Dagan IX2-700 User manual

IX2-700
Dual
Intracellular Preamplifier
Operating Manual
Version 1.1
Dagan
Corporation
2855 Park Avenue
Minneapolis, MN 55407 USA
[phone]
Fax: [phone]
Email: [email protected]
Web: www.DAGAN.com
Warning: This instrument is not designed or intended for use in human applications or human experimentation.

IX2-700 Dual Intracellular Preamplifier
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TABLE OF CONTENTS Page
IX2-700 Block Diagram 2
Introduction and Features 3
ControlDescription 4
Operation 7
Specifications 11
Accessories 12
Warranty/Services/Repairs 13

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IX2-700 Dual Intracellular Preamplifier
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INTRODUCTION
The IX2-700 is a dual channel microelectrode preamplifier
designed to serve a wide variety of applications including:
Single and Two Channel intracellular recording; Single and
Two Channel extracellular recording; Ion-Selective Electrode
Amplifier; Teaching application requiring ease of use.
The IX2-700 is a complete instrument with DC and pulsed
current passing capability, filtering, electrode impedance
testing, and a back lighted (for dark labs) LCD voltage and
current meter.
FEATURES
• Small Box Probe in five current ranges with automatic
decimal point selector on current meter.
• Different output and Cross Coupling control for ion-
selective electrode.
• Gatable independent Step Command current generator
with ten-turn programming dial
• Buzz with independent amplitude control for each
channel to facilitate cell penetration.
• Small size...takes up less rack space, yet is uncluttered,
easy to use, with well defined controls.
• Optional X1000 Voltage Gain AC Coupled Headstage
for extracellular recording (Model 8024-15).

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CONTROL DESCRIPTION
3.5 DIGIT LCD METER
The meter has five functions. They are:
(1) Measuring the Channel 1 output voltage at a gain of one (i.e. I Vm)
(2) Measuring the Channel 2 output voltage at a gain of one (i.e. 1 Vm)
(3) To measure the potential difference between Channel 1 and Channel 2.
(4) To measure the membrane current Im from Channel 1 scaled by the
headstage for automatic decimal point on the meter.
(5) To measure the membrane current Im from Channel 2 scaled by the
headstage for automatic decimal point on the meter.
BUZZ OPERATION
The buzz or tickle function contained in the IX2-700 is used to impale an
electrode in the cell. The IX2-700 has a controlled buzz magnitude. Start with the
Buzz Magnitude in the counterclockwise or minimum position and increase while
initiating buzzes until you achieve desired cell penetration. (Buzz magnitude is a
trimpot located under the buzz switch).
CAPACITANCE COMPENSATION CONTROL
This control provides input capacitance neutralization. Without this
compensation high frequency signals from a high impedance source such as a
micropipette would be lost because of stray capacitance at the input. Start with this
control at its minimum in the counterclockwise position.
The amount of capacitance compensation available depends on the
capacitance compensation range ordered with the probe you are using. Ranges as
small as 15 pf and as large as 100 pf are available (35 pf standard). Smaller ranges
produce less noise and are ideal for very low capacitance microelectrodes used
with high switching frequencies. The larger capacitance compensation ranges are
ideal for doing typical bridge preamplifier procedures and also switched single
electrode voltage clamping in deep tissue, where the microelectrode has a high
capacitance associated with it.

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OFFSET VOLTAGE CONTROL
This control cancels electrochemical potentials developed between reference
electrodes and the probe input. Offsetting the output level of the amplifier nulls
these potentials. The range is ±200 mV. Be careful not to touch this control during
the experiment, as it will change the baseline.
ELECTRODE IMPEDANCE TEST (Z TEST)
This switch provides a rapid check of electrode impedance. When switched
on, the square wave signal proportional in amplitude to the electrode impedance,
appears at the 10 VmBNC connector. A signal level of 1 mV is equivalent to 1
Megohm of electrode resistance when using a X1 headstage. A X.1 (i.e., divide by
10 headstage) scales this to .1 mV per megohm referred to the input.
DC CURRENT 10-TURN DIAL
The current dial provides a depolarizing (positive) or hyperpolarizing
(negative) current selected by the corresponding Positive/Off/Negative polarity
switch. The range of the current is 100 nA full scale times the headstage multiplier.
Thus, the X .1 headstage would change the full scale dial reading to 9.99 nA. The
current control is linear and the readout corresponds to the actual current selected.
This current is algebraically added to the currents produced by the EXT I BNC
connector and also the Step Current Command Generator, if selected.
BRIDGE BALANCE CONTROL
The bridge Balance Control is used to null out the effects of stimulus current
passing through the recording electrode. The bridge is balanced by turning the
knob on the dial housing. When the bridge is balanced the voltage seen at the
10Vm connector will be nulled to zero and the resistance of the electrode and cell
membrane is read on the dial. The range of the bridge balance dial is 100
Megohms divided by the probe current multiplier. Thus, for the X.1 probe, the
range will be 1000 Megohms. The bridge Balance is disabled when Z Test is used.
STEP CURRENT 10-TURN DIAL
The step current adds to the Holding Current and has ten times the range. It
can be on continuously, if gated on and off by a greater than 3 volt level supplied
to the Gate BNC connectors.

