QUESTION: Battery Powered Operation
Thanks Dave for the teardown--I now have a new 'scope. The HMO1212 is every bit as usable as was indicated in the #842 and will be my portable for work outside the lab. Battery power was speculated in the blog, so I had to check that out. Why? Some of the work I do is on boats and the AC comes from inverted DC (enough on that).
The three-wire cable from the 'scope internal PS to the board is 12V, ground and an AC signal for line-sync, so the battery in my design would substitute for the PS as needed using a barrel plug with a 'disconnect' on the PS 12V when it plugs in. No problem there.
The 'scope draws about 1.3A when working and a bit more on startup, so my battery choice would be a LiPO 3S with 5,000mAH capacity. I bought a Mean Well 12V DC-DC converter for the input thinking that it would keep the 12V steady. Testing the setup with a voltmeter and an electrical load showed that the LiPo battery voltage was far more stable than the 'regulated output' from the converter--probably a good explanation, but I don't have one--so I have had a re-think.
What about using the LiPo without the regulator? Fully charged it is ~12.4V and drops down to 12.3V under a load of 1.3A (like the 'scope). As the battery is drained, the voltage goes down: now 11.85V after 45 minutes. I would not run much below 11 volts for the work I envisage doing on battery.
Here's my question: How 'safe' is it to operate the HMO1212 on voltage ranging from 12.4V to 11.0V? (assume that there is no sagging on changes in the settings on the scope) Also, how safe is it to test this in advance by varying the voltage with a bench PS using the three-wire cable above? (Note: I have tried this without any indication of trouble, but that might just have been luck)
(By 'safe' I mean for the HMO1212, not for me--the mains cord is disconnected, etc.)
Thanks,
Donal
Update: my HMO1212 operates 'as normal' from 11.0V to 12.5V on the bench PS. Below 11V there is a change in the display of a 1 MHz trace as Dave used for the FFT demo.