An older 20 MHz dual channel Leader analog. Testing secondary ignition pattern on car, using inductive clamp for trigger (#1 spark plug wire), and capacitive p/u on inverted Chan 2 (on HT coil wire to distributor)
Is it normal for the trace signal to progressively & substantially dim at faster Time/Div settings? Occurs on both Normal and Auto trigger. I don't think adjusting the trigger level helped, but will retry that.
Thank you, Lance
LanceM wrote in news: snipped-for-privacy@arbitrary.net.digitex.net:
I would think it is normal.The phosphor is energized less by a faster sweep(lower duty cycle),thus less light emitted. Note that at very slow sweeps,the brightness goes UP,if there is no dimming circuitry to protect the phosphor.Some scopes had burned phosphor(lines) due to slow sweep speeds at too high an intensity.Newer scopes have beam-regulating circuitry to keep trace intensity fairly constant over a wide range of sweep speeds.
Jim's right - the electron beam doesn't stay on the phosphor long enough to excite it to high brightness. That's the advantage of a digital 'scope.
You might try a light hood - make one out of cardboard with a relief for your nose and duct tape it to the 'scope.
Don
NRA ARRL ATOS
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