Farnell DT12-5 manual - What does this mean?

[GordonB]

I recently picked up a reasonable condition Farnell DT12-5 oscilloscope for next to nothing and found that apart from the focus tending to drift it works fine. However, it's clear that it isn't calibrated. I've got a pdf copy of the manual and in the section on setting the calibration waveform it states; "Adjust P2 on trigger boards to obtain 1V as accurately as possible. Check that the frequency is 1kHz + or - 200Hz. If necessary S.O.T. R31." There is no explanation of what "S.O.T." means, can anyone interpret for me?

Many thanks
Gordon

[wasedadoc]

Select On  Test.

Means you try some fixed resistors until you find one that results in the measurement being in spec.

If both horizontal and vertical axes are out of calibration that could be caused by voltages on the CRT being too far off nominal.

[GordonB]

Select On  Test.

Means you try some fixed resistors until you find one that results in the measurement being in spec.

If both horizontal and vertical axes are out of calibration that could be caused by voltages on the CRT being too far off nominal.

Many thanks for the quick reply, that now makes perfect sense. It's only the Y axis that seems to be out of calibration and I'm not too keen on messing around with the high voltages on the CRT. I'm borrowing another oscilloscope later today so I can check the calibration signal.

[tggzzz]

Select On  Test.

Means you try some fixed resistors until you find one that results in the measurement being in spec.

If both horizontal and vertical axes are out of calibration that could be caused by voltages on the CRT being too far off nominal.

Many thanks for the quick reply, that now makes perfect sense. It's only the Y axis that seems to be out of calibration and I'm not too keen on messing around with the high voltages on the CRT. I'm borrowing another oscilloscope later today so I can check the calibration signal.

I wouldn't bother with changing R31 to get 1kHz. The cal out signal's principal purpose is to enable twiddling of the compensation capacitor in 10Mohm "high" impedance *10 probes. The frequency doesn't need to be exact for that; even 10kHz or 100Hz would be OK.

Be aware that analogue scopes are only likely to have a 2% accuracy rating. That doesn't matter, since their purpose is to see the waveform shape; the transient response is the important metric.

[liaifat85]

Here are also some info about this oscilloscope model. You can check these out.

[GordonB]

Here are also some info about this oscilloscope model. You can check these out.

Can't see any links.