Old 'scope adventures

[John Marsh]

Hi everyone,
I have an ancient Heathkit 10-12U oscilloscope,full of valves (tubes)
and great for airing laundry. It seems to be only AC coupled; i.e.
connecting a steady DC source produces a brief jump of the trace. If I
connect a source of pulsed DC which peaks at 9V, how do I interpret &
calibrate the trace? Pulse generator is a 555 timer as astable.
Viva valves,
John.

 

[Jamie]

look on the input line, or some where around it.
you should have a switch that saids DC/AC input.

 

[John Marsh]

look on the input line, or some where around it.
you should have a switch that saids DC/AC input.

Thanks for your reply Jamie;there is no such switch on this
oscilloscope. It is very old.

 

[BFoelsch]

Oscilloscopes of that general design were not calibrated at all. About all
you can do is apply a known signal and use that as the calibration standard.

Yes, most inexpensive scopes were also AC coupled. The "zero" will be a line
through the waveform with equal area above it and below it. Even this will
be in error if the waveform you are viewing contains a DC component or
contains very low frequencies

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hi everyone,
I have an ancient Heathkit 10-12U oscilloscope,full of valves (tubes)
and great for airing laundry. It seems to be only AC coupled; i.e.
connecting a steady DC source produces a brief jump of the trace. If I
connect a source of pulsed DC which peaks at 9V, how do I interpret &
calibrate the trace? Pulse generator is a 555 timer as astable.
Viva valves,
John.

You adjust the calibrate (if it has one) until the trace has 9 vertical
divisions on the graticule (if it has one).