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EXTERNAL I BNC
The External I BNC allows for externally generated step commands at
20nA/V times the headstage multiplier.
1/3/5/10/30 KHZ WB FILTER SWITCH
The low pass filter limits the high frequency response of the amplifier to
minimize noise. The bandwidth should be set to the lowest setting, which will not
distort the desired input signal. The Wide Band WB position removes the filter and
leaves the amplifier with as wide as possible frequency response. The filter switch
only affects the 10 Vm and 100 Vm connector.
CLEAR SWITCH
The Clear Switch can be used to clear blocked microelectrode tips by
passing a large current through the recording electrode. It is also useful or impaling
cells, and typically, the Clear positive will be (100nA X N) the most common
polarity, although negative currents are also available. In addition, the Buzz Switch
is many times useful for clearing a blocked microelectrode and impaling cells.
MONITOR (MON) BNC CONNECTOR
Actual currents being passed through the microelectrode are monitored and
available at the I MON connector. Sensitivity is +10 mV per nA divided by the
headstage multiplier. Thus, for the X.I probe sensitivity is 100 mV per nA. The
usable dynamic range of the I MON connector is +12V. The I MON connector is
unfiltered. Output impedance is 600 ohms.
10 Vm and 100 Vm Output BNC CONNECTORS
These outputs of the voltage recording amplifier scaled up by +10 and +100.
This output is processed by the filter switch and has added to it the Offset voltage.
The output impedance is 600 Ohms and the range is + 12 volts.
IG CALIBRATION
The headstage bias current can be adjusted by shorting the headstage Input
to ground (headstage rod) and setting 10 Vm output to zero using the OFFSET
Control. Then put a 10 to 100 megohm resistor from the headstage input to ground
and then use a small screwdriver or trimpot adjustor for 10 Vm equal zero.

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OPERATION
Each of the two independent channels in the IX2-700 can be used as a
bridge Channels 1 and 2 have Bridge Balance and Holding Current
controls.
PROCEDURE
When beginning, ascertain that the system is grounded properly and that the
noise is low. Connect the current and voltage outputs to an oscilloscope. Set the
gain on the oscilloscope to yield 10mV/div. (i.e., 1mV/ div for the 10V output; also
scale Imon by headstage N). Turn the capacity compensation and bridge balance to
the minimum, and the offset voltage and holding current to zero. Make sure that
the step command and the Z test are also off.
ADJUST DC OFFSET
Insert the electrode tip into the bath solution. Adjust the DC offset control so
that the voltage is at ground potential (ground voltage trace, adjust position on
oscilloscope to desired position, uncouple voltage channel, and return trace to the
same position using the DC offset control).
Z TEST
The Z Test can now be used to determine the resistance of the electrode.
Depress the Z test button. There should be a square wave on the oscilloscope
voltage trace of 1mV/megohm of electrode resistance. This measurement is
obtained by passing a 1nA square wave through the pipette. Note that this
resistance test (scale by headstage multiplier N) disables the bridge balance
control. Providing the electrode resistance is within the range you are interested in
working with, you can proceed to balancing the bridge.
BALANCE THE BRIDGE
The bridge must be balanced to effectively “subtract out” the effect of the
potential drop across the microelectrode, allowing you to record only the events at
the cell membrane. The procedure is as follows:

