Oscilloscope and probes

[ubxf]

Hello,
So far i've done most of my limited building and repair work with a multimeter but now i'd like to use a scope. I have an old HP1740A 100MHz scope and found a Tektronix P5100 2500 V 250 MHz probe would they work ok together ?
Thanks
F

 

[radardoug]

Yes probably. The HP has a 1V squarewave calibrator output. Hook the probe up to this, and if it has an adjustment, set it for best squarewave.

 

[ubxf]

Thank you, i was just curious to see if there was some kind of attenuation built in the probe to handle the high voltage that would make it incompatible for low voltage work.

 

[Khron]

Google is your friend. First result in the search for "Tektronix P5100" is the product page on the Tektronix website, where you can find the link to the manual for the probe.

https://download.tek.com/manual/070815105web.pdf
Once you scroll past all the ass-coverage (safety warnings etc) and reach page 16, the first (useful) sentence there is "The P5100 is a 100X, 2500 V (DC + peak AC), 1000 V CAT III oscilloscope
probe that provides 250 MHz performance."

So yes, as is relatively usual for such high-voltage probes, this is a 1:100-attenuating one (while for most oscilloscopes you'd be using a 1:10). That's not saying you can't use it at all, only that you'll need to keep the "signal displayed / vertical setting is 10 times smaller than reality" in mind. There may well also be a slightly higher noise floor.

 

[Winston OBoogie]

It's a 100X probe so has 40dB of attenuation. Whether that works for you depends on what you're measuring. 10X is my most used probe unless I'm looking at higher voltage H.T. lines on tube stuff.

Edit: Khron beat me to it

 

[Brian Roth]

I found the probe manual online and it is a 100X probe which means it attenuates the signal by a factor of 100. Not really good for lower level signals where you would use a 1X or 10X probe.

Bri

 

[Brian Roth]

LOL......we all were typing at once and I was the slow poke cuz I took a a few mins off to grab a beer, etc etc.

For eons, I've had probes with an onboard switch that goes between 1X and 10X.

Bri

 

[ubxf]

great, thank you guys. So i'll use it on tube gear and find another one for lower voltages.

 

[Newmarket]

For eons, I've had probes with an onboard switch that goes between 1X and 10X.

Bri

The x1/x10 switch is always the things that fails.
I now favour fixed attenuation probes for that reason (also can't accidentally get the wrong setting).
Some scope / probe combinations have pins to automatically detect the probe type/setting - Tektronix.
Bear in mind that the higher the attenuation the less load on the circuit being probed.
x10 works well for for most things not HV.

 

[Brian Roth]

Yes that switch can fail....yet was a standard Tek item since forever. I guess what our shops should stock is at least one pair of each 1X, 10X and sometimes 100X probes. A bit of a rat's nest <g> along with my BNC to:

male XLR, female XLR, XLR pin 2-3 flippers, phone 1/4" and RCA all built with RG-58 cable or Beldfoil 9451.

Indeed, a decent 10X probe has a lower capacitance/higher load resistance than a 1X. But, when sniffing around solid state audio circuits or PSU rails.... a 1X allows you to snoop better at low signal levels.

As always....use the correct tool for the task.

Bri

 

[Newmarket]

Indeed, a decent 10X probe has a lower capacitance/higher load resistance than a 1X. But, when sniffing around solid state audio circuits or PSU rails.... a 1X allows you to snoop better at low signal levels.

As always....use the correct tool for the task.

Bri

Yeah. My current instrumentation challenge in the day job is measuring small signals on relatively huge common mode voltages requiring use of x100 5kV probes.