WPI 900A User manual
Instrumenting scientific ideas
WORLD
PRECISION
INSTRUMENTS
900A
Micropressure System
Serial No._____________________
www.wpiinc.com
INSTRUCTION MANUAL
071618
900A Micropressure System
World Precision Instruments i
Copyright © 2018 by World Precision Instruments. 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
Notes and Warnings................................................................................................................. 1
Parts List...................................................................................................................................... 2
Other Required Items (not included)................................................................................... 3
Unpacking................................................................................................................................... 3
INSTRUMENT DESCRIPTION ........................................................................................................ 4
System Overview....................................................................................................................... 4
Response Rate .................................................................................................................... 5
Using Sensitivity and Damping to Correct Oscillations.............................................. 5
Circuit Discussion................................................................................................................ 6
Getting Started .......................................................................................................................... 7
Pressure and Vacuum Supply .......................................................................................... 7
Microelectrodes................................................................................................................... 7
Salt Solutions........................................................................................................................ 8
Experimental Containers................................................................................................... 9
Micromanipulators.............................................................................................................. 9
Viewing and Imaging .......................................................................................................... 9
Alarm ....................................................................................................................................10
Liquid Trap ..........................................................................................................................10
OPERATING INSTRUCTIONS.......................................................................................................11
Setting Up and Powering the 900A...............................................................................11
Zero Adjusting the Pressure Pod to Ambient Pressure...........................................12
Applying Pressure and Vacuum and Re-zeroing .......................................................12
Seting Up the Measurement Site ..................................................................................14
Preparing the Microelctrode and Microelectrode Holder ......................................14
Adjusting Electrode Resistance......................................................................................18
Connecting the Pressure Pod to the Microelectrode Assembly ...........................19
Preparing the Microelectrode for Operation Mode .................................................19
Adjusting the Sensitivity and Damping ........................................................................21
Calibrating the Pressure Signal......................................................................................22
Moving the System to the Recording Site ...................................................................23
Setting Pressure Mode ....................................................................................................25
Measuring DC Potential...................................................................................................26
Adjusting the 900A Pressure Transducer ...................................................................26
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MAINTENANCE ..............................................................................................................................27
Cleaning.....................................................................................................................................27
Replacing the Fuse..................................................................................................................27
Service........................................................................................................................................27
ACCESSORIES.................................................................................................................................28
SPECIFICATIONS............................................................................................................................29
DECLARATION OF CONFORMITY ..............................................................................................30
WARRANTY .....................................................................................................................................31
Claims and Returns ................................................................................................................31
Repairs.......................................................................................................................................31
900A Micropressure System
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—The 900A is a micropressure system.
INTRODUCTION
WPI’s model 900A micropressure system is designed to measure pressures from
cavities. The micropressure system includes a main electronic Control Unit, Probe
an outside diameter of 2–5µm act as microelectrodes when paired with the 900A
sensing probe to complete a circuit across the measurement location. A pressure
source supplying up to +500mmHg of pressure and a vacuum source supplying up to
–300mmHg vacuum interfaces through the Pressure Pod to maintain a null pressure,
that is proportional to the pressure sensed at the tip of the microelectrode.
Notes and Warnings
NOTE: Use fresh micropipettes each time it is to be used.
NOTE: Be sure the air pressure source provides clean, dry air.
NOTE: Use micropipettes with tips pulled to 2 to 5µm in diameter.
NOTE
Pressure Pod tubing port.
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CAUTION: Always pay attention to the tube between the holder and the
to the Zero Set mode. Disconnect the tube, and use the air pressure supply to
blow the solution drops out. Leaving solution in the pressure tube may damage the
Pressure Pod.
!
CAUTION: It is important that the pressure and vacuum sources supply clean,
damage of this sort is not covered under warranty.
!CAUTION: If the microelectrode is connected to the Pressure Pod before the
pushed through the Fluid Trap and into the Pressure Pod causing damage to
the piezo valve. This damage is not covered under warranty.
!CAUTION:Before moving the micropipette from one recording site to
another, set the Loop Status switch to Zero Set. This ensures that no
pressure is applied to the micropipette while it is being moved. If this is not
done, the pressure pod tries to compensate the increased tip resistance (caused by
solution from the micropipette.
