I have been looking at getting a Rigol Oscilloscope for my test lab.  It would help with showing PWM projects on the Raspberry Pi and Arduino devices.  I tend to not get the most expensive components for my test lab.   I purchase components that will last 3-5 years and allow my projects to grow into them. 

1 Hz = 1 /seconds or 1 / 1 ms = 1000 Hz 
1/ 0.001 seconds = 1000 Hz =   1 = (0.001 seconds )(1000/seconds)

Think of is as 1000 Hz give you a period of 1 ms. 
100 Hz is a period of 10 ms  1/0.010 seconds =  100 Hz.

Generally, scopes will feature around 8-10 vertical (voltage) divisions, and 10-14 horizontal (seconds) divisions. Older scopes (especially those of the analog variety) usually feature a simple, monochrome display, though the intensity of the wave may vary.

This is the Rigol DS1104Z Plus oscilloscope.  It is in the $400-$500 range ($499).  It is considered a good starter for a home test lab.

  • 4 Channels, 100 MHz Bandwidth and 16 digital channels
  • Digital Logic Connector for optional MSO upgrade: RPL1116
  • UltraVision: Deeper memory(Standard 12 Mpts, Upgradeable to 24 Mpts)
  • UltraVision: Up to 30,000 wfms/s Waveform capture rate
  • UltraVision: Multi-Level intensity grading display
  • UltraVision: Realtime waveform record, Replay, function (Opt.)
  • A variety of Math Functions
  • FFT function
  • A variety of Trigger Functions
  • Optional Serial Bus Triggering and Decoding functions(RS232, I2C, SPI)
  • Standard Mask test function
  • Automatic Measurements with Statistics

Rigol MEM-DS1000Z Option Extends deep memory: Catalog: MEM-DS1000Z | Model: Rigol MEM-DS1000Z: $210 for 24 Mpts upgrade.

You can buy the DS1104Z-S Plus for $699 and it includes this extra memory.    To me, start out with the $499 unit and upgrade later to the extra memory to save upfront money.