control the monitored voltage can be set to 0.
The tuning procedure is performed using high-value resistors or a cell model. It cannot be performed
with an electrode, since there are always unknown potentials involved (tip potential, junction
potentials etc.).
Warning: High voltage! Always turn power off when working directly on the current headstage
output.
Put the holding current switch to position 0 (+ / 0 / - switch, #7). If you use a cell model, only the
CEL and GND connectors must be connected.
Set the MODE OF OPERATION switch to OFF.
Important: The tuning procedure must not be done in VC mode!!
Connect the CURR.EL connector of the current headstage to ground. If parasitic oscillations occur
use a 10 kresistor for grounding. If you use a cell model set the ON / GND switch to GND.
Switch the digital display (#9) to VCEL (potential output of the current electrode) using the
electrode selector (#10). Set the reading of the display to 0 using the potentiometer OFFSET (#11).
After tuning the current electrode potential OFFSET connect the cell model (see chapter 4.2). If
you do not use a cell model simulate an electrode by replacing the 10 kresistor with a much
larger resistor (min. 5-10 M).
The digital display (and the CURRENT ELECTRODE potential connector (CEL x10mV (#18))
now shows a voltage deflection that is related to the BIAS current of the headstage according to
Ohm's Law. Cancel this voltage by tuning the headstage BIAS CEL potentiometer (#12). The
current is 0 if the voltage deflection is 0.
Now the CURRENT OUTPUT (#17) and the CURRENT DISPLAY (#9) should also read 0.

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5.2. Offset Compensation
If an electrode is immersed into the bath solution an offset voltage will appear, even if no current is
passed. This offset potential is the sum of various effects at the tip of the electrode filled with
electrolyte (“tip potential”, junction potential etc.). This offset voltage must be compensated i.e. set to
0 carefully with the OFFSET controls (#11 at TEC-01B and #16 at BA-03X) before recording from a
cell. The OFFSET compensation is done in CC mode of the amplifier. When adjusting the OFFSETs
make sure that no current flows through the electrodes. Thus, it is recommended to disconnect
COMMAND INPUT (#15) and to disable the HOLD unit (switch #7 to 0).
Potential Electrode
The potential of the potential electrode is read from the POTENTIAL DISPLAY (#3) of BA-03X.
The display shows the potential of the potential electrode in XXX mV.
Compensate the OFFSET with the OFFSET (#16) potentiometer from the BA-03X.
Current Electrode
Switch the reading of the TEC-B-01 digital display (#9) to VCEL using the electrode selector switch
(#10). The display (#9) shows the potential of the current electrode in XXX mV.
Compensate the OFFSET with the CURRENT ELECTRODE OFFSET (#11) potentiometer.
Note: If a cell model is connected the OFFSET controls should read values around 5, otherwise it is
likely that the headstages or the amplifier are damaged. If microelectrodes are used unusual high
OFFSETs are a sign of badly chlorinated silver wires or unwanted grounding of the bath.
5.3. Electrode Resistance Test
The electrode resistance is dependent on the tip diameter of the electrodes and may reveal whether
electrodes are broken or clogged. Therefore, a resistance measurement test for the CURRENT
ELECTRODE microelectrodes is included in the TEC-B-01. The respective test for the POTENTIAL
ELECTRODE is included in the BA-03X. The test operates independently of any other adjustments,
assuming that all microelectrodes are in contact with a grounded bath (zero potential). The measured
resistance is independent of tip potentials and is automatically displayed on the respective digital
display in M. Furthermore, the electrode resistance can be tested even if the electrode is inside a cell!
The measurement is performed by applying square current pulses of ±10 nA to the respective
microelectrode. The voltage deflection caused by this injection is recorded and processed to give a
direct reading in Mon the digital display.
Important: The electrode resistance test is also a test of the correct function of the respective
headstage.
The resistance test gives only a rough estimate of the electrode resistance. The value for the current
electrode is dependent on the calibration of the current headstage (see chapter 5) and the reading is
correct only in position x1.

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Potential Electrode (BA-03X)
Set the ELECTRODE RESISTANCE (#13) switch to CURRENT ELECTRODE. The upper digital
display (#10) shows the resistance of the current electrode in XX.X M.
Current Electrode (TEC-B-01)
Push the ELECTRODE RESISTANCE PUSHBUTTON (#33). The left digital display (#3) shows
the resistance of the potential electrode in XX.X M.

