Old oscilloscope not measuring frequency accurately.

[HerbertMunch]

Hi,
Ive just bought an old scope, Fluke pm3082(ebay).
Heres my problem:

The scope has a 2KHZ test oscilator. When i attach a probe to this and use the cursor function to measure the period, the unit can automatically calculate the frequency.
If i position the cursor correctly, it reads off 2.21Khz instead of 2khz.

Anyone know how to resolve this?

Many thanks

 

[Dean Huster]

There may be no problem at all. Even the kings of oscilloscopes, Tektronix, rarely had a calibrator output that was accurate as far as frequency. Amplitude, yes. Frequency, no. There were one or two models that actually had a tweak for setting the calibrator frequency to exactly 1KHz, but that was very unusual for them. Check your timebase against a known-good frequency source, such as the low voltage output of a mains transformer (60Hz in the U.S., 50Hz in the U.K.) or better yet, the output of a crystal oscillator.

Dean

 

[HerbertMunch]

Ok many thanks Dean.

 

[HerbertMunch]

Ive just tried what you suggested, and it measures 50hz exactly.

Your advise was Spot on mate.

thanks again.