surface mount resistors

I am trying to repair a circuit board where several of the surface mount resistors have come lose.
I am trying measure the resistance, but the measured values don't quite match what is stamped on top.

The resistors that have "180" on top, almost exactly have that as a measured resistance ohms.

The resistors that have a value of "510" stamped on top, have a measured value of "50".
Is there a implied decimal point ??
sidwelleAsked:
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JohnBusiness Consultant (Owner)Commented:
Is there another resistor of the same stated value to measure?  Unless there is a K or M or some other marking, you would expect the resistor in question to be 510 ohms, just like the 180 ohm resistor. There is not a standard for printed values but markings usually make it clear.

You need either a comparable resistor or manufacturer spec sheet to be sure.
funwithdotnetCommented:
Ignoring measurement technique- a number may match or be totally unrelated to resistance. You can't count on it. Even a match can have quite a bit of tolerance.  *If the package is not charred or damaged and is connected properly, there is a 99%+ chance that it will work properly, regardless of the measurement. *A rule of thumb from way back in my circuit component troubleshooting & repair days.
JohnBusiness Consultant (Owner)Commented:
Mostly today, numbers on a component have meaning. This is true for the stuff in my shop downstairs..
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funwithdotnetCommented:
I forgot ... 510 = 51 ohms.

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JohnBusiness Consultant (Owner)Commented:
So then why is the "180" ohm resistor measuring 180 ohms. A given manufacturer would use the same numbering technique (which may not be standard).
sidwelleAuthor Commented:
JohnBusiness Consultant (Owner)Commented:
Thanks. It is always the spec sheet that will tell you.
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