Re: oscilloscope
- From: John Popelish <jpopelish@xxxxxxxx>
- Date: Mon, 18 Jun 2007 11:44:27 -0400
spamfree@xxxxxxxxxxx wrote:
I'm a newbie wanting to muck about with picaxe projects partly to
learn and partly to make some long-wished-for gadgets, eg datalogging
battery charging and meteorological/power generation info, and a
keyless front door lock.
I'm confused about the pros and cons of these two CRO alterrnatives.
The first seems to be a cheap analogue machine. Costs new about $US 350
The second, a USB computer-based "black box" that doesn't seem to want
to tell me what the bandwidth is. Maybe it's in there somewhere, but I
don't know enough to tell. This is around $US 250
I'd appreciate any advice regarding the usefulness of these in general
electronics, picaxe, and education for me.
Cheers, jack
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20Mhz Dual Channel Cathode Ray Oscilloscope
SPECIFICATIONS
Vertical Deflection Sens.: 5mV - 5V/div (10 steps 1-2-5 seq.) Bandwidth: DC to 20MHz Rise time: 17.5ns Input impedance: 1MO with 25pF shunt Max input voltage: 300V (DC and AC p-p) Input coupling: AC, GND, DC Modes: CH1, CH2, ADD, DUAL CH1 output: Min 20mV DC Horizontal Deflection Sensitivity: 0.5sec/div, (20 steps 1-2-5 seq.) Accuracy: ±3% Trigger Modes: Auto, Norm, TV-V, TV-H Source: CH1, CH2, LINE, EXT Slope: Positive or negative Ext. input impedance: 1M with 25pF shunt Probe Adjustment Frequency: 1kHz (20%) Level: 2V (±2%) p-p Duty ratio: <48:52
X-Y X Axis bandwidth: DC to 500kHz X-Y Phase diff.: 3° or less (DC to 50kHz)
Z Axis Input impedance: 47kO Input signal: +5V (positive INPUT) Max. i/p voltage: 30V Bandwidth: DC-2MHz Power Power supply: 220VAC General Dimensions: 310(W) x 150(D) x 455(H) mm Weight: ˜8kg
CRT 6° tube: Rectangular face (8 x 10div)
Features
• 2 channels • Variable sweep • 10x magnification • 4 trigger modes, auto, norm, TV-V & TV-H • Wide bandwidth and high sensitivity • Easy to read 6” display • Bail-arm stand for ease of viewing • Carry handle • Very low power consumption • High sensitivity X-Y mode • Z axis (intensity modulation) • TV video sync • Filter • High frequency rejection filter in the triggering circuit • Supplied with 2 high quality test probes
This sounds like a very ordinary, low end, 2 channel analog scope. It would have lots of uses for audio and other analog signals, and also digital, except for the timing details of digital edges. Even a small, slow microprocessor would might react to things you would miss or see distorted with only 20 MHz bandwidth. But still potentially very useful.
The only feature missing that you might find a need for, is delayed sweep. when you are looking at digital sequences, you sometimes need to examine a detail that is significantly delayed from a trigger event. If you use a horizontal sweep time long enough to get both the trigger event and the one you want to see on the screen at the same time, the details are too crowded together to make out anything useful. Delayed sweep is 2 sweep generators. the first starts at the trigger event, and acts as a programmable delay, that triggers the second, which sweeps the trace. In effect, you get a programmable delay between the trigger event and the expanded trace of some period of time after it. But you can, also alternately, see the whole time period, but with the delay portion dimmed, and the delayed part brightened, so you can set the delay.
##########################
2 Channel USB Oscilloscope
At last! A genuinely affordable computer connect oscilloscope. USB
connect oscilloscopes out of Europe and North America have so far been
out of the price range for hobbyists, schools, and even many
professional people. Fortunately, we have been able to work with a
EUROPEAN manufacturer to produce this compact unit which is packed
with features and the European quality we've come to know.
Using the Plug 'n Play USB technology and providing full optical
isolation from the computer, this oscilloscope is easy to setup and
use, as well as providing protection for the computer. The software
(again developed in Europe) is a fully featured chart recorder,
function generator, logic generator, logic analyser, and spectrum
analyser all in one easy to use package.
We think you'll be suitably impressed by this product's price and
feature list.
Specifications
Oscilloscope, spectrum analyzer
Sample rate: 100 Hz - 200 kHz
Input voltage -20 - +20 V
ADC capacity: 10 bits
Window functions: Hamming, Hanning, Blackman, Blackman-Harris
Recorder:
Sample rate: 0.01 Hz - 200 KHz
Maximum record time: 24 hours
Input voltage -20 - +20 V
ADC capacity: 10 bit
I would say that these specs indicate an absolute bandwidth of less than 100 kHz, which is poor for any use except low frequency analog and audio stuff. Microprocessors can have a lot happen in 5 microseconds (the time between samples).
Logic analyzer:
Number of channels 16 (8 if logical generator is on)
Sample rate 1 KHz - 8 MHz
Input voltage: 0 - 5V
This seems to be referring to 1 bit resolution (recording if a signal is either above or below a threshold voltage, somewhere between 0 and 5 volts. A logic state recorder, not really an oscilloscope. But at least it is fast enough to follow more of the range of microprocessor signals. This sort of thing is normally called a logic analyzer, used to capture the parallel processes of buses or other multi bit processes.
Logical generator:
Number of channels: 8
Sample rate: 1 KHz - 1 MHz
Memory depth: 1544 bit/channel
Output voltage: "0" - 0 V, "1" - 3.3 V
Maximum input/output current: 10 mA
Very handy as a signal source simulating the missing parts of a system, when you are testing a part of a logic system
Minimum system requirements: Windows 2000 or XP
Pentium 600MHz, 256MB RAM.
.
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