Dagan 2400A User manual

2400A
Extracellular Preamplifier
Operating Manual
Warning: This instrument is not designed or intended for use in
human applications or human experimentation
深圳市净康科技有限公司
地址：深圳市龙岗区南湾街道吉厦社区沙平北路 111 号 6008
王经理 15813841944（微信同号） QQ : 422612157
电话：[phone] 邮箱：[email protected]
网址：http://www.3000buy.com

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CONTENTS
I. GENERAL INFORMATION
A.INTRODUCTION 7
B. INSTRUMENT AND ACCESSORIES 7
C. SPECIFICATIONS 8
D. OPTIONS/ Input Connectors 9
II. DIRECTIONS FOR USE
A. INSTALLATION 10
1. Line Voltages and Frequency
2. Rack Mounting
3. Bench Use
4. Cleaning
B.OPERATION
1. Electrode 11
2. Stain 11
3.CurrentPump 12
a) Current Pump Compliance 12
b) External Pump Level Reference 12
c) Auxiliary Pump Output 13
d) Z Test (Impedance Test) 13
4. Preamplifier 15
a) Use of High and Low Cutoff Filters 16
b) Monitor Amplifier 17
5. Probe 18
a) Capacitive Neutralization Control 18
b) Probe Input Parameters 19
c) Probe Input Connector 20
d)SystemGrounding 20
e) Physical Probe Placement 20
C. MODEL B (external DC/Battery operation) 22
D.SERVICING 22
E.GUARANTEE 23
DAGAN CORPORATION Minneapolis, Minnesota USA

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I GENERAL INFORMATION
A. INTRODUCTION
The DAGAN Model 2400 EXTRACELLULAR PREAMPLIFIER CURRENT
PUMP is a low noise preamplifier system for extracellular recording
with both glass and metal microelectrodes or micropipettes.
The high input impedance assures faithful reproduction from
electrodes ranging into the hundreds of megohms. In addition to
producing low noise voltage preamplification, the 2400 is unique in
that it also provides an audio amplifier for audible monitoring of the
preamplifier output and two types of current injection to the
microelectrode. One type is used for high current cell staining and
the second is a precise ideal constant current source capable of both
front panel and external analog programming control of magnitude
and polarity. It is potentially useful for cell staining, iontophoretic
drug injection and as a stimulating current (polarize or depolarize).
In addition the Model 2400Z uses the CURRENT PUMP for
microelectrode resistance measurements.
The 2400 also provides optimum bandwidth tailoring for maximum
signal to noise ratio by incorporating both active high pass and low
pass push button switch selection filters. And to reject AC line noise,
an independently, operated LINE NOTCH FILTER provides a 200 to 1
reduction in 60 Hertz interference. When powering the 2400 from
standard AC power lines, no batteries are ever needed to achieve
the low noise performance.
The 2400 is packaged within an attractive, heavy-duty cabinet for
either rack or bench mounting. When used by itself or as a
component of a larger system, this instrument will truly become an
indispensable laboratory tool.
B. INSTRUMENT & ACCESSORIES
The Model 2400A is shipped with the following standard accessories:
Rack adapter (handles/bracket assemblies).
Probe mounting rod for micromanipulator

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C. SPECIFICATIONS
PREAMPLIFIER
NEUTRALIZATION: 15 turn control located on probe. Range is 0 to 100
pF.
INPUT IMPEDANCE: Greater than 10,000 Megohms
INPUT CONNECTOR: Miniature co-axial slip-on
OUTPUT: 10 ohms impedance. 20 volt peak to peak,
BNC connector
GAIN: 50; 100; 200; 500; 1,000; 2,000; 5,000; or 10,000 ± 1%
OVERLOAD RECOVERY: Recovery is very fast, usually
one-half to a few milliseconds except for just after
STAIN. Recovery is then 20 to 40 seconds.
NOISE: Due to Amplifier and Source Resistance; (takes
into account current and voltage noise)
CALIBRATE GENERATOR: 100 uV ± 1%, Peak to Peak Square Wave. 150
Hz
LINE NOTCH FILTER: Standard 60 Hz. (optional 50 Hz.) The rejection ratio
is 200 to or, 46 dB.
HIGH FREQUENCY FILTER: Active 20 dB/decade, push button switch
selection 3 dB points are; 100, 300, 1K. 3K, 10K, 30K and 100K Hz.
LOW FREQUENCY FILTER: Active 20 dB/decade, push button switch
selection 3 dB points are 0.3, 1.0, 3.0, 10, 30, 100, and 300 Hz.
AUDIO MONITOR: An internal audio power amplifier monitors the
PREAMPLIFIER output. Sound level is controlled by the MONITOR control.
Output is through a phone jack located on rear panel. An 8 ohm speaker,
or external computer type powered amplifier is recommended.
CURRENT PUMP
PUMP LEVEL:
(1) EXTERNAL: An analog voltage between minus 10
to plus 10 volts into the EXT REF BNC jack generates
a current between minus 1000 nA to plus 1000 nA.
(2) INTERNAL: The INTERNAL position enables the 10
digital dial current setting. The dial is read out
in nA, and has a range of 0 to 1000 nA. Polarity is determined by
the PUMP POLARITY switch.
Z TEST: A signal 2 Hz 100mV per megohm
STAIN
A POSITIVE (for Metal electrodes) or NEGATIVE (for Glass electrodes)
voltage of 15 volts limited by 10,000 ohms is fed into the electrode.
ELECTRODE (PROBE MODE)
A four station push button switch selects the mode of operation by
connecting the probe input connector to the four functions via a reed relay
located in the probe. The four functions are:

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(1) STAIN: The high level STAIN current is fed to the microelectrode.
(2) CURRENT PUMP: The CURRENT PUMP section of the instrument is
connected through the probe to the electrode. The CURRENT PUMP
is always available through the AUX PUMP OUT BNC jack.
(3) PREAMPLIFIER: The probe and audio monitor amplifiers are connected
to the electrode.
(4) EXTERNAL: The electrode is connected to the EXTERNAL BNC sack. This
position gives direct access to the electrode for passage of any
voltage or current.
GENERAL
POWER: 115v AC, 60 Hz, 6 Watts (optional 230v AC, 50 Hz, 4 Watts)
DIMENSIONS:
MAINFRAME: 43.2 cm W (17") X 34.3 cm D (13k") X 13.3cm H (5
1/4”) (for Rack mounting, handle and brackets make width 48.3 cm
(19").
PROBE: 5.7 cm (2Y4") X 3.2 cm (PA") X 2.5 cm (1") less mounting
plate. Detachable rod is 0.63 cm dia. (1/4 ") X 7.6 cm long (3").
Probe to Mainframe cable is 7 conductor, low noise shielded, 3
meters long (10').
WEIGHT: 10Kg. (20 pounds)
D OPTIONS/ Input Connectors
2400 OPTIONAL HEADSTAGES
2410A Standard Capacitive Neutralized Single ended probe and
cable with connector.
2430A Optional Differential probe for the 2400A System
Input Adapters and Connectors
8012 Additional co-axial input connector
HB120 and HB180 Glass Microelectrode Holders for BNC option input
1mm pins for Tip Jack Option (Order# P657-5 (set of 5))

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II DIRECTIONS FOR USE
A. INSTALLATION
1. LINE VOLTAGES AND FREQUENCY
The serial number label on the instrument rear panel also contains
the line voltage and frequency. A voltage marked 115v AC indicates
the power supply is wired for voltages from 100 to 125v AC.
A 230v AC marking indicates a 200 to 250v AC range. The power
supply will operate from 50 or 60 Hz without modification. The
frequency indicated on the label identifies the frequency of the line
notch filter.
2. RACK MOUNTING
The 2400 is shipped with its rack adapters (handles and brackets)
in place. It is designed for use with a standard 19” rack.
3. BENCH USE
If desired, the rack adapters may be removed to allow for more
space on the bench.
4. CLEANING
Use a soft cloth and mild soap to maintain the dead front
appearance of the front panel.

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B. OPERATION
ELECTRODE
The ELECTRODE control switches provide a unique
combination of microelectrode terminations~ A push of
the button changes the 2400 system from (1) a high
current stain generator for marking recording sites to a,
(2) controlled positive or negative ideal current source
up to 1000nA to (3) a low noise neutralized preamplifier
to your microelectrode for any future need that you
may encounter. All this without ever touching the
probe or the microelectrode.
STAIN
Your microelectrode recording site can be marked for
easy visual identification by using either the STAIN
switch or the controlled but smaller currents from the
CURRENT PUMP. The STAIN generator provides a high
level resistive limited current with polarity selections
for use with both metal and glass electrodes.
The 2400 also provides for any future stain requirements you may
have by giving you direct access to the electrode via the EXTERNAL
BNC CONNECTOR.

