Oscium iPad oscilloscope review
Brian Dipert sent me a pre-production Oscium oscilloscope to review. The scope is a single channel 5MHz unit that connects to your iPhone or iPad. It also has 4 digital inputs, which all my pals liked. Brian reviewed it already (twice), but we both thought we should get a working engineer to check it out. I gave the ’scope to my buddy Tim Regan, who is an amplifier application manager at Linear Technology. He’s the guy that keeps reminding me about their new TimerBlox parts, so I figured I would put him to work doing a scope review.
We tried it at the Pizza place last Friday on his iPhone, but Tim’s wife has an iPad, so he took it home to check it out. Here is what Tim said:
- Hooked it up to the iPad tonight. Looks nice and it’s much easier to use on the iPad than the iPhone. The phone display is cramped. If you try to reposition a trace at the bottom, you touch, and up pops a menu of selections which you don’t want. Much better arrangement on the iPad display with the menus out of the way.
- Still seems buggy. I haven’t seen a manual so I am just “button mashing” to try to get it to do what I want. I could be missing some settings that a manual should explain. Instead I simply noticed a few things that bother me. If it were my product and it was part of my job to evaluate it and feed back to the developers I would take better notes. Since it is not, I just get annoyed by a few things that don’t seem to work and I don’t want to spend too much time on it.
- Here’s a few notes:
- 1. Pinching and spreading on the screen isn’t super responsive. To change the volts or time scale can take several tries. If you accidentally do a diagonal it changes both scales and that’s annoying. I’d prefer a push button setting on the channel and a time base menu. It is also easy to lose the trigger reference point while changing the sec/div.
- 2. It’s response is sluggish. It looks like it samples about once every second. If your signal amplitude changes it takes a while for the scope to catch up. The constant pulsing of the traces is distracting.
- 3. It only has a 5MHz bandwidth so a 1MHz square wave looks a bit rounded which is fine. But when I put in a low frequency of 10Hz and set it to 100ms/div it stopped triggering. This even with the normal triggering setting. I have the same problem with some very expensive Agilent scopes also.
- 4. You can’t have the horizontal and vertical cursors on at the same time as far as I could tell. You often want to know the precise voltage at a particular point in time.
- 5. The analog trace looks really noisy with the attenuation of the probe in 10x mode. On the order of 200mV p-p of sinusoidal-ish noise on top of my 4Vp-p signal. 1x setting looked better. When I connected the digital pod ground input to the analog probe ground it seemed to clean it up. I noticed this just when I was about done with it.
- 6. The digital inputs aren’t buffered and will clamp the signal on the analog input. I wanted to see where the digital threshold was ( its about 1.5V) by connecting a digital input to my analog input. At about -0.7V and +3V the analog signal is clamped by the digital input channel. So don’t drive the digital inputs with analog signals! But that’s the kind of stuff we analog guys do isn’t it?
- I think this scope is a good idea. It is nice to be able to observe signals for at home troubleshooting and using your phone or iPad is convenient. Too bad they limit the analog input to 40V max so you can’t check the ac power line. That could be a handy capability. I think it could benefit from some meticulous field testing to refine it’s features. I gave it about an hour and found several issues. I am sure there are more.
He also sent another note to me-
- The analog trace display blinks at about a 3 second rate. Perhaps while it’s re-acquiring. Annoying. It also sucks out the battery charge pretty quickly. Leaving it on for about an hour took out 2/3’s the juice. May last longer if I turn off Wi-Fi and Bluetooth. That’s what I have to do to use my Golf GPS program to have it work for 5 hours. One nice thing is that even while you are scoping stuff, the phone still works OK simultaneously.
It was Jim Williams that noted it would be nice to have a way to take data and send it in an email so that is one cool thing. Me, I like a vertical knob and a horizontal knob. It took us a while to figure out that the time-base was varied the same way you zoom pictures on an iPhone. That is nice I guess, but I will keep my LeCroy and Tek scopes. This is too much of an expensive toy for me. You can get a pretty good used ‘scope for 300 bucks.