I own a DS1102E oscilloscope with 1x/10x switch on the probe, and I need to measure voltage output from the MEMEs driver similar to MAX14515 (I can not find the exact datasheet for MAX14574). The driver provides 0-140V biased at 70V at 5kHz wave.

  1. Is it safe (for the chip and the oscilloscope) to measure the voltage between GND and outputs (p.5-2 says 400V max input, just want to make sure I got it right)?

  2. Should I have 1x or 10x attenuation on my probe when measuring this voltage magnitude at the given switching frequency?

I would appreciate the explanation on under what conditions 1x/10x setting is best fitted (i.e. high frequency, low voltage, high voltage, input/output impedance/capacitance...).

  1. Yes, presuming the chip can drive the probe impedance (usually 1M ohm for 1X and 10M ohm for 10X)
  2. You probably want to use the 10X setting. The probe should present a higher impedance in the 10X setting and therefore load the circuit less. It also divides down the voltage that's passed along to the scope so that you're less likely to saturate the input stage.

Generally you want to use 10X. The only time 1X really makes sense is when you are trying to measure a really small signal level that gets buried in noise with the 10X attenuation. Most of the scope probes that I have are fixed 10X with either 10M or 2.2M impedance.

  • 1
    \$\begingroup\$ +1 Always use x10, unless you really have to use x1. \$\endgroup\$ – Neil_UK Nov 21 '16 at 19:54
  • \$\begingroup\$ And when you really have to use x1, it may also make sense to look in to using an external amplifier of some sort. I have an AM502 and ADA400A that I keep around just in case I need to look at something really small. \$\endgroup\$ – alex.forencich Nov 21 '16 at 20:01

Looks like data sheet 400v absolute max is correct - for the oscilloscope BNC input. Probes also have a max voltage rating - check that your probe can take large AC as well as DC voltages.
Since vertical range can be set to 10v/div, a screen can show a span of perhaps 80v if your probe is on X1 position. For displaying large voltages, X10 attenuator could show all.
For probing high-frequency circuits, or for examining digital logic rise time or fall time, the X10 attenuator should always be used, since it isolates much of the probe's cable capacitance from loading your circuit.
Be aware that probe compensation is required when using X10 attenuator. Your probe should have an adjustment for adapting your probe to your specific oscilloscope. Switching to a different X10 attenuator probe should be accompanied by setting or checking probe compensation. Your oscilloscope should have a built-in square-wave source for setting up compensation. Probe compensation video


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