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Apply a train of current pulses to the electrode. Note that the Z test may not
be used for this as it disables the Bridge Balance control. This can either be from
an external source or from the Step Current Command. You will see a train of
pulses on the voltage trace of the oscilloscope. These pulses are due to the voltage
drop across the series resistance of the microelectrode. Rotate the bridge balance
control clockwise until the pulses on the amplifier output reach a minimum
amplitude. Rotation past the null point will reverse the polarity of the displayed
pulses. Adjust the bridge balance for the best null. The bridge is now balanced and
a stimulus from any source will give minimum voltage at the amplifier output. The
resistance of the electrode can be read on the ten turn dial. The bridge balance may
be locked into this position if desired.
An alternative method of balancing the bridge is as follows: Zero the voltage
trace using the offset control and note the position. Set the holding current to some
value other than zero and switch to either the + or - position. The oscilloscope trace
will depart from its previous position. Adjust the bridge balance control until the
scope trace returns to its initial position. Switch to the opposite polarity and
readjust the bridge balance. When the trace does not move when you switch
polarity, the bridge is balanced.
The main disadvantage with a bridge circuit arises from changes in the
microelectrode resistance. The circuit works on the assumption that the bridge is
balanced for the electrode resistance. Often the resistance of the electrode changes
slightly as you penetrate the cell. In some applications this will not be significant,
while in others it will. One method to attempt to correct for this change is to
balance the bridge after you have penetrated the cell. This method takes advantage
of the time it takes to charge the membrane capacitance. If the pulse duration used
to balance the bridge is sufficiently short, the potential drop recorded will be
predominantly result of the drop across the electrode. However, this does not
account for the local potential that is developed within the cell in the region of the
electrode. For a more complete discussion of this phenomena, see Peskoff and
Eisenberg (1973). Allowing for this generalization, the bridge can be balanced
within the cell (as above), but with very short pulses. Ideally these would be in the
nanosecond range, but 1 msec will usually work. Because both methods (inside
and outside cell) involve approximations, it is a good idea to try balancing the
bridge both ways to see if the results are similar. Another good routine practice is
to check the electrode resistance immediately upon leaving the cell to compare the
values. Data obtained when there is a large discrepancy between these values
should be discarded, as the true membrane potential will be unknown.

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COMPENSATING FOR THE CAPACITY
The capacity compensation control provides capacitance neutralization, or
“negative capacitance” at the headstage input. Without this compensation, high
frequency signal components from a high impedance source such as a
microelectrode would be lost because of stray capacitances at the input. Apply a
square wave (such as in balancing the bridge) to the electrode. Since you have
already balanced the bridge, there should not be a step pulse on the voltage trace of
the oscilloscope. What you will see, however, are capacitative transients at the
initiation and termination of the pulsed current. Turn the capacitance compensation
clockwise until these are at a minimum without overshooting, ringing or
oscillating.
IMPALING THE CELL
With the system calibrated, the electrode in good condition, and the
amplifier compensated, you are ready to penetrate the cell. As the barrel of the
electrode enters the tissue, further adjustments of the capacitance compensation
may be necessary.
As you approach the cell and the electrode tip is abutted against the
membrane, you may wish to use the Buzz feature to aid in penetration. Both
Channel 1 and Channel 2 are equipped with Buzz circuitry of variable amplitude.
The exact configuration and parameters with which you “buzz” your cells is
something that must be determined individually for your particular system. The
type of cell, electrode resistance, and nature of dissection are all factors affecting
the ideal parameters. A bit of trial and error methodology must be employed here.
Finally, the Holding Current may be set at the desired level and the Step
Current Command or an external command current can be directed to that channel.

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DIFFERENTIAL RECORDING
The IX2-700 can be used for differential recording using Channel 1 and
Channel 2. The 10 (V1- V2) output BNC on the front panel is the Channel 1
voltage less the Channel 2 voltage. You must be certain both channels are properly
zeroed with their DC offsets as any offset will also be subtracted from the other
channel. There is an internal trimpot for common mode rejection ratio adjustment
that has been factory set. This adjustment assures that the output is zero when the
outputs from channels 1 and 2 are equal. Should you need to adjust the trimpot,
contact the factory for explicit instructions.
The Cx control is for cross capacitance nulling to adjust for variations in
dynamic response time between Channel 1 and Channel 2.
Since the selection of available probes includes one with an input impedance
greater than 1014 ohms the differential mode may be used directly with ion
selective electrodes (i.e. channel 1 connected to the ion sensitive electrode). The
output resistance is 600 ohms with a range of +/- 13 volts.
UNUSED CHANNEL
If you are only using one of the two channels, either unplug the unused 15
pin rear panel connector or connect the unused headstage input connector through
a resistance or directly to ground (ROD).

