WPI 260 User manual

Instrumenting scientific ideas
WORLD
PRECISION
INSTRUMENTS
Model 260
Microiontophoresis Current Programmer
Serial No._____________________
www.wpiinc.com
INSTRUCTION MANUAL
021216

Model 260
World Precision Instruments i
Copyright © 2016 by World Precision Instruments, Inc. All rights reserved. No part of this publication
may be reproduced or translated into any language, in any form, without prior written permission of
World Precision Instruments, Inc.
CONTENTS
ABOUT THIS MANUAL ................................................................................................................... 1
INTRODUCTION .............................................................................................................................. 1
Unpacking................................................................................................................................... 2
INSTRUMENT DESCRIPTION ........................................................................................................ 2
OPERATING INSTRUCTIONS......................................................................................................... 3
Preliminary Instrument Check ............................................................................................... 3
Single Channel Operation....................................................................................................... 3
Two Channel Operation, Hold-Eject..................................................................................... 4
AUTO Operation........................................................................................................................ 4
Compliance Alarms................................................................................................................... 5
MAINTENANCE ................................................................................................................................ 5
Battery Replacement................................................................................................................ 5
ACCESSORIES................................................................................................................................... 6
SPECIFICATIONS.............................................................................................................................. 6
APPENDIX A: APPLICATION NOTES ............................................................................................ 6
Current Injection in Microiontophoresis............................................................................. 6
Constant Current ...................................................................................................................... 7
Current Return .......................................................................................................................... 8
Measuring Current .................................................................................................................10
REFERENCES ..................................................................................................................................10
WARRANTY .....................................................................................................................................11
Claims and Returns ................................................................................................................11
Repairs.......................................................................................................................................11

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Model 260
World Precision Instruments 1
ABOUT THIS MANUAL
The following symbols are used in this guide:
This symbol indicates a CAUTION. Cautions warn against actions that can cause
damage to equipment. Please read these carefully.
This symbol indicates a WARNING. Warnings alert you to actions that can cause
personal injury or pose a physical threat. Please read these carefully.
NOTES and TIPS contain helpful information.
Fig. 1 Model 260 is designed for electroiontophoresis of dyes, drugs and charged
substances from micropipettes.
TIP: For an excellent video introduction of the process, see the Jove video at www.jove.
com/video/2900/microiontophoresis-micromanipulation-for-intravital-uorescence.
INTRODUCTION
The Model 260 Microiontophoresis Current Programmer is a oating, battery-
operated instrument designed for the electroiontophoresis of dyes, drugs and
charged substances from micropipettes. Two identical battery operated current
generators are available. In ordinary use, the two current generators are operated
in parallel providing two distinct currents; one for preventing substances in the
micropipette from outward diusion (the retain or hold current) and the second
for the active ejection of charged material. For pipettes with submicron tips, a hold
current may not be necessary if there is little outward diusion of pipette material.
Model 260 is powered by four standard 9V batteries and 5V DC external power
supply. (Units manufactured before 2015 did not require the 5V external power
supply.) Their life expectancy can be considerably improved if the power switch is
turned o when the instrument is not in use.

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Unpacking
Upon receipt of this instrument, make a thorough inspection of the contents and
check for possible damage. Missing cartons or obvious damage to cartons should be
noted on the delivery receipt before signing. Concealed damage should be reported
at once to the carrier and an inspection requested. Please read the section entitled
“Claims and Returns” on page 11 of this manual. Please contact WPI Customer
Service if any parts are missing at 941.371.1003 or [email protected].
Returns: Do not return any goods to WPI without obtaining prior approval (RMA
# required) and instructions from WPI’s Returns Department. Goods returned
(unauthorized) by collect freight may be refused. If a return shipment is necessary,
use the original container, if possible. If the original container is not available, use a
suitable substitute that is rigid and of adequate size. Wrap the instrument in paper or
plastic surrounded with at least 100mm (four inches) of shock absorbing material. For
further details, please read the section entitled “Claims and Returns” on page 11 of
this manual.
INSTRUMENT DESCRIPTION
The following controls are available for both the Hold and Eject channels.
POWER ON/OFF–Instrument power switch/external 5V DC. To maximize battery life,
turn the power OFF when the channel is not in use.
CURRENT LEVEL–This control varies the current amplitude as indicated on the
ammeter. To prevent accidental current ow via the output terminals, place the
OUTPUT switch in the PRESET position while adjusting current amplitude.
CURRENT RANGE–Selects either 100 or 1000nA current range
MODE SELECT–MANUAL operation allows you to apply a DC current when the
OUTPUT switch is changed from PRESET to ENABLE. AUTO operation requires you
to apply a +5V command potential to initiate the ow of current.
OUTPUT POLARITY–NORMAL indicates that the red output connector is positive
with respect to the black connector. INVERT reverses connector polarity.
AUTO INPUT–If the MODE SELECT switch is in the AUTO position, the AUTO
INPUT connector controls current activation. Five volts positive with respect to the
outer connector shell maintains the current for as long as this voltage is applied. The
CURRENT LEVEL control continues to dictate the actual current amplitude.
OUTPUT–In the PRESET position, the red and black current output terminals are
disconnected from the current generating circuit. ENABLE connects the output
terminals to the current source. If the OUTPUT switch is in the PRESET mode, current
cannot ow out of the instrument in either MANUAL or AUTO operating modes.
CHAS GND–This green binding post is connected to the chassis or metallic enclosure
of the instrument. It should normally be connected to the ground point of your
recording system.