Important: Since the amplitude of the current pulses is relatively small (at least for oocytes) the
electrode resistance can be checked even if the electrode is inside the cell!
5.4. Capacity Compensation
The frequency response of the potential electrode (low-pass characteristic due to stray capacities) is
compensated for by a feedback circuit ("negative capacity" compensation, CAPACITY
COMPENSATION) and a "driven-shield" arrangement (for an overview see Ogden 1994). Since in
oocyte experiments microelectrodes are usually in the one Mrange or below for most experiments
it is not required to use the CAPACITY COMPENSATION.
The tuning of the capacity compensation control is performed using pulses applied to the COMMAND
INPUT or pulses provided by the electrode resistance test circuit. The TEC-B-01 has to be in CC mode
(see chapter 5.5).
With the cell model connected or the electrode in the bath the CAPACITY COMPENSATION control
is turned clockwise until there is no artifact on the POTENTIAL OUTPUT PEL.
Important: Capacity compensation is based on positive feedback. Therefore overcompensation causes
oscillations which can damage the preparation or the recording electrodes. Therefore the control must
be handled with care and before impaling a new cell it must be set to 0.

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5.5. Testing Operation Modes
Current Clamp
The cell's response to current injections is measured in the current clamp (CC) mode. Current injection
is performed by means of a current source connected to the current injecting microelectrode.
Important: In current clamp, the current stimulus is applied to the BA-03X. In DUAL mode,
STIMULUS INPUT scalings are adapted for oocytes. STIMULUS INPUT (#23) is scaled to 0.1 µA/V
and STIMULUS INPUT (#24) is scaled to 1 µA/V.
Set the amplifier to CC mode using the MODE OF OPERATION switch (#1).
If not already done tune the BIAS current to 0 (see chapter 5.1).
Set the CURRENT OUTPUT SENSITIVITY (#5) to 1.
Compensate the offsets of the current- and voltage electrode (see chapter 5.2).
Set Rmat the cell model to 10k (see chapter 4.3).
Set the holding current to –1 µA using the HOLD potentiometer (#6) (setting: 100, reading:
-1.00 µA) and the HOLD current polarity switch (#7) (set to -).
Make sure that the display selector switch (#10) is set to ICEL and the ELECTRODE
RESISTANCE test is not active.
The POTENTIAL display (BA-03X) should read –10 mV (according to Ohm's law). The
voltage at PEL (#36) should be –100 mV.
Remember: The voltage at PEL is the membrane potential multiplied by 10!
Disable the holding current and apply a test pulse of 2 µA to the cell model by giving a voltage
step of 2 V to STIMULUS INPUT (#23). The length of the test pulse should be at least 50 ms.
You should see a potential step of 200 mV amplitude at POTENTIAL OUTPUT (#36). Due to
the membrane capacity the step is smoothed.
Note: If you expect the POTENTIAL display to show the value of the potential step (in this case 20
mV amplitude) remember that the display is rather sluggish and may not display the right value
(depending on the length of the step). The same is true for the CURRENT display.
Voltage Clamp
In voltage clamp mode, the membrane potential is forced by a controller to maintain a certain value or
to follow an external command. That allows measurement of ion fluxes across the cell membrane. This
is the most complex mode of operation with the TEC-B-01. Special precautions must be taken while
tuning the control circuit in order avoid stability problems.
Make sure that the amplifier works correctly with the cell model in CC mode (see above).
Set the holding potential to –50 mV using the HOLD potentiometer (#6, setting: 050, reading:
050 mV) and the HOLD potential polarity switch (#7, set to -).

Set the CAPACITY COMPENSATION (#13) to 0 and the GAIN (#2) to 1.

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Enable the OSCILLATION SHUTOFF unit from BA-03X with a moderate THRESHOLD
(DISABLED / RESET switch (#32)in middle position, OSCILLATION SHUTOFF LED
green, THRESHOLD potentiometer set to a low value, but not to the most left position)
Set the TEC-B-01 amplifier with the MODE OF OPERATION switch (#1) to VC mode.
The BA-03X POTENTIAL display should show the holding potential of –50 mV and the TEC-
B-01 display (ICEL) the holding current of –5 µA (according to Ohm's law).
It is very likely that the display shows a holding potential of slightly less than –50 mV because
the controller is in GAIN ONLY mode and the GAIN is low. Increasing GAIN and activating
the INTEGRATION will enhance the control loop and therefore increase accuracy.
Hint: If the system oscillates as soon as you switch to VC mode switch back to CC mode and check
the settings. GAIN too high? CAPACITY COMPENSATION not 0? THRESHOLD potentiometer of
the OSCILLATION SHUTOFF unit at the most left position? RS-COMP. not switched OFF?
Apply a test pulse of 20 mV to the cell model by giving a voltage step of 0.2 V to COMMAND
INPUT (#15). The length of the test pulse should be at least 30 ms.
You should see a potential step of 200 mV amplitude at BA-03X POTENTIAL OUTPUT
(#36).
Note: If you expect the POTENTIAL display to show the value of the potential step (in this case +20
mV amplitude, i.e. –30 mV) remember that the display is rather sluggish and may not display the right
value (depending on the length of the step). The same is true for the CURRENT display.
5.6. Tuning the VC mode
In VC mode there is the problem that the voltage step is often not strictly angular shaped. But, for
instance, increasing the clamp speed by tuning the CAPACITY COMPENSATION of the potential
electrode or increasing GAIN also increases noise. Therefore, the settings of the different parameters
result always in a compromise between the stability, accuracy, noise and control speed. In this chapter
we will give some practical hints, how to optimize the accuracy and speed of the clamp. The
theoretical background of adjustment criteria is discussed in chapter 9 (see also Polder and Swandulla,
2001).
The main considerations are: Do I expect rapid or slow responses to voltage changes? How much noise
can I accept? Is it possible to use electrodes with low resistance?
General: The speed and accuracy of the voltage clamp control circuit is mainly determined by the
question how much current can be injected and how fast can this happen. Thus, the more current the
system can inject within a short time the better the quality of the clamp (see chapter 9).

