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voltage limit of CA plugin

Jamie Ostrowski
 

Does anyone know what the upper voltage limit is on the CA plugins? I couldn't find the spec in the manual, and I'm interested in measuring ripple in a 550 VDC power supply so I want to be sure I'm not overloading anything.


Thanks,

- Jamie

Nenad Filipovic
 

No idea as well, but most likely it will be your probe that will determine
the max voltage to be worked on. That is if you're using the "usual" x10 or
higher attenuation probes like you should.

CA plugin uses a 600V capacitor for the AC input mode (which is what you'd
be using to measure ripple). Given the age of any CA today, I'd derate that
somewhat.

Tek P6007 or P6009 probes (x100, 1.5kV) would be suitable for your
application and most work on tube circuits. For low freq work like mains
ripple you might even improvise one using multiple resistors in series.

Best Regards,
Nenad

On Sat, Feb 1, 2020 at 6:54 AM Jamie Ostrowski <jamie.ostrowski@...>
wrote:



Does anyone know what the upper voltage limit is on the CA plugins? I
couldn't find the spec in the manual, and I'm interested in measuring
ripple in a 550 VDC power supply so I want to be sure I'm not overloading
anything.


Thanks,

- Jamie

Nenad Filipovic
 

Damn, I typed my answer before I was fully awake. HV probes are certainly
handy, but their attenuation might be a problem if you want to measure
noise in the millivolts range on top of a few hundred volts rail (case
common with tube voltage regulators). For that you might put the CA into DC
input mode and use an external high voltage capacitor (e.g. 100nF 1kV) to
filter out the DC component. But you'd also need a surge suppressor circuit
to handle charging of that capacitor once you touch the rail to be
measured. A 1K-ish wire-wound resistor in series with the external
capacitor together with two zeners (in series, cathode-cathode or
anode-anode connected) in parallel with the CA input might do the trick.
You could size the zeners according to the Volts/div range you'd be using
on the CA.

Best Regards,
Nenad

Jamie Ostrowski
 

Thanks Nenad. This gives me some things to think about. I also do have a
1A1 plugin so I may go with that. It is rated for 600V but to your point
due to the age I'm really pushing things to the max. I was just curious if
anyone knew about the voltage range of the CA since it is so common.

On Sat, Feb 1, 2020 at 4:56 AM Nenad Filipovic <ilmuerte@...> wrote:

Damn, I typed my answer before I was fully awake. HV probes are certainly
handy, but their attenuation might be a problem if you want to measure
noise in the millivolts range on top of a few hundred volts rail (case
common with tube voltage regulators). For that you might put the CA into DC
input mode and use an external high voltage capacitor (e.g. 100nF 1kV) to
filter out the DC component. But you'd also need a surge suppressor circuit
to handle charging of that capacitor once you touch the rail to be
measured. A 1K-ish wire-wound resistor in series with the external
capacitor together with two zeners (in series, cathode-cathode or
anode-anode connected) in parallel with the CA input might do the trick.
You could size the zeners according to the Volts/div range you'd be using
on the CA.

Best Regards,
Nenad



Albert Otten
 

The advantage of 100X probes P6007 and P6009 is that the divider is (mostly) inside the probe. Then the input capacitor sees not a high voltage.
Albert

John Williams
 

Jamie the input capacitor is specd at 600 vdc. That means that the input dc plus peak ac should not exceed 600.

Jamie Ostrowski
 

Thanks John. Is there a chance that even though that capacitor was spec'd
at 600 volts there may be a possibility that other components in the
circuit aren't - that they tossed in the 600 VDC rated capacitor because
they already had a large supply at that voltage rating at the factory that
they used in other designs when in fact the rest of the circuitry could not
actually handle the full spec of the cap? That's why I was hoping the
manual would say but it doesn't. I'm probably being overly cautious but I'm
a novice who has never played with these voltage levels before on this
equipment and I'm probably overthinking it.

You've been working with these scopes so long though if you think it's fine
then I'll give it a shot.

On Sat, Feb 1, 2020 at 3:49 PM John Williams <books4you@...> wrote:

Jamie the input capacitor is specd at 600 vdc. That means that the input
dc plus peak ac should not exceed 600.



Chuck Harris
 

If the little AC/DC/GND switch can handle the voltage.

Tektronix was silent on the issue, which usually means
you have to hope you are lucky.

-Chuck Harris

John Williams wrote:

Jamie the input capacitor is specd at 600 vdc. That means that the input dc plus peak ac should not exceed 600.