Model 260
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OPERATING INSTRUCTIONS
Preliminary Instrument Check
1. Set the OUTPUT switch to PRESET on either channel. This disconnects the red
and black output terminals and internally short circuits the output of the current
generator.
2. Set the MODE SWITCH to MANUAL.
3. Turn on the POWER switch located just below the current indicating ammeter.
Notice that as the CURRENT LEVEL control is rotated, the ammeter reading
changes accordingly.
4. Set the current ranges and note the similar ammeter behavior.
NOTE: You may easily reach and exceed the ammeter’s maximum reading. If you
cannot reach and exceed full scale on the ammeter, the transistor batteries may
need replacement.
5. If the OUTPUT switch is changed from PRESET to ENABLE at any current
setting, an audible alarm sounds, and a red lamp on the front panel illuminates
to indicate that the output current pathway is an open circuit. (At very low
nanoampere current settings, the alarm may take several seconds to activate.)
6. Check the performance of both channels in the manner indicated above.
7. Ground the CHAS GND green binding post to assure low noise. The instrument is
now ready for use.
Single Channel Operation
Model 260 contains two completely independent oating, battery operated current
generators, which may be operated independently or in parallel connection. As an
independent current generator, you only need to connect your external electrode pair
to the red and black output terminals of channel 1 (HOLD) or 2 (EJECT).
While making these connections and any preliminary control adjustments, the
OUTPUT switch should be in the PRESET position. This will prevent any accidental
current ow.
1. Set the CURRENT RANGE. For currents below 100nA, the 100nA range is
recommended, because you may adjust these low current values with better
resolution in the lower current range.
2. Adjust the CURRENT LEVEL control until the required DC current value is
observed on the channel ammeter.
3. Select the OUTPUT POLARITY desired. NORMAL yields a positive potential at
the red output terminal.

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4. Switch the OUTPUT switch from PRESET to ENABLE to release the required
current from the output terminals. To halt current ow, return it to the PRESET
mode.
Two Channel Operation, Hold-Eject
In “Appendix A: Application Notes” on page 6 is a description of the electrophoretic
release of charged substances from micropipettes, which often requires the use of a
second current to counter the outward diusion of material from the delivery pipette.
This current has been referred to in the literature as “backing, holding or retaining”
current. It cause a small current to ow in a direction that osets the spontaneous
leakage of the active agent from the pipette until it is required.
1. Connect a shorting wire or jumper to tie the red OUTPUT terminals of the HOLD
channel and the EJECT channel together.
2. Connect an identical jumper wire between the black OUTPUT terminals. This
eectively connects the two current generating channels in parallel. Current
does not ow from one channel into the other, but it will sum algebraically in the
common electrode pathway, if both channels are operating simultaneously.
3. Place both channels in the PRESET mode to prevent accidental current ow
during set up.
4. Set the polarity and current amplitude on the HOLD channel to retain the active
agent in the electrode.
5. Set the polarity and amplitude of the current in the EJECT channel.
6. Choose one of two operating methods:
• Leave the hold current on at all times and eect ejection by superimposing
the larger eject current by operating the PRESET/ENABLE switch on the
EJECT channel. The ejection current swamps the smaller hold current. Then,
algebraically adds the hold current to the eject current to compute the actual
ejection current. For example, if the hold current is 5nA subtracted from the
eject current of 50nA, the eective ejection current is 45nA. This method has
the advantage that you only need to operate a single PRESET/ENABLE switch
on the EJECT channel during the experiment.
• Alternatively, simultaneously operate the PRESET/ENABLE switches on both
channels so that the hold current is shut o at the moment the eject current
is applied. In the example above, the eject current would then be +50nA.
AUTO Operation
The timing of current ow from each channel of the Model 260 can be externally
controlled by the use of a pulse generator or computer that can supply a logic level of
at least +5V to the AUTO INPUT terminal. The outer shell of this connector should be
connected to your generator’s ground. It is not connected to the 260 instrument case.