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CURRENT PUMP
The CURRENT PUMP provides a precisely regulated current from 0 to
plus or minus 1000 nA for injection of dyes or drugs from the
microelectrode by iontophoresis. The currents can be injected
through the probe into the microelectrode by pushing the
ELECTRODE switch to the CURRENT PUMP position.
If the need should arise for the CURRENT PUMP to be terminated in
an electrode other than the recording electrode, its output current is
always available at the AUX PUMP OUT BNC connector. With the
PUMP LEVEL switch set to the INTERNAL position, the current
magnitude is set by the ten-turn digital readout dial. The polarity is
set by the PUMP POLARITY switch. The OFF position of this switch
programs the ideal current generator to zero nA output, this is a
quick means of going from the dialed CURRENT PUMP level to zero
nA.
Supplying an external bipolar analog signal into the EXT REF BNC
jack with the PUMP LEVEL switch set to EXTERNAL allows the ideal
current source to be programmed externally by the magnitude and
polarity of the reference signal. (Interfaces directly with the D/A
converter output on any computer.)
a) CURRENT PUMP COMPLIANCE
The combination of the microelectrode resistance and the current
level setting of the CURRENT PUMP dial should fall into the darkened
area on the graph at left if linear operation of the CURRENT PUMP is
to be assured. The product of the CURRENT PUMP output (digital dial
reading if using the INTERNAL position of the PUMP Level switch)
and the microelectrode resistance
should be less than 14 volts. For situations requiring higher
compliances than 14 volts the DAGAN model 6400 Current
Generator system (40 volts compliance) is recommended.
b) EXTERNAL PUMP REFERENCE
Using a BNC connector, inject a DC analog voltage within -10 to +10
volts into the EXT REF jack. The input resistance of the CURRENT

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PUMP External Reference input is one meghom. An output current of
1nA for each 10mV of reference voltage will be available either
through the probe or the AUX PUMP OUT BNC connector.
c) AUXILIARY PUMP OUTPUT (AUX PUMP OUT) USE
The output of the current generator may be obtained at any time
from this connector. Current injection through the probe (by placing
the ELECTRODE switch to CURRENT PUMP) and concurrently through
the AUX PUMP OUT connector will result in division of current
between these two loads and thus should not be used
experimentally.
MEASUREMENT OF MICROELECTRODE RESISTANCE
A front panel mounted push button switch may be operated at any
time (the ELECTRODE switch must also be placed to the CURRENT
PUMP position) to instantaneously provide a visual indication of the
microelectrode resistance via the PREAMPLIFIER OUTPUT BNC
connector. A 2 Hertz waveform will appear on the oscilloscope
monitoring the OUTPUT. Each 100mV of peak-to-peak amplitude
indicates a microelectrode resistance of one megohm
(i.e.,100mV/megohm). Thus, a 20 megohm microelectrode
resistance will appear as a 2 volt peak-to-peak signal.
Since the CURRENT PUMP is connected to the microelectrode for this
check, it will pump or inject its programmed DC current into the
microelectrode until the resistance test pushbutton is depressed. At
this time a 2 Hertz 100nA peak-to-peak square wave is injected into
the microelectrode via the probe. Since it is a regulated current
signal, a voltage corresponding to this current flow through the
microelectrode resistance will reflect the magnitude of this
resistance.
When using the CURRENT PUMP for the resistance check the AUX
PUMP OUT BNC front panel connector should not be used since this
would divert a portion of the test current away from the
microelectrode and result in an incorrect reading.
Some risetime effects will be noticed since the CURRENT PUMP
output is internally "loaded" with a capacitance of l000pF. Thus, for a
10 megohm microelectrode or test resistor, a RC time constant
(63% of risetime) of 10ms will result.

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In instruments equipped for microelectrode resistance
measurements (2400Z), the CALIBRATE generator will be modified
to a 2 Hz output. The model 2400 is normally supplied with a 150 Hz
CALIBRATE generator.

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PREAMPLIFIER
The heart of the 2400 system is its versatile preamplifier section
made up of a high gain, low noise neutralized preamplifier, active
filters, and an audio amplifier. The neutralized input capacitance
allows risetime signals to be viewed with high microelectrode
resistances.
Since extracellular and microiontophoretic recording can involve
microelectrode resistances into the tens of megohms, current noise
(in addition to voltage noise) becomes an important consideration.
The 2400 system preamplifier is designed for use with both high and
low impedance electrodes. In all situations it will provide noise levels
close to the Johnson noise theoretical minimum (produced by the
microelectrode resistance).
The voltage gain of the preamplifier section is very high (switch
selection of 50; 100; 200; 500; 1,000; 2,000; 5,000; or 10,000). No
other additional amplification should ever be needed between the
microelectrode and the recording instrumentation.
A full complement of active filters means that frequency response
can be tailored to provide maximum signal to noise ratio. The seven
frequencies for both the high and low frequency cutoff filters were
chosen to provide for a complete range of recording bandwidths.
Selection is made by convenient, fast action, push button switches.
By switching on the twin-tee active LINE NOTCH FILTER,
interference problems caused by 60 (or 50) hertz power lines are
eliminated.
The internal audio power amplifier fulfills the requirement for audio
monitoring of the preamplifier output. The audio level is determined
by the MONITOR control and a separate 8 ohm speaker (available as

