Re: Tektronix 50 Ohm Terminator / Attenuators

Fabio Trevisan

Hi There,
Thank you all for your inputs.
With that info I know now what is useful to get.
Regards from Brasil

2017-05-24 14:36 GMT-03:00 David @DWH [TekScopes] <

On Wed, 24 May 2017 12:57:51 -0300, you wrote:

I have 3 questions about those attenuators:

1. Are they prone to malfunction, or degradation of any kind or... as long
as they're not burned-out I can consider them to be in working order?
I have yet to see one which was damaged unless overloaded in which
case a DC resistance reading will reveal the problem. I have never
seen one which had a good DC resistance and bad AC response but I test
both anyway.

2. About their impedance... Do they present 50 Ohm INPUT impedance, as
as 50 Ohm output impedance?
Feedthrough terminations have a short from input to output and 50 ohms
of resistance from either side to ground.

Attenuators present a 50 ohm resistance at their input and output
assuming a 50 ohm load on the other side so testing them this way
requires a termination or feedthrough termination.

3. About their attenuation factor, does it take in account for being
by 50Ohm at its output, or the attenuation factor is the voltage divider
factor per-se, and it will be further halved when connected to a 50 Ohm
The attenuation factor assumes both a properly terminated source and a
properly terminated load. If you drive them with a zero source
impedance like from a power supply or if you are measuring the input
at the attenuator, then they have 6dB (2x) less attenuation into a
proper load; I have done this for DC calibration where I need a much
lower reference voltage than I can easily produce.

At last, are any of those attenuators rare, or collectible or of
interest to anyone in the group?
Neither the 2.5x nor 5x standard attenuators are particularly rare and
both have modern equivalents. The 2.5x attenuators are a little less
common because they are mostly only used for oscilloscope calibration.

I have two of the 50 ohm 5W feedthrough terminations. At some point
Probemaster was selling the same part so I suspect someone else was
OEMing them for Tektronix.

The precision termination is pretty specialized but I forget where it
was used.

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