J
John Smith
- Jan 1, 1970
- 0
Hi -
I bought a Tek 468 which I returned today. I thought it had a problem, but
the seller disagreed. I would like to know if I am wrong.
The 468 is an analog/digital scope. In the digital mode, I noticed that the
trace had rectangular pulses on it of about .1 cm amplitude and apparently
random in frequency and width. This was with the inputs grounded using the
switch on the front panel. The amplitude of these pulses did not change when
I changed the attenuator setting except at the three most sensitive settings
of the attenuator (2 mV, 1 mV and .5 mV). Those three most sensitive
settings were active for digital storage operation only and were
non-functional in the analog mode.
When I complained about it, the seller said that it was caused by
quantization, it met Tek's specifications, and that .1 cm was entirely
reasonable. I disagreed because all waveforms appeared noisy so one would
never be able to tell whether the observed waveform was at fault or the
scope was at fault. In addition, .1 cm is 1 part in 80 for the vertical
displacement (8 cm vertical grid). It didn't seem right that maximum
resolution would be 1 in 80 or even 1 in 100. Logically, I felt that the
resolution would be 1 in 256 so that quantization noise would be much less
than actually observed.
Maybe I understand nothing about scopes and digital stuff. But, I could not
believe that Tek would sell such a product. Am I wrong?
Thanks for any comments.
John
I bought a Tek 468 which I returned today. I thought it had a problem, but
the seller disagreed. I would like to know if I am wrong.
The 468 is an analog/digital scope. In the digital mode, I noticed that the
trace had rectangular pulses on it of about .1 cm amplitude and apparently
random in frequency and width. This was with the inputs grounded using the
switch on the front panel. The amplitude of these pulses did not change when
I changed the attenuator setting except at the three most sensitive settings
of the attenuator (2 mV, 1 mV and .5 mV). Those three most sensitive
settings were active for digital storage operation only and were
non-functional in the analog mode.
When I complained about it, the seller said that it was caused by
quantization, it met Tek's specifications, and that .1 cm was entirely
reasonable. I disagreed because all waveforms appeared noisy so one would
never be able to tell whether the observed waveform was at fault or the
scope was at fault. In addition, .1 cm is 1 part in 80 for the vertical
displacement (8 cm vertical grid). It didn't seem right that maximum
resolution would be 1 in 80 or even 1 in 100. Logically, I felt that the
resolution would be 1 in 256 so that quantization noise would be much less
than actually observed.
Maybe I understand nothing about scopes and digital stuff. But, I could not
believe that Tek would sell such a product. Am I wrong?
Thanks for any comments.
John