Parts List
After unpacking, verify that there is no visible damage to the sensor. Verify that all
items are included:
Each 900A system includes the following components:
(1) 900A Micropressure System Control Unit with power cord
(1) 900AP Probe
(1) 900APP100 Pressure Pod or 900APP Pressure Pod
(1) 900A Startup Kit, which includes:
(12) 13157 Female Luer Fittings, 3/32” polypropylene
(12) 13161 Male Luer Fittings, 3/32” polypropylene
(12) Male Luer Lock Adapter Fittings, 1/16” polypropylene
(3) 14061 Dead-Ender for Male or Female Luer Plug, Non-Vented
(1) MEH Probe Holder
(3) 3742 Female Tee Luer Fittings
(3) 10 cc syringes without needles
(1) 15 ft. 5/32” Polyurethane Tubing
(1) 900A Vacuum Fluid Trap Assembly
900A Micropressure System
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(1) CAL900A Pressure Calibration Chamber
(2) MEH6RF10 Microelectrode Holder with Pellet, 1.0 mm
(2) MEH6SF10 Microelectrode Holder with Pellet, 1.0 mm
(1) MF28G-5 MicroFil, 28 guage, 97 mm long
(1) RC1T Silver/Silver Cloride Reference Electrode
(10) TIPTW900A Pre-Pulled µTip Micropipettes, 1.5–2.0 µm ID (See
“Microelectrodes” on page 7)
(2) 13776 Adapters, Reference Electrode to Ground Jack, 2 mm
(1) Potentiometer Tweeker
(1) Instruction Manual
Other Required Items (not included)
Other required items (not included):
(1) Manometer:
• WPI # SYS-PM01D (1 psi)
• WPI # SYS-PM01R (1 psi) Rechargeable
• WPI # SYS-PM015D (15 psi)
• WPI # SYS-PM015R (15 psi), Rechargeable
• WPI # SYS-PM100D (100 psi)
• WPI # SYS-PM100R (100 psi), Rechargeable
(1) Voltage recorder (oscilloscope or data acquisition system)
Pressure and vacuum source (See “Pressure and Vacuum Supply” on page 7)
Salt solutions
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 31 of this manual. Please contact WPI Customer
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 31 of
this manual.
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INSTRUMENT DESCRIPTION
System Overview
Control Unit
Pressure
Pod
Probe Trap
Fig. 2—The 900A system includes the control unit, pressure pod, probe and trap.
The 900A uses an ion gradient at the tip of sensing electrode to measure
pressure. The internal pressure of the microelectrode is continuously monitored
and adjusted to equal the pressure outside the tip, to keep the ionic gradient in
dynamic equilibrium. The dynamic equilibrium of the ion concentration at the tip
of the microelectrode is continuously maintained as part of a loop circuit formed
serves as an electrical feedback loop that is monitored for deviations. Once the
microelectrode. The 900A senses the ionic alteration caused by the pressure change.
The 900A then signals the Pressure Pod to maintain the circuit to the equilibrium (null)
value.
Within the Pressure Pod, a piezoelectric gas valve actively regulates vacuum and
pressurized air in and out of the Pressure Pod. The pressure of the incoming air is
greater than the vacuum, creating a net positive pressure when the piezoelectric
valve is open. The piezoelectric gas valve within the Pressure Pod is continuously
equilibrium in the microelectrode, the Pressure Pod promptly reacts to supply an
opposing pressure that adjusts the circuit back to its null value. The amount of
pressure required by the Pressure Pod to maintain equilibrium of the circuit is equal
to the pressure outside the tip of the microelectrode. This applied pressure is sensed
by a pressure transducer within the Pressure Pod and is digitally displayed on the
900A’s front panel. A voltage signal proportional to the displayed pressure reading is
simultaneously sent to the Pressure Signal output connector that can be connected to
a recording device, such as an oscilloscope or other data acquisition system.
900A Micropressure System
World Precision Instruments 5
Response Rate
pressure transducer piezoelectric valve outlet, due to the compressibility of air. Long
lengths of tubing add dead space, which slows overall system response. Keeping the
residual volume low by mounting the Pressure Pod close to the microelectrode and
using short lengths of small-bore tubing minimizes dead space and contributes to a
rapid system response.