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an option) plugs into the instrument back panel to provide sound
where you want it.
A Calibrate switch allows a precise signal to be passed from the
preamplifier to calibrate recording or viewing instrumentation.
a) USE OF HIGH AND LOW CUTOFF FILTERS
The active filter network provided in the 2400 is virtually a complete
instrument in itself. The sharp 40 db/decade rolloffs in response on
both the low and high cutoff filters provide clean segmenting of the
frequency spectrum into a well defined bandwidth. This capability
will optimize your signal level with respect to the white noise
background.
The primary sources of this noise are typically within the preamplifier
and also the microelectrode resistance. Careful attention to design,
component selection, testing, and layout in the 2400 system have all
but eliminated the preamplifier as a major noise contributor.
Noise generated by the microelectrode resistance (Johnson Noise)
can also be controlled to some degree by manipulating the
bandwidth or frequency response of the preamplifier's output. Since
Johnson Noise is frequency dependent (in ideal situations also linear
with frequency) it may be controlled by limiting the lower and
primarily the upper limits of the preamplifier frequency response. As
can be seen in the defining equation of Johnson Noise, a factor of
four decrease in bandwidth will reduce the background noise by a
factor of two.
E = Square root of: 4KTBR
where: E = Johnson Noise (rms)
B = Bandwidth
R = Resistance
K = Boltzman's constant (1.38 x 10E23)
T Temperature in degrees Kelvin
Multiplying the value E by a factor of five will provide a good
indication of the peak-to-peak voltage level of the expected noise
with a 99% probability.
b) MONITOR AMPLIFIER
The power level of the MONITOR amplifier is purposely kept low (1/2
watt) so that interference problems are minimized. To take

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maximum advantage of the audio drive available the speaker should
be located within five to ten feet of the listening area. An 8 ohm
large (efficient) speaker, or a computer type powered speaker is
recommended.
It is potentially possible to overdrive the MONITOR amplifier if large
(several volts at the OUTPUT BNC connector) signals are used. To
prevent this from occurring and introducing possible interference
into the preamplifier input, never use a MONITOR level so high as to
cause oscillation and distortion in its output.
If the MONITOR amplifier provision is not used the output binding
post on the rear panel should not be terminated and the MONITOR
control should be at its minimum position.
c) CALIBRATE SWITCH
A Calibrate switch sends a 100mV square ware signal through the
output so that any recording equipment can be set up.
A rear panel mounted BNC PULSE TEST 10:1 allows you to inject a
calibration signal through the 2400A (after the GAIN) to check
external recording equipment. For example, a one volt signal would
be seen as a 100mV signal at the OUTPUT BNC.

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PROBE
An ultra low noise experimental setup and the absence
of capacitive loading effects are made possible by the
use of a probe head stage containing the first
preamplifier gain block and also all circuitry needed for
the other microelectrode terminations.
Capacitive neutralization is at your fingertips with a high resolution
neutralization control located on the probe. This feature gives you
the capability to fine tune signal risetimes when your
microelectrode’s resistances are greater than a few megohms.
A low noise shielded probe cable is so flexible that the lightweight
probe head stage will always stay where you want it. The ten foot
cable and rugged chassis connector make for fast and simple
connection to your experimental setup. A slide-on miniature co-axial
input connector mates with a wide variety of female connectors
made by several manufacturers. Two different mating connectors are
supplied with the 2400 initially. A removable three inch long rod
allows the probe to be mounted directly in your micromanipulator. A
flat removable probe mounting plate is furnished for setups that
necessitate permanent mounting of the probe to a variety of
surfaces and equipment.
a) CAPACITIVE NEUTRALIZATION CONTROL
The neutralization control is a 15 turn trimpot located at the
mounting rod end of the probe. It controls the amount of positive
feedback supplied to the input of the first gain stage of the
preamplifier. It effectively neutralizes up to 100pF of stray input or
microelectrode capacitance by correcting for the degradation in
signal risetime caused by these capacitances in conjunction with the
microelectrode resistance. The algebraic product of the micro-
electrode resistance and the stray capacitance is equal to one "time
constant" or about the length of time in seconds it will take the
signal's leading edge to rise to 63% of its total amplitude. Thus
decreasing this capacitance by neutralization (canceling it with the

