Checking voltage on JC40 charger cradle

[pyite01]

My battery stopped charging, so I thought I would check the charger with a voltmeter. It looks like -0.7 V across the little +/- metal points (on the JC40). Should it read 5.2V across these? Or can you not measure it like this? I noticed a new charger is $50 on ebay, so I didn't want to buy one unless I was sure my charger was at fault.
thanks.

[amoon]

UPDATE

You can measure the voltage you have to press down the small round pressure switch on the cradle base to measure the voltage on the + & - pins. I just checked mine and it reads 5.05V via the USB-PC charge.

Sorry my mistake