Using Sensitivity and Damping to Correct Oscillations
All feedback control systems tend to become unstable and oscillate under certain
conditions. The 900A provides two controls for combatting instability and oscillation—
Sensitivity and Damping. Decreasing Sensitivity or increasing Damping often
reduces or stops oscillations. The proper settings for both controls depends on the
particular application.
Keep the Sensitivity knob as high as possible to provide close matching and following
of the external pressure by the internal pressure in the micropipette. We recommend
starting at the 12:00 position, then adjusting in a counterclockwise direction, as
needed. Generally, to maintain proper response, Sensitivity should not be set below
one-third of the full rotation.
The Damping knob adjusts the amplitude of feedback. Turning the damping control
clockwise reduces the amplitude of the feedback. Turning the damping control
counter-clockwise increases the amplitude of the feedback. Starting at the 12:00
position, one-quarter to one -third rotation typically produces a stable, quiet baseline.
6 World Precision Instruments
Circuit Discussion
The 900A
pressure transducer and Pressure Pod.
Fig. 3—(Right) The circuit is complete when
the reference electrode is immersed in the
solution at the measurement site, along with
the microelectrode, and both the probe and the
reference electrode are properly connected to the
900A system.
OSCILLATOR: A Wein bridge oscillator generates
a 1000 Hz sinusoidal voltage. This is amplitude
stabilized by internal negative feedback
transistors in the bridge circuit.
HEAD STAGE (or FOLLOWER): A 1000 Hz
carrier constant current is injected through the
microelectrode. The resulting voltage drop is
compensated in the follower circuit by advancing
the Electrode Resistance dial so that balance
null is achieved. The microelectrode resistance
microelectrode resistance changes, a 1000 Hz
phase detector.
PHASE DETECTOR: This is a synchronously
switched detector in a single integrated circuit
BUFFER AMPLIFIER
Pod driver. It compensates the detector signal with output from the pressure
transducer in order to compensate for the inherent lag in propagating the pressure
changes transmitted to the micropipette tip. The lag would normally cause the system
•
counter clockwise) causes the system to oscillate at higher frequencies.
• Too much damping (For example, the Damping knob is turned too
far clockwise) can result in a slow rate of response and low frequency
oscillations.
PRESSURE TRANSDUCER: The pressure transducer is a silicone strain gauge
resistance bridge device. Its volume and pressure displacement are small, and its
meter. The meter has a resolution of 0.1 mmHg from +199.9 to –199.9 mmHg. (The
900APP100 is capable of measuring ±100 mmHg.) Pressures outside this range can
900A Micropressure System
World Precision Instruments 7
be viewed by toggling the Range switch to High. The pressure output can also be
monitored via the BNC connector marked Output on the front panel. The output level
of this signal is 10 mV/mmHg.
PRESSURE POD: The pressure pod consists of a driver circuit to operate the
piezoelectric controller and an alarm circuit to warn when the maximum pressure of
the controller has been reached.
Getting Started
Pressure and Vacuum Supply
The maximum pressure that should be applied to the pressure pod is +500 mmHg.
The maximum recommended vacuum is –300 mmHg. In the Auto mode, the system
pressure changes may cause a pressure reading error. For accurate pressure change
readings, both pressure and vacuum sources should be stable.
If your experiment involves pressure measurements consistently lower than the rated
maximum, you can use lower supply pressure and vacuum. For example, if pressure
readings at the pressure measuring site are fairly consistent and slow-changing at
approximately 150 to 200 mmHg, a positive supply pressure of +300 mmHg would
250 mmHg and vacuum of -60 will be ideal.
To keep the pressure gradient high and ensure a quick, accurate response, plan to
provide positive/negative pressures at least 50 mmHg greater that the maximum
considerably.
!
CAUTION: It is important that the pressure and vacuum sources supply clean,
damage of this sort is not covered under warranty.
Microelectrodes
900A’s response. Shorter
tipped microelectrodes that do not have an excessively long taper (similar to a
patch clamp tip) work best. Microelectrodes with internal tip diameters of 2-5µm are
suggested (WPI #TIPTW900A). Within this size range, the microelectrodes will operate
within the normal parameters described here. Pipettes can be pulled from glass
PUL-1000). Tip size can be estimated based on the resistance value measured on the
Electrode Resistance dial.
