WPI EVOM - Appendix C: Improving the Accuracy and Repeatability of the System

EVOM™ Manual
World Precision Instruments 45
APPENDIX C: IMPROVING THE ACCURACY AND
REPEATABILITY OF THE SYSTEM
Whenever possible, operate the EVOM™ Manual meter with the battery charger
disconnected. This ensures maximum electrical isolation for the most accurate
readings. When the charger remains connected to the meter during measurements,
electrical noise can be introduced into the system. For the highest accuracy in
measurement, WPI recommends disconnecting the unit from the AC power source.
Choose an electrode based on your application (size of the inserts: 6 mm, 12 mm, 24
mm and transwell type).
• EndOhm electrodes by design are considered more accurate in capturing
smaller changes. However, cell culture inserts need to be physically moved
out of the plate to the EndOhm chamber for measurement.
• STX HTS electrodes are ideal for high throughput screening (HTS) plates.
• With STX electrodes, you can measure inside the well plate. The STX4
electrode is our new and improved version of the STX2-PLUS electrode. It
has removable blades.
Fig. 73 demonstrates how the EVOM™ electrodes measures TEER. With a xed
centered electrode geometry of the EndOhm, the variation of readings on the same
sample is 1-2 Ω, as compared to 5% of the total reading using the STX2 electrodes.
An EndOhm, together with the EVOM™ Manual, oers the most accurate, convenient
and economical solution for trans membrane electrical resistance measurement. For
automation of TEER measurements, consider the REMS AutoSampler that integrates a
robotic system and computer interface to automatically measure tissue resistance in
24- and 96-well plates.
STX4
EndOhm
STX2
Fig. 73—This comparison shows how the electrode geometry can aect readings.