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Ohmmeter Battery Compensation

December 3rd Fact-of-the-Day

Most ohmmeters use one of two different methods to allow users to make compensating adjustments as batteries discharge. One method consists of connecting a user-adjustable resistor in series with the battery. That method is based on the assumption that batteries generate constant voltage during their life, but that their internal resistance increases as they discharge. The other method consists of connecting a user-adjustable resistor in parallel with the meter. That method is based on the assumption that battery voltage drops as a battery discharges, but internal resistance remains constant. Neither assumption is true, but ohmmeters based on either assumption are accurate enough for most ordinary ohmmeter applications. ©2004 Martek International All rights reserved.


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