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Namir · (This post was last modified: 06-13-2024 02:13 AM by Namir.)

Out of curiosity, I set my new multimeter to read resistance and poked the leads into the battery contacts of an HP-41CV. It read ZERO!! I repeated this test with different CVs and two CXs and got the same thing! Shouldn't my mutimeter be reading something regarding the resistance of the machines??? Am I doing something wrong? I did test the leads on a USB port of an external hard drive and got 10 M-ohms reading. So I know my multimeter works.

Namir

PS: In the next message I point out that the multimeter aso reads ZERO (instead of inifnity) when there is no connection.

Namir · (This post was last modified: 06-13-2024 02:12 AM by Namir.)

When I repeated the above tests wih an hP-67 and HP-45 I got the same readings of ZERO when their physical switches were OFF. When I turned the switches to ON, my multimeter registered a value!!! Bingo!!

My comclusion is that the HP-41C/CV/CX have "digital" switches that need batteries to be activated!!! In OFF mode the battery terminals look like they have a short!!!

Also, my multimeter reads zeros ohms when the leads are apart. So it treats zero and infinity as the same! The makers were too cheap to put an infinity symbol!

Namir