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General Considerations
The key to accurate and fast recording is a properly built setup.
Make sure that the internal system ground is connected to only one point on the measuring
ground and originates from the potential headstage. Multiple grounding should be avoided; all
ground points should originate from a central point. The electrode used for grounding the bath
should have a low resistance so that it can pass large currents.
Use electrodes with resistances as low as possible.
Keep cables short.
Check regularly whether cables and / or connections are broken.
Make sure that chloriding of silver wires for the electrodes is proper and that there are no
unwanted earth bridges, e.g. salt bridges originating from experimental solutions.
Only if no intracellular series resistance is considered TEC system can be tuned according to one of
three optimization methods (see also chapter 9):
1. the “linear optimum” (LO) that provides only slow response to a command step and a maximal
accuracy of 90-97%.
2. the "absolute value optimum" (AVO) that provides the fastest response to a command step with
very little overshoot (maximum 4%) or
3. the "symmetrical optimum" (SO) has the best performance compensating intrinsic disturbance
signals but shows a considerable overshoot (maximum 43%) to a step command.
Under consideration of an existing intracellular series resistance these methods cannot be applied.
Instead, a series resistance compensation can be introduced to optimize clamp performance (see also
chapter 9.2).
Three control modes are implemented to adapt the TEC-03X to the needs of the user:
1. NORMAL fits to many users. In this mode a good compromise between speed, accuracy,
noise and stability is achieved. The normal mode can be optimized by the LO
method (see above).
2. SLOW for relative slow recordings (e.g. ligand activated currents). In this mode accuracy
and stability are increased while speed is decreased. Optimization is done
according to the AVO- or SO method (see above).
3. FAST for very fast recordings (e.g. fast voltage activated currents). In this mode speed
and accuracy are increased but the system is very sensitive with a higher noise
level and tuning requires more experience. Optimization is done by adjusting the
amount of current proportional gain of the SERIES RESISTANCE
COMPENSATION and optimal positioning of the electrodes (see chapter 0).
Important: First use a cell model for the tuning procedure. You will get familiar with the different
settings and the consequences for the system without any damage to cells or electrodes.

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Tuning Procedure
Before you switch to VC mode tune all parameters related to the recording electrodes (offset,
capacity compensation etc.) in CC mode, set GAIN to a low, save level and the control mode
switch to NORMAL, GAIN ONLY (see chapter 5.5). Activate the OSCILLATION SHUTOFF
unit!
Switch to VC mode and apply identical test pulses to the cell model.
The controller is now in P-mode (proportional only). Watch the potential output and increase
the GAIN so that no overshoot appears.
If you a working on slow currents
Switch the control mode switch to SLOW, INTEGRATION to activate the integrator. The
controller is now in PI-mode (proportional-integral). Tune the GAIN again (see above).
Watch the potential output and tune the time constant until the overshoot of the desired tuning
method appears (see also Figure 6).
LO
Only a P-Controller is used. The response to a
command step is slow and has no overshoot
(potential output). The response to a
disturbance e.g. an activating channel is slow
and has a large deviation.
AVO
A PI-Controller is used. The response to a
command step is very fast with 4% overshoot
(potential output). The response to a
disturbance e.g. an activating channel is slow
and has a slight deviation.
SO
A PI-Controller is used. The response to an
unsmoothed command step is fast with 43%
overshoot (potential output). The response to a
disturbance e.g. an activating channel is very
fast and has a slight deviation.
Figure 6: tuning VC according LO, AVO or SO. The potential output is shown.