Handheld oscilloscopes, once thought of as baby cousins to bench models, now offer performance levels that rival those of their larger cousins while adding battery-powered operation and a portability not available in the bench instruments. To find out how this class of instruments—which cover a wide price range—stack up, I evaluated four models:

• AEMC OX 7104-C (100 MHz, four channels, $5995),
• Fluke 199C (200 MHz, two channels, $2999),
• Agilent Technologies U1604A (40 MHz, two channels, $1651), and
• Protek 860F (60 MHz, two channels, $1686).

Tektronix also offers a handheld oscilloscope, the THS730, but the company chose not to participate in the evaluation. For a signal source, I used an Agilent 33220A, a 20-MHz function generator.

All four oscilloscope models include a built-in digital multimeter (DMM) and all come with oscilloscope and DMM probes. All except the Fluke instrument include communications cables and software as standard features. They all provide measurements such as RMS voltage, peak-to-peak voltage, and frequency. All include some form of spectral analysis, and all except the Protek model include a data recorder.

The Agilent and Protek models are not only comparable in price, but their firmware and software led me to believe that they come from the same source. Thus, I’ll cover them together, pointing out similarities and differences.

AEMC’s Model OX 7104-C is the only four-channel handheld oscilloscope on the market. Its 12-bit resolution, 100-MHz bandwidth, and touch-screen display put it high on the performance list. To justify its $5995 price, you’d better need the portability (AEMC offers a two-channel version for $3995). If not, you can find plenty of bench oscilloscopes with comparable performance and price, but most have 8-bit resolution as opposed to AEMC’s 12-bit resolution.

Adapters for the AEMC oscilloscope let you mix and match scope and DMM channels.

AEMC’s AC mains adapter is large, but the power supply is inline. Thus, its standard AC plug covers only one space on a power strip. The oscilloscope end of the power cord has a four-prong plug that looks as though it plugs in more than one way. Fortunately, it doesn’t.

You can also use separate adapters that provide BNC jacks for connecting cables. I used one to connect a function generator to the oscilloscope. Another adapter provides banana jacks for DMM probes. That’s handy, because it lets you mix and match channels and thus connect oscilloscope probes, DMM leads, or accessories such as current probes to any channel. All other oscilloscopes in this evaluation have two oscilloscope channels and one DMM channel.

AEMC’s probes feature a light to help you find test points.

The harmonic analyzer display shows a signal’s spectrum harmonics to the 30th harmonic with a check box under each one. Tapping the check box lets you display amplitude and phase information for that harmonic. The screen also displays RMS amplitude and total-harmonic distortion on the signal.

AEMC’s SX-Metro software lets you import data from the OX 7104-C into a PC and operate the oscilloscope (in scope mode) remotely. I used the RS-232 connection first, and the PC quickly recognized the oscilloscope. Not so with the optional Ethernet link. I had to go into the Options menu in the SX-Metro software to change the IP address to match that of the scope. I kept getting a communication error on my PC, so I returned to RS-232 to evaluate the software.

The cover of the AEMC oscilloscope tends to pop off.

The AEMC OX 7104-C is a powerful instrument. Its bandwidth and resolution make it a viable alternative to some bench scopes, and its ability to mix and match oscilloscope and DMM inputs with its four channels is unique. The instrument has a few quirks, though, particularly when saving files for PC downloading, and its price is difficult to justify.

At half the price of the AEMC and nearly twice the price of the Agilent and Protek models, the Fluke 199C ScopeMeter boasts the highest bandwidth of the lot (200 MHz) and the highest sampling rate (2.5 Gsamples/s). Fluke pioneered the handheld oscilloscope market, and the 199C has come a long way from the original ScopeMeter. The 199C is far easier to use than its ancestors. The buttons are neatly organized—though slightly too close together—and the four soft keys are easy to understand.

The screen is the largest of the four models I evaluated. It looks bright and clear when used indoors, but the plastic cover is so shiny that you can’t see the traces outdoors because of reflections. The oscilloscope has a hand strap on its left side, but the strap can be moved to the right side, making this the only one of the four instruments that addresses the needs of lefties. Moving the strap, however, will cover the optical communications port. The Fluke oscilloscope also has the most rugged stand of the group, and it is the only one with a strap that lets you hang the instrument while in use.

The ScopeMeter has two dedicated buttons marked “Zoom” and “Replay.” The zoom button cuts the time/div in half, which gives you a quick 2X zoom of the waveform. The replay button gives you a link to the past, letting you view the last 100 screens in reverse chronological order. When you exit the replay feature, you lose the data, because the scope starts recording another 100 screens.

The Fluke recorder feature stands out. It has three modes, of which two are for the oscilloscope, not just for the DMM. The scope trend plot lets you record scope measurements such as Vpk-pk, VAC, rise time, and frequency. I used it to record Vpk-pk and frequency because they’re easy to change in the function generator. The Scope Record option lets you store a long string of scope acquisitions into the unit’s deep memory. The DMM recorder lets you plot a selected DMM measurement. I chose VRMS and produced a trend plot.

