World Precision Instruments EVOM2 Instruction Manual
EVOM2
Epithelial Voltohmmeter
Serial No._____________________
Instrumenting scientific ideas
WORLD
PRECISION
INSTRUMENTS
www.wpiinc.com
INSTRUCTION MANUAL
082318
EVOM2
CONTENTS
ABOUT THIS MANUAL ................................................................................................................... 1
INTRODUCTION .............................................................................................................................. 1
QUICK REFERENCE ......................................................................................................................... 2
For Resistance Measurements: ....................................................................................... 2
For Voltage Measurements:.............................................................................................. 2
INSTRUMENT DESCRIPTION ........................................................................................................ 2
Parts List ...................................................................................................................................... 2
Unpacking ................................................................................................................................... 3
Set-up ........................................................................................................................................... 3
Test Resistor ......................................................................................................................... 3
STX2 Electrode ..................................................................................................................... 3
Meter ...................................................................................................................................... 3
Instrument Diagnostics .......................................................................................................... 5
Testing the EVOM2 Meter ................................................................................................. 5
OPERATING INSTRUCTIONS ....................................................................................................... 5
Positioning Electrode in a Culture Cup ................................................................................ 5
Making Resistance Measurements ....................................................................................... 7
Making Voltage Measurements ............................................................................................. 7
MAINTENANCE ................................................................................................................................ 8
Cleaning the STX2 Electrode .................................................................................................. 8
Disinfecting the STX Electrode ............................................................................................... 9
Sterilizing the STX2 Electrode ................................................................................................ 9
Resurfacing the Electrode .....................................................................................................10
Storing of the Electrode ........................................................................................................10
EVOM2 Charger and Battery ................................................................................................ 10
Changing the Battery Pack ....................................................................................................11
ACCESSORIES.................................................................................................................................13
TROUBLESHOOTING ...................................................................................................................14
EVOM2 Meter ...........................................................................................................................14
STX2 Electrode ......................................................................................................................... 14
SPECIFICATIONS ............................................................................................................................ 18
APPENDIX A: RESISTANCE CALCULATIONS ............................................................................ 18
Resistance ................................................................................................................................. 18
Resistance Value of the “Blank” Insert ...............................................................................19
Unit Area Resistance .............................................................................................................. 19
APPENDIX B: 24 MM DIAMETER (6-WELL) INSERTS AND STX ELECTRODES ................ 20
APPENDIX C: IMPROVING THE ACCURACY AND REPEATABILITY OF THE SYSTEM ...... 20
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.
DECLARATION OF CONFORMITY .............................................................................................. 22
WARRANTY .....................................................................................................................................23
Claims and Returns ................................................................................................................23
EVOM2
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 EVOM2 measures resistance or voltage across a tissue membrane.
INTRODUCTION
EVOM was the rst instrument designed to perform routine Trans Epithelial Electrical
Resistance (TEER) measurement in tissue culture research. EVOM2 is the next
generation. The conuence of the cellular monolayer is determined by an increase in
TEER detected using the unique electronic circuit of the EVOM2 and STX2 electrode
(included with the instrument). The EVOM2 qualitatively measures cell monolayer
health and quantitatively measures cell conuence. When combined with WPI’s
Endohm chamber, the EVOM2 can also be used to perform trans endothelial electrical
resistance measurement.
The EVOM2 produces an AC current that avoids electrode metal deposits and adverse
eects on tissues, which can otherwise be caused by a DC current. In addition,
resistance readings are unaected by membrane capacitance and membrane voltage.
EVOM2 is designed with an internal rechargeable 6V NiMH 2700mAH battery pack.
The unit is supplied with an external battery charger. A fully-charged battery pack will
provide about eight hours of running time. When the battery power falls below the
nominal threshold, the meter automatically powers o. While the meter operates
safely when it is plugged into an AC power source, WPI recommends disconnecting
the meter from the charger when it is in use. Doing so provides for the maximum
electrical isolation and reduces the noise to ensure readings of the highest accuracy.
2 WORLD PRECISION INSTRUMENTS
For automation of TEER measurement, consider WPI’s REMS AutoSampler (WPI
# REMS), which includes the robotic sampler, data acquisition board, base plate,
Windows
®
based software and an electrode for either the 24- or 96-well plate.
QUICK REFERENCE
For complete instructions on performing measurements with the EVOM2, see
"OPERATING INSTRUCTIONS" on page 5
For Resistance Measurements:
1. Disconnect the EVOM2 from the charge and turn the Power on (I).
2. Sterilize the electrode.
3. Connect the electrode to the meter.
4. Precondition the electrode in growth media.
5. Set the Function switch to Ohms.
6. Measure the blank resistance and record the value.
7. Perform the measurements. To obtain the actual tissue reading, subtract the
blank resistance value.
8. Clean, dry and store the electrode.
For Voltage Measurements:
1. Sterilize the electrode.
2. Connect the electrodes to the EVOM2 and leave the power o.
3. Equilibrate the electrode in growth media with the EVOM2 power o and the
Function switch set to Ohms.
NOTE: Electrode tips must be immersed in solution to equilibrate.