TIP
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Salt Solutions
Prepare salt solutions before you begin. To measure a change in resistance, the 900A
relies on a steep concentration gradient. This gradient should approximate a 10×
should be 0.1 M NaCl. NaCl is a common choice for 900A users. KCl has been used
well in this system, though it should be noted that KCl is a well-known agent used
to stop the heart. You may alternately choose to utilize a K-free physiological saline,
+
-free PBS works well with a 10× solution in the
microelectrode and 1× solution in the electrolyte bath. (See recipe below). Traditional
PBS with K
+
is suitable for live cells in culture. Other physiological salines also contain a
similar osmolality of electrolytes and can also be well-utilized.
TIP
: Alcian blue can be added to the microelectrode solution to add a blue tint.
Alcian blue is conductive and in small amounts can add excellent contrast to the
microelectrode for enhanced viewing. Microelectrode solution should not contact
measurement sites. Other solutions will also work well, if the ionic gradient is
maintained. Appropriate physiological solutions for experimental scenarios should be
determined experimentally to suit the physiology of the organism or recording site,
when appropriate.
When working within physiological conditions, it is advantageous to shift the
concentration gradient inside the pipette tip such that the tip contains a solution that
concentration electrolyte bath solution and the outside of the top. This will also create
rate of response to externally-applied stepped pressure, but this is not perceptible in
most applications.
Recipe for 10× K+-free Phosphate Buered Saline
Mass (g) Chemical
75.97 NaCl
12.46 Na2HPO4
4.8 NaH2PO4
1. Add chemicals to a 1 L container with 850 mL double distilled H20.
2. Stir until dissolved.
3. Adjust pH to desired value.
4. Add enough water (QS) to bring the quantity to 1L.
5. Dilute 1:10 to create electrolyte bath solution that will be close to 290 mOsm.
!CAUTION: High concentration salt solutions will evaporate and crystalize
quickly and can damage the glass microelectrode tip.
900A Micropressure System
World Precision Instruments 9
WARNING: Potassium will stop the heart.
Experimental Containers
A sturdy container (petri dish) of adequate depth will be able to hold an appropriate
depth of electrolyte bath solution and accomodate the experimental subject. 2-3%
covered with electrolyte bath with the reference ground electrode secured within
or over the agarose. Z-molds (WPI #Z-MOLDS)
in the agarose that greatly help when stabilizing organisms or other vessels. The
depressions can also allow for conductivity between the microelectrode and the
reference electrode so a shallow layer of electrolyte bath can be used.
Fig. 4—Z-MOLDS come in four dierent patterns. Press into freshly poured agarose and
allow the agarose to solidify. Remove the mold. The impressions make it easy to hold
embryos.
Micromanipulators
A micromanipulator is required to hold the Probe and microelectrode. Though the
probe could conceivably be moved into the recording site by hand, it is unlikely that
with a micromanipulator.
!
CAUTION: The experimental platform should be stable. Micromanipulators
and measurement sites need to be static and secure. Small movements
Viewing and Imaging
A stereo microscope is suggested for viewing the movement of the microelectrode
as it penetrates into the experimental subject. As the microelectrode begins to
10 World Precision Instruments
penetrate, the circuit is broken if the tip of the microelectrode becomes blocked by
tissue or other barricades. This can cause an alarm in the circuit (See “Alarm” on page
into the Pressure Pod. Fluid in the Pressure Pod will damage the servoelectric
valve. It is further important to monitor the progress of the microelectrode to know
when the microelectrode is within the recording site. An imaging system is also
advantageous to monitor variation between experimental subjects and for monitoring
and recording of timed experiments.
Alarm
The 900A alarm sounds:
• When the Pressure Pod valve is completely open to indicate that maximum
pressure has been reached.
• When electrical continuity is broken for any reason. For example, if the
the Ag/AgCl pellet, the ground reference is disconnected, etc. or the tip is blocked,
or if the sensitivity is adjusted too high.
It is crucial that you respond to alarms immediately. In each scenario, the
Pressure Pod.
Quick response to the alarm prevents this damage from occurring. When an alarm
sounds, return the 900A to the Zero Set position. This will bring the system out of
dynamic operation and into a “safe mode.” See “Operating Instructions” on page 11
for more information.