Model 260
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To use the instrument in this way:
1. First place the channel in the AUTO mode.
2. Place the OUTPUT switch in the ENABLE position.
3. Current amplitude and polarity should be preset as described in “Single Channel
Operation” on page 3.
4. Upon application of the +5V command potential to the AUTO INPUT terminal,
the preset current ows from the output terminals for as long as the command
potential is maintained.
NOTE: If the instrument is in the MANUAL mode, the application of the AUTO
INPUT signal halts the current for as long as this command is maintained. This is
the complement of normal AUTO operation.
Compliance Alarms
Each current generator channel contains an audible and visual alarm circuit that is
activated when the current amplitude is large enough to cause the voltage compliance
to be exceeded. In other words, the load resistance is too high for the amount of
current owing. It lets you know that the instrument cannot deliver the amount of
current indicated on the panel ammeter.
The alarm is also triggered if the output path is open-circuited by a loose connection,
air bubble or a blocked micropipette. The initial compliance voltage exceeds 100V but
will decrease proportionately as the battery voltage falls with age.
MAINTENANCE
Battery Replacement
Each channel contains two 9-volt transistor batteries. These should be replaced when
you can no longer get full scale deection of the ammeter as described in “Preliminary
Instrument Check” on page 3. The instrument will continue to operate satisfactorily
for some time after this condition is observed.
1. Turn o the power switch for each channel.
2. Remove the cover of the instrument by unscrewing the four screws, two on each
side, which secure the instrument cover.
3. The batteries are mounted in pairs and are held to the printed circuit board by
a spring clip assembly. Observe the male and female connectors on the battery
mounts, and insert the new batteries so that the connectors mate correctly. Any
9-volt battery will perform satisfactorily, but WPI recommends Duracell 9V alkaline
batteries or their equivalent, because of their superior life expectancy and their
resistance to leakage.

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NOTE: Normal carbon-zinc cells should be replaced when needed or every six
months. Alkaline cells should be replaced when needed or every twelve months.
To avoid potential problems, replace all the batteries at the same time with
batteries of the same brand and lot number.
ACCESSORIES
Part Number Description
EP1 1.0 mm dia. x 3 mm Ag/AgCl Electrode
EP2 12.0 mm dia. x 1 mm Ag/AgCl Electrode
2851 BNC-to-BNC Cable, 6 ‘
504714 Extension Cable, Male banana to Mini-gator, 36”
504715 Extension Cable, Male banana to Mini-clip, 36”
504716 Extension Cable, Male banana to Micro-clip, 36”
SPECIFICATIONS
This unit conforms to the following specications:
Current Range ............................................0 to 100 nanoamperes 0 to 1000 nanoamperes
Maximum Output Voltage (compliance) ...................................................................... 100 volts
Operating Modes..................................................................Manual or Auto (external control)
Auto Input
(external control for current on/o) ................................................................................+5 volts
Auto Input Resistance ..................................................................................1.5 KOhms, approx.
Auto Input Delay ...........................................................................................< 100 microseconds
Output Polarity NORMAL...........................................................................red terminal, positive
Current Meter Error.....................................................................................................+/- 2% max.
Power
Measurement Circuitry .....................................................Four 9V alkaline cells (2/channel)
Measurement Selection...................................................... Wall adapter, 5V DC at 300mA*
*Units manufactured before 2015 did not require the 5V external power supply.
APPENDIX A: APPLICATION NOTES
Current Injection in Microiontophoresis
This applications note addresses itself primarily to electrical circuit considerations and
is a brief introduction to the fundamentals of WPI’s instrumentation for the injection of
ions from glass micropipette electrodes.