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negative neutralization capacitance fed back to the probe input) will
result in a much faster risetime.
The neutralization control is preadjusted at the factory and in many
cases will never need additional attention. For very high
microelectrode resistances (above 10 megohms) or experimental
setups with a large amount of stray (or a co-axial cable)
capacitance, slight adjustments from time to time will be desirable.
Adjustments can be accomplished both when the 2400 is terminated
in (1) a microelectrode or in (2) a test resistor.
(1) It may be adjusted during an experiment by simply
introducing a square wave between the 2400 grounding lead
(shield of co-axial input cable or mounting rod or bracket) and
the experiment ground reference wire. Rotate the trimpot until
the leading edge of the square wave is vertical and displays no
more RC time constant (exponential) effects.
Actual signals may also be used if it is inconvenient to
introduce a square wave in the above manner. But because of
the lack of a clear rise time (or vertical leading edge) in most
situations the best approach will be to rotate the neutralization
trimpot until oscillations start, then back off one-half turn. This
should be very satisfactory in the majority of cases.
(2) The neutralization control may be adjusted to compensate
for fixed added input capacitance (such as a short length of co-
axial cable from the micro-electrode internal to the 2400 probe
input connector) in the following manner: Terminate the probe
input to ground through a 10 megohm resistor (carbon
composition type may be used). Now rotate the control until
oscillations are visible at the PREAMPLIFIER output BNC
connector. Back off one-half turn. This is also a good method
of calibrating the neutralization control if it is normally not
used but you desire optimum neutralization.
(b) PROBE INPUT PARAMETERS (PREAMPLIFIER MODE ONLY)
When operating in the PREAMPLIFIER mode, care should be
exercised with regard to static voltage discharge to the probe input.
Although the input is designed around a very rugged dual junction
FET amplifier and is isolated from the input through a 10K resistor,
extreme abuse (several hundred volts) may cause some damage.
The input stage is DC coupled to the microelectrode in the
PREAMPLIFIER mode (it is disconnected via a reed relay in all other
modes) and is operated at a gain of 10. For this reason, input DC
offsets should be less than one volt for linear recording. The use of a

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DC coupled input stage allows extremely fast preamplifier recovery if
overloads or open circuits occur.
c) PROBE INPUT CONNECTORS
The 2400A comes with BNC connector, Mini Coaxial, 1mm Tip Jacks,
or Phone Jack
BNC (standard in 2005)
Mates with Dagan HB120 and HB180 microelectrode holders for
glass pipettes.
Mini Coaxial (standard before 2005)-
The 2400's input connector mates with the DAGAN part number
8012 Mini Coaxial connector with 15 cm of miniature coaxial cable
attached. Coaxial cable typically has a distributed capacitance of
48pF per foot, so its length should be kept to a minimum (few
inches).
1 mm Tip Jacks
Mates with standard Tip Jack connectors (Order# P657-5 (set of 5))
Phone Jack
Mates with earphone mono connecters.
d) SYSTEM GROUNDING
Either the probe or the mainframe cabinet may be grounded to your
experiment for the reference connection. The probe is preferable for
the lowest noise setup; however, experimentation with grounding
may provide a better noise level in unique situations. For all common
experimental setups the probe is grounded by either tying into the
shield of the co-axial input cable or connection to the probe
mounting rod screw. The mounting rod or plate may also serve as
the 2400 system's ground connection to your experiment.
Any number of 2400's or any other amplifier using a real ground
reference may be used at the same time on the same experiment
without cross-talk or mutual interference.
The mainframe may be grounded via either of the front panel BNC
connector bodies or alternatively by the binding post located on the
rear panel.
e) PHYSICAL PROBE PLACEMENT
Because of the neutralized input design of the first gain stage of the
PREAMPLIFIER, the 2400 has a "single ended" input (one side of the

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differential FET amplifier connected to ground). To achieve maximum
advantage of the low noise preamplifier input, the probe should be
located as close as possible to the microelectrode. The usual
procedure is to use a 4 to 6 inch piece of small diameter co-axial
cable to connect the microelectrode internal to the 2400 probe input
connector.
To aid in mechanical mounting of the probe, either the mounting
plate (secured to probe by the 4 cover screws) or the mounting rod
may be used. The cover is glued in place to seal the probe from
moisture and thus will not come off even if the four mounting screws
are removed. At least one screw is needed to insure electrical
connection of the cover to the probe and thereby provide shielding.