Liquid Trap
A Liquid Trap is provided with the 900A and should be installed between the
micropipette holder and the 900A Pressure Pod to prevent intrusion of liquid into the
Pressure Pod.
900A Micropressure System
World Precision Instruments 11
OPERATING INSTRUCTIONS
Probe Connection Port
Circuit Ground
Chassis Ground
Ground Strap
Loop Status Switch
Damping Knob
Sensitivity Knob
Electrode Resistance Dial
Follower Adjustment & Output Port
Data Acquisition Port
Pressure Pod Port
Pressure Set Switch & Dial
Offset Switch and Dial
Data Acquisition System
Null Detector
Meter
Power Switch
Fig. 5—Refer to this diagram when setting up the 900A micropressure system. Be sure the
setup is complete before you turn on the power.
Setting Up and Powering the 900A
1. Line up the pins and connect the seven-pin cable on the Pressure Pod to the
connector labeled Pressure Pod on the right side of the front panel of the 900A.
2. Connect the 900A Probe to the connector labeled Probe on the left side of the
front panel of the 900A.
3. Connect the tip of the 900A Probe to CKT and CHAS ground connections using a
banana to 2 mm pin adapter (WPI #13776).
NOTE: The CKT and CHAS (circuit and chassis) ground connections should be
electrcally connected with a metal strap, so either ground connection is suitable.
4. Connect the power cord to the receptacle on the rear panel of the 900A. Plug the
other end into a wall socket.
5. Connect the reference electrode from the CAL900A or the experiment to the
ground terminal marked CKT (or CHAS) on the front panel of the 900A.
6. Place the Loop Status switch in the Zero Set position. This maintains a pressure
7. Set the Damping and Sensitivity control knobs to the 12:00 position.
8. Set the Electrode Resistance dial fully counterclockwise to zero.
12 World Precision Instruments
9. Set the Oset switch to the O position.
10. Set the Pressure switch to O position.
11. Turn the power switch on and let the system warm up for 15 minutes.
12.
Using a BNC cable, connect the data acquisition port marked Pressure Signal on
the right side of the 900A front panel to an oscilloscope or data acquisition system.
Zero Adjusting the Pressure Pod to Ambient Pressure
1. Verify that the Loop Status is set to Zero Set and the system has warmed up for
at least 15 minutes.
2. In the Zero Set mode, applying no pressure or vacuum to the Pressure Pod,
insert a screwdriver into the recess on the Pressure Pod marked XDCR Zero
and turn clockwise or counterclockwise until the digital meter on the 900A reads
Fig. 6—Using a small screwdriver, adjust the XDCR Zero until the meter reads zero.
Applying Pressure and Vacuum and Re-zeroing
1. Verify that the Loop Status switch is set to Zero Set.
2. Use a pressure manometer to regulate the source of pressure and vacuum
for the 900A Pressure Pod to the desired pressure (e.g. +350 mmHg for the
pressure, and –150 mmHg for the vacuum.) If you are using a the WPI #PM015
Pressure Manometer to monitor the pressure, use port B on the meter for
measurement.
!CAUTION: Do not connect the pressure or vacuum until you are sure the
values are within the safe pressure ranges for the pod. The maximum pressure
is 500 mmHg and the maximum vacuum is –300 mHg. Pressures outside of
the safe operating pressure or vacuum can damage the Pressure Pod. This sort of
damage is not covered under warranty.
900A Micropressure System
World Precision Instruments 13
NOTE: The pressure and vacuum sources may be regulated to pressures other
than those suggested here, however, IT IS CRUCIAL THAT THE PRESSURE SIDE
ALWAYS BE OF A GREATER ABSOLUTE VALUE THAN THE VACUUM SIDE, AND
THAT THERE IS A MINIMUM OF 75 mmHg DIFFERENCE BETWEEN THE PRESSURE
AND VACUUM SOURCES.
3. Connect these regulated pressure and vacuum sources to their respective input
ports on the Pressure Pod.
4. Block the To Micropipette
Fig. 7—Use your nger to block the To Micropipette port on the top of the Pressure Pod.
Fig. 8—Use a screwdriver to adjust the recessed Pressure screw until the meter reads zero.
