Replacing the battery in a HP 3478A Multimeter

Posted: April 11, 2013 in Test Equipment


I really like this bench multimeter.  It’s amazing to me that a piece of equipment that was made in 1986 has an accuracy that is indisguishable from that of a 6 month old Fluke 87V.  The word on the Internet is that the 3v Lithium batteries on these have begun to die.   Not many batteries can last for 27 years.   I’ve heard that they hold voltage until the very end and then they are done for.  The problem is, that the calibration data is held in volatile RAM.   When the battery dies, the data is lost and the unit is totaled.  A recalibratoin is more than you can buy them for.

A suggested replacement is the:

Digikey #P226-ND Panasonic Batt Lithium 2/3A CYL W/PCM PINS

So, the trick is to get the battery out without losing the calibration data.

You can build a battery backup to temporarily provide the 3…

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