Digital oscilloscope maximum input voltage

Question

I recently bought a new GDS-1052-U oscilloscope. I read a few pages from the oscilloscope manual and I found that the maximum input voltage is 300Vpeak.

I have a question regarding the maximum input voltage: Is 300V peak the maximum voltage input for 10V/div or for 2mV/div using a 1x probe and AC coupling?

Will the oscilloscope be damaged if I set the vertical voltage to 2mV/div and connect the 1x probe to 200V peak? I know that the 200V peak voltage cannot be displayed on the screen if the vertical voltage is 2mV/div, but I want to know what can happen?

The last question: What is the maximum DC input voltage, using a 1x probe and DC coupling?

Answer 1

The maximum voltage is ±300V, period.

It doesn't matter what the settings on the scope are, or whether the voltage is AC or DC.

Any voltage less than that will not damage the scope, but what you see on the display may or may not be useful, depending on the settings.

You can use a 10× probe to measure higher voltages — up to whatever the probe is rated for — but if you ever switch the probe to 1× while doing so, you'll be violating the scope specification.

Answer 2

Dont confuse multiple specs. Separate them.

See below datasheet on p139

The DSO measurement capability spec is 300V AC+DC , THIS MEANS that you can measure 300V off the screen by using the vertical offset dial.

A different item is the human safety limit " 300V CAT II" but is capable of withstanding the standard 2.5kV impulse test

This assumes the x1 probe.

There are safety measurement zones called Category I,II,III,IV... **

This instrument is only rated for CAT II. Beyond this can be fatal to the user at the same voltage.

• CAT I is safe low voltage & current.
• CAT II is 300V max but limited to protected residential outlets. but IEC certification tests include exposure to 2.5kV impulse tests.
• CAT III is inside the breaker panel ( ie. connected to grid with greater risks)
  • which is restricted for use with this instrument, even though it is the same voltage.

** This is due to ARC Flash prevention limits due to energy , current limit and protection categories to prevent fatal measurements in CAT III e.g. spontaneous human combustion. ( sorry to be so graphic )

Answer 3

I once measured an 800V waveform with a standard 10 to one scope probe. I built an adapter to connect between the scope and the probe. The adapter was a resistor in parallel with the 1MΩ of the scope input and a parallel capacitor. This caused more voltage drop across the 9MΩ resistor at the tip of the probe. I had to work with the cap value to get a clean square wave using the scope calibrator. And I also had to place a brass shield around the adapter to make it operate properly. I may have been lucky with the shield as once I tried that, it worked perfectly as a 2 to 1 adapter. I suspect my resistor was a 1MΩ in parallel with the 1MΩ scope impedance. The cap, I don't know. HA!! I still have it after 25+ years. I'll post a picture. It is covered with heatshrink, so I measured the resistor at 952kΩ and the cap at 105pf.