Trend plots let you look at long-term changes in a signal. The 199C will record data until its memory fills, then it compresses the data to free half the memory and thus double the unit’s capacity. Record size is 27,000 points per input. You can set the instrument to stop recording when the memory is full, and you can use the time/div button to increase or decrease the time/recorder screen.

The FlukeView software lets you take a snapshot of the instrument’s screen, but it doesn’t provide oscilloscope updates in real time. It also provides limited online control of the instrument—once you find that feature in the program’s Instrument menu. You can change mode (scope, meter, logger), and you can recall setups. You can operate the recorder to capture DMM measurements in real time as well as save setups, print, and log data to the PC. You can also get a spectrum display of an input signal after first downloading a waveform display.

The Fluke 199C is a powerful handheld oscilloscope. If you’re left-handed, it’s the one for you. Its hanging strap makes the instrument useful for electrical applications where you often need both hands free. The software is good for downloading data for offline storage and analysis. Perhaps the only drawback is the highly reflective screen cover.

AGILENT U1604A

PROTEK 860F

The user interface on both instruments uses four soft keys and a wheel. (I found Protek’s wheel easy to spin, but Agilent’s was difficult, often requiring two hands.) The soft keys let you set parameters such as oscilloscope vertical and horizontal scales, triggers, measurement functions, math, and utilities. One utility lets you enable or disable the instrument’s mini-USB connectivity port and the standard USB port for use with flash memory. You must navigate the utility menu to find the setting to enable the USB ports. With USB off, you’ll get no communications or flash-memory access.

Measurement functions include peak-to-peak, RMS, frequency, rise time, and fall time. You make a measurement by pressing the corresponding soft key and using the wheel to scroll through the choices. The math menu also lets you select FFT and a filtering window (Hamming, Hanning, Blackman, or rectangular), and you can get spectral plots in real time on the screen.

Pressing the Meter button brings up a blank screen with three soft-key options: Volt Meter, Ohm Meter, and Aux Meter. Pressing the aux meter (F3) key brings up choices for temperature, current, humidity, and pressure. For the voltmeter, you can choose from AC/DC, min/max, and relative measurements. To return to other meter functions, you must press the meter button, which brings you to the top of the meter menu; there’s no “back” button. Pressing the ohmmeter button gives you resistance, diode, continuity, and capacitance measurements. (I wouldn’t have expected to find capacitance buried under ohms, though.) You make your selection by repeatedly pressing the F1 key.

Protek (shown) and Agilent oscilloscopes let you connect to a PC and to a USB flash drive.

Both instruments let you save screens and waveform data to a USB flash drive. You can save screens in graphical formats for importing into reports, and you can save data in text format for importing into Excel or other software. You can also save screens in a proprietary format that you can open with the PC software.

The PC software on the two instruments is also strikingly similar, right down to the word “Horizon” over the horizontal scale (time/div) indicator. The software lets you take complete control of the instrument and get screen updates in real time. It also lets you view measurement parameters, save waveforms in digital form, and capture screens. Once you install the software and turn on each instrument’s USB function, you establish communications by clicking on the virtual power button.

There are, however, hardware, firmware, and PC software differences worth noting. Agilent provides buttons for vertical and horizontal screen settings. Protek makes you change all settings through menus. Agilent uses a color screen whereas Protek’s screen is monochrome, and the monochrome screen is easier to see in daylight than the color screens from Agilent, AEMC, and Fluke. Protek gives you 20 MHz more bandwidth than Agilent. Both companies offer 20-MHz and 40-MHz models, with Protek also offering a 60-MHz model. Agilent includes a logger function for recording DMM measurements. Protek doesn’t.

Agilent’s recessed connectors make it difficult to connect probes.

Although the oscilloscope BNC connectors are mounted on top of both instruments, Agilent’s case causes the connectors to be recessed. That makes it difficult to connect and lock the probes unless you have especially small fingers.

Protek’s power button gave me problems. It was somewhat sticky. I had to pull it out with my fingernails each time I turned the unit on or off. The first time I attempted to shut down the unit, the button stuck in the on position overnight and drained the battery.

Although the PC software (Agilent PC Link and Protek WaveLink) is nearly the same, the install procedures differ. With Protek, you simply run the setup routine. The drivers and oscilloscope application will easily install. Communication to the instrument was easy once I enabled the USB port.

Agilent’s PC software (left) and Protek’s PC software bear striking similarities, as do their firmware.

Agilent requires you to install the drivers separately. I was at first unable to get the Agilent U1604A to communicate with the PC. I believe the cause was the Protek driver, which uses the same files as Agilent. Several phone calls and e-mails to Agilent technical support failed. The solution: Reformat the PC’s hard drive to eliminate all Protek drivers. Even then, the Agilent installation was awkward. It’s easy to make a mistake and have the PC fail to communicate with the oscilloscope.

Given that the operations and prices of the Agilent U1604A and Protek 860F are strikingly similar, the choice comes down to the small differences. If you need PC connectivity, go with the Protek instrument until Agilent updates its software-installation procedure. You should also select Protek if you need to replace batteries in the field or if you need the additional 20-MHz bandwidth. If you insist on buttons for basic oscilloscope settings, a recorder function, a color display, or a handle, then choose the Agilent model.