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WPI EVOM Скачать руководство пользователя страница 26

Improving the Accuracy and Repeatability of the System

For measuring low-resistance tissue culture, or for more precise measurement, the user
should consider using the

Endohm

chamber instead of

STX2

electrode. Although cells

must be transferred from their culture wells to the Endohm chamber for measurement,
more accurate measurement of membrane resistance can be achieved. By introducing
concentric pairs of electrodes above and beneath the membrane, the

Endohm

reduces

background resistance (with a blank cup inserted) from 150

Ω

to less than 5

Ω

(except

Endohm-6

, which is higher). The shape of the current electrodes allows a more

uniform current density to flow across the membrane. With fixed electrode geometry,
the variation of readings on the same sample is 1-2

Ω

as compared to 5-10% of the

total reading using the

STX2

electrodes. The

Endohm

, together with the

EVOM

, offer

the most accurate, convenient and economical solution for trans membrane electrical
resistance measurement.

22 WORLD PRECISION INSTRUMENTS

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Содержание EVOM

Страница 1: ...EVOM EVOMX Epithelial Voltohmmeters World Precision Instruments INSTRUCTION MANUAL Serial No _____________________ 021308 www wpiinc com ...

Страница 2: ......

Страница 3: ...STX2 electrode preparation 7 3 Placement of the electrode in the sample cup 7 4 Measuring Resistance 9 5 Measuring Voltage 10 INSTRUMENT MAINTENANCE 10 Electrodes 10 EVOM Meter 12 ACCESSORIES 13 TROUBLESHOOTING 15 SPECIFICATIONS 19 APPENDIX A SUMMARY OF OPERATING INSTRUCTIONS 20 APPENDIX B IMPORTANT APPLICATION NOTES 21 Resistance value of the blank insert 21 Special Note 24 mm diameter 6 well ins...

Страница 4: ......

Страница 5: ...AC current that avoids electrode metal deposits and adverse effects on tissues which can otherwise be caused by a DC current In addition resistance readings are unaffected by membrane capacitance and membrane voltage A modified version of the EVOM the EVOMX has been adapted for multi well testing by replacing the momentary R resistance measurement pushbutton with a toggle switch allowing constant ...

Страница 6: ... RMA required and instructions from our 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 100 mm four inches of shock absorbing material Pl...

Страница 7: ... resistance measurement function is performing acceptably During the test the external electrode is disconnected from the meter by the switch Therefore the electrode does not need to be connected to the meter during the test In model EVOMX the Measure R pushbutton see below has been replaced by a toggle switch The toggle switch must be in the off position when this test is performed 5 Measure R Pu...

Страница 8: ...de to the meter 9 Digital LCD Display The Digital LCD Display registers readings up to 4 digits depending on the scale used When the meter is measuring voltage it displays the potential difference between the two electrodes in millivolts mV up to 199 9 mV When the meter is measuring resistance it displays the resistance between the two electrode probes in Ω with range switch set to 2000 Ω or KΩ wi...

Страница 9: ... Turn the Power Switch on 3 Press the TEST R button NOTE Do not press the TEST button when taking measurements or you may obtain a false resistance measurement The meter should read as follows Range Switch Position Display Reading 2000Ω 1000 Ω 10 Ω 1 20 KΩ 1 kΩ If the meter does not show these values consult the Troubleshooting section in this manual TESTING THE ELECTRODE FOR RESISTANCE MEASUREMEN...

Страница 10: ...n error Instrument battery failure TESTING THE ELECTRODE FOR VOLTAGE MEASUREMENTS 1 Equilibrate the electrode as instructed in the Electrode Preparation section under OPERATING INSTRUCTIONS 2 Immerse the electrode tips in an electrolyte solution similar to the experimental culture medium or in 0 1 0 15 M KCl or NaCl 3 Turn the Mode Switch to V 4 Turn the Power on 5 The digital panel meter may read...

Страница 11: ...ircuited for several hours the asymmetrical potential difference across the two voltage electrodes is reduced The inter electrode DC potential will be a few millivolts or less and quite stable Table 1 lists the recommended equilibration time before using the electrode Sterilize the electrodes if desired See section on Sterilization under Instrument Maintenance Table 1 STX2 Electrode Equilibration ...

Страница 12: ...er from exposure to distilled water during which time the potential may drift by a few millivolts If it is necessary to wash the electrodes between measurements to avoid carryover of one sample into the next the electrodes should be rinsed with the experimental culture media NOTE Transwell inserts made by Corning Costar in general have a greater distance between the bottom of the filter cup and th...

Страница 13: ...ically the product of the resistance and the area is calculated and reported This value is independent of the area of the membrane used NOTE Resistance readings for 24 mm or larger diameter inserts obtained using the EVOM with the STX2 electrode should not be converted to unit area resistance See additional discussion of this point in APPENDIX B Special Note 24 mm diameter 6 well inserts and the S...

Страница 14: ... Set 2101 One standard 9V battery ANSI 1604A 3569 Six standard 1 5V AA batteries ANSI 15A Electrodes Caution Do not flame electrodes Doing so will cause them to melt and invalidate any warranty Cleaning the STX2 Electrode With use the electrode surface can become coated with foreign materials This build up or contamination will degrade the performance of the system resulting in slow or drifting vo...