5. Keeping the To Micropipette port blocked, insert a screwdriver into the
recess marked Pressure on the 900A front panel, and turn clockwise or
counterclockwise until the digital meter reads 0 mmHg. (Fig. 8)
should remain at 0 mmHg. If the unit has been properly re-zeroed, very little
change occurs when the tubing port is opened.
Fig. 9—Remove your nger to open the To Micropipette pressure port.
NOTE900A, disconnect the
pressure and vacuum supplies and repeat the previous steps in this section.
14 World Precision Instruments
Seting Up the Measurement Site
NOTE: It is advantageous if the following steps are completed using the CAL900A as
your test measurement site. The CAL900A creates a stable platform to test the system
and calibrate the voltage output signal to known pressures for data recording. This
accessory is sold separately. If you are not using the CAL900A, a petri dish is perfectly
adequate to prepare the system as described below. The following directions assume
you are using the CAL900A.
1. Prepare the two electrolyte solutions:
• Microelectrode Solution (e.g. NaCl)
• Electrolyte Bath Solution (e.g. NaCl)
2. Put the Electrolyte Bath Solution into the CAL900A Pressure Calibration
Chamber. The level should be enough to cover the Ag/AgCl pellet in the CAL900A.
3. Connect the integrated blue ground (Ag/AgCl pellet) connection of the CAL900A
to the CKT or CHAS ground connection on the 900A using a banana to 2 mm pin
adapter (WPI #13776).
NOTE: The CKT and CHAS ground connections are electrically connected with a metal
strap, so either ground connection is suitable.
TIP: Connecting the CAL900A to the ground on the 900A will allow a completed
circuit when the microelectrode is inserted in the CAL900A chamber. As such, the
integrated Ag/AgCl electrode in the CAL900A now serves as the reference electrode,
for testing the system. If you are NOT using the CAL900A
Electrolyte Bath Solution, and immerse a dry Ag/AgCl reference electrode. Connect the
reference electrode to the 900A through the CKT or CHAS ground connection, as with
the CAL900A.
Preparing the Microelctrode and Microelectrode Holder
REMINDER: Use a micropipette pulled to a tip diameter of 2–5 µm. A high
concentration microelectrode solution is important in order to maintain a large
concentration gradient between the microelectrode’s internal salt solution and the
solution outside the tip.
1.
solution and allowing the solution to wick up into the tip of
the micropipette. This decreases the possibilities of air
bubbles. Ideally, the pipette tip should be set into solution
for several hours or longer prior to operation.
TIP: Utilize an electrode storage receptacle (WPI #E210) to
Fig. 10—(Right) The E210 storage jar is perfect for safely storing
your pulled micropipettes. You can even ll the jar with your lling
solution so you can immerse the tips prior to the study.
900A Micropressure System
World Precision Instruments 15
MicroFilMF28G67-5) are ideally suited
for this application. Do not allow air bubbles to remain in the pipette.
Fig. 11—Attach the MicroFil to a syringe lled with with solution. Insert the MicroFil into
the micropipette all the way to the tip. Begin lling the micropipette and slowly draw the
MicroFil out of the micropipette as the uid lls the micropipette.
NOTE
microelectrode.
!CAUTION: Protect the microelectrode tip from damage. Limit exposure of the
cause salt crystals to form in and around the tip. This can damage the tip of
the micropipette. It is recommended that the tip be immersed in the microelectrode
solution (i.e. in an electrode storage jar) prior to inserting into the electrode holder.
Once the microelectrode is connected to the microelectrode holder, the tip should
likewise remain immersed in solution whenever possible to prevent the formation of
salt crystals and damage to the glass.
3. Fill the microelectrode holder, making sure that no air bubbles remain in the
microelectrode holder.
Fig. 12—Use MicroFil to ll the microelectrode holder with solution.
16 World Precision Instruments
4. Insert the microelectrode into the microelectrode holder and tighten the cap.
Fig. 13—Press the glass micropipette into the electrode holder.
5. Check again to be sure that no air bubbles remain in the microelectrode or the
microelectrode holder. Tightening the cap can expose any otherwise unseen
Fig. 14—Here you can clearly see a bubble trapped in the microelectrode holder.
NOTE
microelectrode holder to complete the circuit.
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