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| Looking for portable oscilloscope |
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| tggzzz:
--- Quote from: abgx1 on December 09, 2023, 01:36:15 pm ---I am about to buy my first oscilloscope. It will be used for measuring on frequency inverters (mains 400V voltages up to 16kHz), mains voltages in general, and industry sensors. Additionally, I may use it for car electronics. Measurements will usually be done on-site, in not-so-easily accessible places (like industry water wells in the middle of nowhere). After some research, I've narrowed it down to 2 options: 1. Rigol DHO804 https://www.conrad.com/en/p/rigol-dho804-digital-70-mhz-1-25-gs-s-25-mp-12-bit-1-pc-s-2986311.html - not very portable, but can be powered from a USB-C power bank. 2. Voltcraft DSO-2072H https://www.conrad.com/en/p/voltcraft-dso-2072h-handheld-oscilloscope-70-mhz-2-channel-250-msa-s-8-kp-8-bit-handheld-1-pc-s-2380256.html - handheld, with its own batteries. I'm also considering these probes https://www.conrad.com/en/p/testec-tt-hv-250-probe-300-mhz-100-1-2500-v-107255.html for both of them. Currently, I use a multimeter for these kinds of jobs, but I feel like I could find problems faster if I could see the actual waveforms. --- End quote --- You would benefit from reading and understanding the Tektronix references at https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/ especially the safety references. TL;DR is never float a scope. There are many subtle ways it could damage the UUT, and/or the scope, and/or you. A few scopes are explicitly designed to be used (relatively) safely in cases such as you describe, typically with isolated inputs. Make sure any probe's AC voltage-vs-frequency rating is not exceeded. If the probe doesn't have that specified, don't use it. |
| Fungus:
To be honest: For looking at basic 16kHz signals in outdoor conditions I'd be tempted to go for a single channel handheld. You don't need deep memory, serial decoders, video triggers, etc. for that. Something like that Voltcraft/Owon shown in the first video would do it. Look for one that can be charged with a USB powerbank. Maybe even this combined with a decent probe and a voltstick to check which is the live wire and which is neutral/GND: |
| adam4521:
Middle of nowhere, wells, water, 400V, inverter, it’s like a cacophony of jangling alarm bells. In most contexts this would be super-regulated industrial work. They’d start with whether you need to do the test in situ at all, then would follow detailed risk assessment, method statement, two people at least etc. Eventually, a comparatively low price/performance, but very regulated, isolated, tested device from premium supplier like Fluke might be suitable for the test activity, within a procedure that is entirely written out in advance. Dave has done videos on why those types of device exist and are expensive compared to the hobbyist devices. |
| alm:
I'd definitely look for a CAT III rated device designed for floating measurements with properly isolated or insulated (for single channel) connections, and not like the Voltcraft in the first post: "please don't touch the connectors while the scope is connected to a voltage source". |
| abgx1:
It's getting way more complicated and expensive than I thought. I think that intentional floating measurement is out of the game for now. If I understand correctly, the only problem I need to solve now is when I accidentally connect the ground to the mains voltage (which can easily happen). Now I see that I need to gain a lot more knowledge about scopes. I've read some articles and watched some videos, etc. [Here's a link]. But, what if I buy a scope operated from main voltage? In that case, the ground point will always be connected to the ground in the outlet. So, the worst-case scenario is a short circuit between the scope ground and mains voltage, which is not ideal but much safer than the risk of being electrocuted. Or should I abandon the idea of buying a scope completely until I'm ready to pay 3-4k€ for the Fluke? |
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