Products > Test Equipment
PicoScope 2000
alank2:
Here is another reason I love the picoscope: Their support of custom probes and the software lowpass filtering. I have a PDI 20A/60A small current clamp and it is so noisy. I've been meaning to ask if the hantek one I see has about the same level of noise. See the noise.png, it looks like 100mA wide! custom_probe.png shows me selecting the custom probe I setup for the PDI current clamp. Picoscope has a great feature (custom_ranges.png) where you can automatically map up the scope's vertical ranges. You can even specify the probe's limits so you will get an over range warning for the probe itself which is why it shows 60% of the scope's range being mapped to the maximum current the probe can handle. I can settle the noise considerably with the low pass filter (lowpass.png) which finally gives me something I can make some sense of (low_pass_filtered.png). Even holding down the "zero" button on the scope though does not get me as close to zero as I would like. Then, even though I am in my lowest scope range and can't go lower, I can use scaling to zoom vertically by 10x (scaling.png). Now it looks like off is averageing -2mA or so, and when I power up the device I am monitoring with the clamp (LCD backlight), it jumps from -2mA to probably around +22mA average, giving me a current use of 24mA for the backlight. I didn't think with all the noise this clamp has that I could use it to measure low currents as well as I can.
MrW0lf:
Wanted to comment on little feature finding good use lately. One can share entire workspace with all traces, reference waveforms, mathchannels and whatnot. Transport file to another PC and make offline postprocessing & thinking without actual scope present but with exact look & feel as doing real testing.
Example: I commute a lot between 2 cities. Along the way lives inventor-friend who has shed. In the shed weird and wonderful things are being built. For example this:
Currently it's using hardcore mechanical commutation with fireworks and EMI that can kill small animals on spot. Decided to built solid state driver for it. So when driving by took measurements in 15 min. Analysis later at home in peace & quiet w/o lightning strike risk...
Attached file with entire workspace. Main challenge was to decide how combine coils for driver, since signals are all out-of-phase and non sinusoidal. Currently seems combining 2 coils for each "cylinder" in series will yield more-less sinusoidal, so 2 independent drivers needed.
MrW0lf:
Inspired by alank2 post about custom probes managed to improve some old tricks. Developed them long time ago when had only 2ch analog 2205 and often shortage of channels. General is idea is to "tunnel" (discrete) information thru scope analog channel and display after math-based reconstruction. This can be useful when monitoring some process governed by MCU. Either to monitor some single signal that cannot be directly monitored or even use discrete stepped analog for "tunneling" some state or error codes = true digital comms.
Very simple setup to start experimenting with is Arduino Uno + MCP4725 12bit DAC breakout. This will push nowhere near scope speed capability but good for proof-of-concept.
DAC setup info can be found here. Then just connect DAC output to regular probe on 1X setting.
Next need some test signal. To maximize scope ADC range w/o risk of overrange due to noise I did choose +-2V with -2.5V analog offset. On Arduino (sketch attached) mapped DAC to 0...16 values using
--- Code: ---dac.setVoltage(map(dLevel, 0, 15, 485, 3560), false);
--- End code ---
Result on scope:
Now we have seed for simple 4bit "comms signal". Possibly could push for higher bit count, but I'm currently in very noisy environment (CCCP-style electrical system w/o grounding) so will go for 100% reliability. How to convert this noisy analog signal to true digital will be shown in future posts.
MrW0lf:
Next step is to to configure custom probe to start closing in on true digital:
Custom Probes => [New Probe...]
Check "Use the custom unit defined below."
Full name: digits
Short name: D
For scaling method use linear equation: y=4x+8
Choose manual management of probe ranges.
Click [New Range...]
Fix hardware input range to +-2V
Set scaled range limits from 0D to 16D.
Do not enable filtering (or resolution enhancement)!
Name for probe MCP4725
Now signal is having nice 1D step instead of some non-human-readable voltage variation:
MrW0lf:
Now time for uncharted territory. How to get rid of noise and remains of analog part? floor(x) function would certainly help. But PicoScope 6 software AFAIK does not have floor function. But it does have trigonometric functions! So here goes:
Define math channel floor(D)
Set long name as digit, short name as D. Override automatic range, set min=0, max=16.
Now we have true discrete/digital comms estabilished:
This can be used to channel error codes, state codes or any other purely digital data to DSO having only analog channels, sacrificing only single analog channel. Or maybe even create virtual MSO (explained later).
Note that doing RT trigonometry on full record may slow down refresh rate so makes sense to lower sampling rate to avoid excessive processing and match actual need.
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