$199 wireless oscilloscope needs a few enhancements

-October 05, 2017

Over the past several years, we at EDN have seen a proliferation of offbeat oscilloscopes. They plug directly into iPhones and iPads, connect over WiFi, fit in your pocket, hold an iPad, and wrap around your wrist. At $199, the Aeroscope 100A comes in just under $200, which is critical for makers and hobbyists. With a few more software features, the Aeroscope 100A would certainly be worth the money.

This single-channel, 20 MHz, 100 Msample/s pen-shaped instrument connects to iOS phones (4S or later) and iPads (3 or later) over a Bluetooth Low Energy (BT 4.0) connection. That's enough for you to remotely monitor a machine or walk around and show others the signals on your circuits. The pen-shaped design is easy to hold or mount.

[Try an oscilloscope for under $200]

When Aeroscope engineers Jonathan Ward and Alexander Lee first showed their prototype, they had planned to give it 100 MHz of bandwidth. Alas, the cost of the A/D converter drove the price too high so they backed off on bandwidth to meet the sub-$200 price. Smart move, for any oscilloscope over $200 puts it out of reach of many makers, hobbyists, and engineers working on home projects. With 20 MHz of bandwidth, the Aeroscope 100A lets you troubleshoot many IoT devices, look at low-speed buses, and view audio signals.

The Aeroscope 100A comes in a nearly pocket-size pouch (Figure 1). It comes with a pen probe that screws onto the tip through an SMA connector and has a clip-on ground lead. That's good for troubleshooting, but not for monitoring. Fortunately, you also get a set of mini-grabbers when you need hands-free operation. What you don't get is a battery charger and micro-USB charge cable, but you probably have plenty of those anyway.

Figure 1. The Aeroscope comes with both a probe tip and clip leads.

Getting started with the Aeroscope 100A is easy. Simply download and install the app for your iOS or android device. I used an iPhone 6 because Aeroscope doesn't support my iPad 2.

Connecting devices over Bluetooth can sometime be challenging, but not with the Aeroscope app. It does all the work for you. No manual pairing devices—it just worked.

Operating the Aeroscope 100A was also easy. A simple menu screen provides access to the oscilloscope functions such as triggering and normal/auto/single capture. Just look for the menu icon to bring up the options (Figure 2).

Figure 2. A few easy touches get you to functions such as VMAX and VPK-PK.

Because the Aeroscope 100A has only one channel, there's no need for channel math—addition, subtraction, etc. But, I would have liked to see cursors, frequency measurement, FFT, and a pulse-width trigger. There's also no auto setup feature, something we've come to expect in all oscilloscopes. Furthermore, there doesn’t appear to be any way to record measurements other than to take screen images. Perhaps a future version of the app will add those features.

Here's a minor thing with the app. Look at the top of the screen in Fig. 2. It reads "5us/div." Sure, we all know that means five microseconds per division, but it should read "5µs/div." In the video below, I walk you through the operation of the Aeroscope 100A.

Bandwidth tests
How does the Aeroscope 100A stand up against a 100 MHz oscilloscope with a typical 150 MHz probe? To find out, I tried a 5 VPK-PK sine wave at frequencies from 100 kHz to 10 MHz on the Aeroscope and a $2000 National Instruments VirtualBench. Why not go to the full 20 MHz bandwidth? Because I was using the Aeroscope's mini-grabbers, for which the bandwidth isn’t specified but we can assume stray capacitance takes its toll. Even with a 100 MHz oscilloscope and a 150 MHz probe.

Frequency Aeroscope amplitude (VPK-PK) VirtualBench amplitude (VPK-PK)
200 kHz 5.02 V 4.925 V
500 kHz 5.02 V 4.925 V
1 MHz 5.02 V 4.925 V
2 MHz 5.02 V 4.925 V
5 MHz 4.94 V 4.80 V
10 MHz 4.83 V 4.5 V

Next, I tried a 5 MHz square wave. The trace in Figure 3 shows the beginnings of ringing, which again I attribute to parasitic capacitance and inductance in the mini-grabbers. At 10 MHz, the ringing becomes more pronounced and VPK-PK drops considerably (Figure 4). Ringing and amplitude drop were far less pronounced when looking at them on the VirtualBench. So, if you want to use the Aeroscope 100A at frequencies above roughly 2 MHz, you should make your own probe with an SMA connector to attach it to the instrument. Just make sure that your probe works with the Aeroscope 100A's 1 MΩ input impedance.

Figure 3. A 5 MHz square wave shows some ringing.

Figure 4. At 10 MHz, VPK-PK drops to 3.42 V because of stray capacitance and inductance in the mini-grabber probes.

Based on my measurements, you can see that having the 100 MHz bandwidth that Lee and Ward originally designed wouldn't have improved performance, but it would have increased the price to unacceptable levels about $200.

The Aeroscope 100A is a useful tool for home projects and for mounting in a device to monitor performance. At $199, it won’t break the bank. With a few more features in the app such as frequency measurement, FFT, auto setup, cursors, and data recording it will be more appealing.

Martin Rowe covers test and measurement for EDN and EE Times. Contact him at martin.rowe@AspenCore.com Follow me on TwitterVisit my LinkedIn page

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