4. Disconnect the EVOM2 from the charger and set the Function switch to Millivolts.
5. Turn the Power on (I).
6. Measure the blank voltage and record the value.
7. Make your voltage measurements across the membranes you are testing. To
obtain the actual tissue reading, subtract the blank voltage value.
8. Clean, dry and store the electrode.
INSTRUMENT DESCRIPTION
Parts List
(1) EVOM2 meter
(1) STX2 electrode set
(1) 91750 1000W test resistor
(1) 600-grade ultra-ne sandpaper
(1) A/C power cord and charger
(1) Instruction Manual
EVOM2
WORLD PRECISION INSTRUMENTS 3
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 loss or damage should be
reported at once to the carrier and an inspection requested. Please read the section
entitled “Claims and Returns” on page 23 of this manual. Please call WPI Customer
Service if any parts are missing.
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 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. Please read the section
entitled “Claims and Returns” on page 23 of this manual.
Set-up
Test Resistor
The 1000W test resistor (WPI #91750) is shown in Fig. 2. See
"Testing the EVOM2 Meter" on page 5 for instructions on using the test resistor.
Fig. 2–1000W Test resistor
STX2 Electrode
For resistance measurements only, the STX2 electrode can be used
directly from dry storage without preconditioning. The STX2
electrode (Fig. 3) incorporates a xed pair of probes, 4mm wide
and 1mm thick. Each probe has an outer and an inner electrode.
(See Fig. 4 on page 4) The outside electrodes are small silver
(Ag) pads that pass current through the membrane sample. They
are referred to as current electrodes. The inner electrodes are
small Ag/AgCl pellet voltage sensors. They are referred to as
voltage electrodes.
Fig. 3–(Right) STX2 electrode
Meter
The EVOM2 is ready to use, but you will need a slot-head screwdriver (not included) to
calibrate the R ADJ screw.
4 WORLD PRECISION INSTRUMENTS
CAUTION: Do not leave the meter in direct sunlight for extended periods of
time. The LCD display will become dark and unreadable.
Labeled items on Fig. 3 are described below.
1
Digital LCD Display
4 Analog Output
3
Function Switch
2
Power Switch
5 R ADJ Calibration
6 Input Port
7 Charger Input Jack
Fig. 4–EVOM2 meter
Digital LCD Display: The Digital LCD Display registers readings of four and a
half digits. When the meter is measuring voltage, it displays the potential dierence
between the two electrodes in millivolts (mV) up to 199.9mV. When the meter is
measuring resistance, it displays the resistance between the two electrode probes
in ohms (W). Although the meter will provide readings up to 13,000W, the accuracy
specication is only guaranteed up to 10,000W.
Power Switch I/O: The toggle switch turns the meter on (I) and o (O).
Function Switch (Ohms/Millivolts): When in the Ohms position, the meter is in
the resistance measuring mode. When in the Millivolts position, the meter is in the
voltage measuring mode.
Analog Output: This standard BNC connection allows for output of analog data to
a recording device.
R ADJ Calibration Screw: When the 1000W test resistor is inserted into the input port,
this screw is used to calibrate the meter display to 1000W while in the Ohms mode.
Input Port: Insert the RJ-11 plug of the test resistor, STX2, STX3 or Endohm into
this port to connect it to the meter.
Charger Input Jack: Insert the charger connector into the Charger Jack and plug
the other end into a standard wall outlet to charge the EVOM2 battery pack. Do NOT
take resistance or voltage measurement with the charger connected.
EVOM2
WORLD PRECISION INSTRUMENTS 5
Instrument Diagnostics
It is recommended that EVOM2 be put through the diagnostics described below
before using it for the rst time and then periodically thereafter. If there is a concern
that the meter or the electrode is not functioning properly, the following protocols
may be used to conrm EVOM2’s operating status.
Testing the EVOM2 Meter
1. Insert the RJ-11 plug at the end of the test resistor (Fig. 2) into the Input port on
the meter.
2. Set the Function Switch to Ohms.
3. Disconnect the EVOM2 from the charger and turn the Power on (I). The meter
should display 1000W. If not, adjust the R ADJ screw with a small slot-head screwdriver until the meter shows a reading of 1000W.
OPERATING INSTRUCTIONS
Before making any measurements, charge the EVOM2 overnight. Allow the unit to
warm up for 20 minutes before making any measurements.
Positioning Electrode in a Culture Cup
Proper placement of the electrode in the cell is critical to making accurate
measurements. The STX2 electrode is designed to facilitate measurements of
membrane voltage and resistance of cultured epithelia in tissue culture wells. The
lengths of the electrodes are unequal allowing the longer (external) electrode to
touch the bottom of the dish containing the external culture media while preventing
the shorter (internal electrode) from reaching the bottom of the tissue culture cup
or insert (see Fig. 5). This feature ensures proper positioning between the electrode
and the cell layer in the cup during the trans membrane measurement. In addition,
by positioning the longer tip so that it touches the bottom of the dish each time, the
reproducibility of the measurements is signicantly improved.
Fig. 5–Electrodes in solution
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