Страница 15: ...leave the electrode in alcohol for more than 30 minutes each time Continuously soaking the electrode in alcohol will weaken the protective coating on the electrode and shorten its lifetime In a laminar flow hood 1 Immerse the electrodes in 70 ethanol for 15 minutes Allow them to air dry for 15 seconds 2 Rinse the electrode in a sterile electrolyte solution similar to the experimental cell culture ...

Страница 16: ...ower most of the electric circuit including the display When this set of batteries is low the LO BAT will appear on the digital meter Therefore this set of batteries does not need to be changed until the display indicates The second set of batteries contains only one 9 volt alkaline battery that is used to power the electric current injecting circuit There is no low battery indicator for this batt...

Страница 17: ...ultiwell Plate STX100C96 STX100 for Corning HTS 96 Well Plate CELL CULTURE CUPS WITH SYNTHETIC MEMBRANES CaliCell 12 12 mm Calibration Cell for Endohm 6 and Endohm 12 CaliCell 24 24 mm Calibration Cell for Endohm 24 OTHER 7364 Cidex Plus quart LAB TRAX 4 4 Channel Data Acquisition System Electrode Adapter WPI 3993 converts the four contacts in the phone plug into four independent 2 mm jack It allo...

Страница 18: ...lity of the System Unlike the STX2 the inserts have to be transferred from the culture plate to the Endohm chamber to make a measurement CaliCell is a cell culture insert with a synthetic membrane which mimics a confluent epithelial membrane s resistance in fluid Each CaliCell insert is has an established resistance measurement determined at the time of manufacture and against which the system res...

Страница 19: ...is no quantitative method available to do an in situ or wet test on the electrode However two qualitative methods may assist the user in determining that the electrode is working and will respond to an increase in resistance 1 Use WPI s CaliCell to test the electrode CaliCell is a cell culture insert with a synthetic membrane that mimics a confluent epithelial membrane s resistance in fluid Each C...

Страница 20: ...needs to be replaced 2 Meter reading is not stable when the power is turned on Check the Mode switch if it is in V mode the display will not be stable when the electrode is not in the solution This is normal If the meter is in R mode the meter display should read zero unless the Measure R button is pressed If it does not the meter is malfunctioning Call WPI Technical Support for assistance 3 Non z...

Страница 21: ...nge the batteries as necessary b ZeroΩ is not adjusted correctly See INSTRUMENT SELF TESTS Testing the Electrode for Resistance Measurements c System requires calibration as the meter ages the test reading is expected to drift slightly downward However this drift is normal within 1 accuracy at 1000 ohm If the error is more than 1 10Ω then the accuracy of your measurement will have a error that is ...

Страница 22: ...the Instrument Self Test to confirm that the meter is functioning appropriately If the problem persists the likely cause is the electrode Try cleaning the electrode see the section on Cleaning the Electrode If the problem is not corrected this indicates a failure of the electrode and the electrode needs to be replaced 18 World Precision Instruments ...

Страница 23: ...Current 2k Range 20 µA 12 5 Hz 20k Range 2 µA 12 5 Hz PowerOne 9 V alkaline battery six 1 5 V alkaline AA cells BNC Output of EVOMX 1 Ω mV when the Range Toggle Switch is at 2000 Ω 10Ω mV when the Range Toggle Switch is at 20 KΩ Dimensions 20 cm x10 cm x 5 cm Weight 3 lb 1 4 kg World Precision Instruments 19 ...

Страница 24: ...t the electrodes Sterilize the electrodes optional Perform measurements 20 World Precision Instruments For Voltage Measurements Connect the electrodes to the EVOM Equilibrate the electrodes with the power off Sterilize the electrodes optional Turn on EVOM After 15 min in the V mode adjust the Zero V screw with a small flat head screwdriver until the meter shows a reading of 0 0 mV Perform measurem...

Страница 25: ... 6 well inserts and STX electrodes Note that the resistance readings from 24 mm diameter tissue culture inserts used in 6 well plates obtained by using WPI s STX series of electrodes will be 1 8 to 2 2 times higher than that obtained using the Endohm 24 This is because the STX electrode cannot deliver a uniform current density over the relatively large membrane through the small gap between the me...

Страница 26: ...s of electrodes above and beneath the membrane the Endohm reduces background resistance with a blank cup inserted from 150 Ωto less than 5 Ω except Endohm 6 which is higher The shape of the current electrodes allows a more uniform current density to flow across the membrane With fixed electrode geometry the variation of readings on the same sample is 1 2 Ω as compared to 5 10 of the total reading ...

Страница 27: ...tissue R Total 800 Ω R blank 130Ω 670Ω Unit Area Resistance As the resistance is inversely proportional to the area of the tissue instead of reporting resistance typically the product of the resistance and the area is calculated and reported The unit area resistance is independent of the area of the membrane used and may be used to compare data obtained from inserts of different sizes NOTE Resista...

Страница 28: ...m2 580 Ω is the resistance of a unit area of 1 cm2 The larger the membrane the lower the resistance The dimension is Ωcm2 not Ω cm2 This may be confusing to a new user who might expect to divide to find the resistance of a unit area A further illustration may help to reinforce this concept Assuming a 1 cm2 membrane has a resistance of 500 Ω then a 5 cm2 membrane will have a resistance of 100 Ω not...

Страница 29: ... damage to data or property that may be caused directly or indirectly by use of this product Claims and Returns Inspect all shipments upon receipt 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 All claims for shortage or damage must be made within 10 d...

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Страница 31: ...EVOM ...

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