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SPECIFICATIONS
Electrode Holders: Low noise polycarbonate in two sizes: 1.0 to 1.2mm
(#HBI2O); 1.5 to 1.8 mm (#HB18O) (order separately)
Headstage: Box Probe, 1.5” x 1.2” x .88”, 4” long, 3/8” rod, BNC
Input Connector
Standard Headstage: N=.l for 20 to 500 Megohm
electrode
Current
Multiplier
Feedback
Resistor Noise
Electrode
Resistance
Input
Resistance
(N) Max I RERMS/BW/Re Range Cp
10 10µA 1MΩ25µv, 10kHz, 1MΩ.2 to 5 MΩ20 pf 1010MΩ
1 1µA 10MΩ50µv, 10kHz, 10MΩ2 to 50 MΩ10 pf/35 pf 1011MΩ
.1(Standard) 100nA 100MΩ50µv, 1kHz, 100MΩ20 to 500 MΩ10 pf/35 pf 1012MΩ
.01 10nA 1GΩ40µv, 100Hz, 1GΩ200 to 5000 MΩ20 pf 1013MΩ
.001 1nA 10GΩ35µv, 10Hz, 10GΩ2 to 50 GΩ20 pf 1014mΩ
Extracellular Recording: Works with 8024 voltage, gain 1000 AC
coupled headstages
Filter Response: Switch selectable DC to 1kHz, 3kHz, 5kHz,
10kHz, 30kHz and Wide Band
Input Bias Current: 1 x 10-12 Amps (Adjustable to zero)
Rise Time to Pulse: Typically 10 microseconds into 10 megohm
resistor (10 to 90%), 50 microseconds into
100 megohm
Voltage Gain: X10 and X100
Output Impedance: 500 ohms all outputs
Offset Voltage: +200mV

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Balance Reading: 0 to 100 megohm divided by headstage
scaling N (ten-turn dial)
Electrode Impedance Test: 1mV per megohm squarewave (N)
Digital Polarization Current Range: 0 to +100 nA (ten-turn dial) scaled by
headstage multiplier N
Gated Stimulus Current: +2 volt to +20 volt level turns on
programmed stimulus step (0 to + 1000nA)
Monitor: 1999 my meter displays channel 1 and 2
voltage and current and channel 1 minus 2
voltage (decimal point is automatically set)
Cross Capacitance Control (Cx): For ion selective electrode balancing
Size: 3 1/2 inch by 19 inch rack
Power: 115/230 50/60 Hz
ACCESSORIES
Electrode Holders (Requires two):
HB12O: 1.0 to 1.2 mm outside glass diameter
HB18O: 1.5 to 1.8 mm outside glass diameter
Option ‘B’ - Bootstrap Headstage Driver (Double Speed)
Model 7001 Spare Box Headstage (Specify N=0.001, 0.01, 0.1, 1, 10)
(comes with BNC input)
8024-15 Extracellular Headstage (AC Coupled, Voltage gain = 1000)

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The Dagan IX2-700 Dual Intracellular Preamplifier is warranted to be free from
defects in construction caused by materials and workmanship for a period of one
year from the date of purchase. During this period, Dagan Corporation will service
your instrument at no charge.
We prefer that any MAJOR service work that might become necessary be
performed in our laboratory. However, you may be able to service your own
instrument if you desire in certain situations. There are a few MINOR problems
that you may correct yourself and not void the warranty. These include changing
the fuses and replacing defective printed cards:
MINOR REPAIRS
For safety, always be sure to disconnect the line power to the
instrument before working inside the cabinet.
MAIN FRAME COVER REMOVAL
Remove the four screws on the top cover and slide it backwards.
PRINTED C1RCU1T CARD REMOVAL
Unscrew the desired PC board locking screws. Unsnap the connectors and
pull them upwards.
FUSE REPLACEMENT
The IX2-700 has a fused power supply. The fuse is located inside the
cabinet on the rear panel printed circuit board. It is easily snapped out for
inspection if the power switch pilot light should fail to function. It is a slow-
blow 1 amp. 250 volt 3AG type.
A phone call to us can usually provide enough data to confirm the problem. We
will immediately ship to you the replacement parts that are necessary to fix the
instrument. If your problem is more serious, or if you prefer that we replace any
faulty cards, please call us first. We will issue you a return authorization number.
You must put this return number on the outside of the box and on the packing slip
or instruction sheet accompanying the instrument. We will immediately repair all
instruments that are accompanied by an authorization number and return them to
you.