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Do we really have to send it back? Agilent MSO7034A Mixed Signal Scope 18  Silicon Chip siliconchip.com.au The MSO7034A from Agilent Technologies is a mixed signal oscilloscope. What does that mean? You get the best of both worlds: four analog channels as well as 16 digital inputs. Review by Mauro Grassi W e have to say that visually, the MSO7034A is very impressive, boasting a 12.1-inch XGA (1024 x 768 pixels) colour screen and a fast overall response, including a waveform update frequency of up to 100kHz and deep memory of 8Mp (Mega points). With a bandwidth of 350MHz and real time sampling rate up to 2GS/s, the MSO7034A is more than adequate for all but the most demanding applications. The MSO7034A is one of Agilent’s new 7000 series of scopes. It has standard connections that make it easily programmable, is network enabled and supports the new LXI standard for instrument control intended to supersede GPIB. This scope easily adapts to more specialised tasks such as FlexRay decoding and spectrum analysis, using optional accessories (both hardware and software). More on all these features shortly. Let us review the many standard features first. Holding down a key displays a help screen explaining its current function. The hierarchical menu system is not too complex and a horizontal row of soft keys allows easy navigation through the menus. Most settings can be changed with the SELECT knob, which illuminates when relevant. The value of the setting can be seen as it is being updated. Important settings controlling the vertical scale of each analog channel and the timebase, for example, have their own dedicated knobs. We should mention that this scope has surprisingly few settings that can be modified. For example, there is limited control of the appearance of the traces on the screen. The traces seem to be rendered too thickly in some cases and although this can be overcome by using the high-resolution mode (or the averaging function), it would be nice to let the user have finer control of the graphical rendering. We would like to see more user options in Specs at a glance Overview future versions of the Analog Input Channels: ................................ firmware to allow for The screen of the ..............................Four Digital Input Channels:........................................ this. Perhaps two differMSO7034A is as big ........................... 16 ent user modes could be as found in some Analog bandwidth: ........................................ ........ ....... DC - 350MHz implemented, one a simnotebook computSampling Rate: .............................................2G S/s for each channel plified version (with the ers. The high resMemory depth: ................ 4Mpts (four channels) most common options olution and size 8Mpts (2 channels) Verti cal Resolution: ................................................ and settings) and the make it pleasant to .................. 8 bits LCD display: ............. 12.1 inch colour TFT (XGA other a full version of the use with variable 1024 x 768 pixels) menu system with more intensity for traces Size (WxHxD):....................454 x 277 x 173m m with legs contracted options for controlling and the grid adding Weight: ................................................................ .................... 5.9 kg the look and behaviour of to its appeal. the scope. The downside The firmware can be to this, of course, programmed easily using any PC, so the firmware features is that the scope must be physically large enough to accan be upgraded as they become available. commodate the display. However, it is light for its size at less than 6kg. Four Analog Channels Another desirable quality of this scope is its very quiet Most of the time, you would use the AUTOSET feaoperation, unlike some other scopes with noisy cooling ture that chooses optimal settings, according to the input fans. signals. This is handy if you wish to view a signal on the It has a very attractive layout with illuminated buttons screen with minimum effort. and digital knobs. Each of the four analog channels has its Each analog channel can be AC or DC-coupled with own vertical scale knob and offset with the vertical resoluselectable input impedances of 50W or 1MW. The input tion of each channel reaching up to 12 bits (depending on impedance and coupling are indicated for each channel with the settings). At worst it is 8 bits. a white and yellow LED, the white LED spelling “AC” if the channel is currently AC coupled, while the yellow LED Accessibility Settings indicates a 50W input impedance. Moreover, each channel On-screen windows, showing the current settings of has its own LED to indicate if it is bandwidth limited, which the knobs, appear when they are activated (a window also increases the accuracy of the trace by reducing spurious informs you when the knob has reached its current limit). high frequency noise. This should be used whenever posThis scope has been designed with accessibility in sible for lower frequency signals. The bandwidth limiting mind, as evident by the context sensitive multi-language is user selectable up to 25MHz. help system. siliconchip.com.au July 2008  19 For the four analog channels, the vernier option allows the channel’s vertical knob to adjust the scale in smaller increments than the usual 1-2-5 scale, enabling better use of the available screen area. The vernier scale was used in the screen grab shown in Fig. 3. The BNC sockets accepting each analog channel also accommodate automatic sensing probes. Both the usual passive probes as well as active probes can be used. For passive probes, the scope can be calibrated to de-skew its capacitance, while active probes have in built amplifiers meaning their capacitance can be kept very low. The latter is desirable to ensure high input impedance even at high frequencies. As well as voltage sensing probes, this scope can accommodate current sensing probes, with the units for the vertical scale of each channel accommodating both Volts and Amperes. The probe attenuation can be set as high as 1000:1 meaning that potentials as high as 30kV can be measured. However, the vertical scale division on a 1:1 probe setting is at most 5V/div, which is on the low side and about the minimum you would want. Maths Functions and Labelling A close-up of the driver’s panel – we found it to be not only very logical and quite easy to use but also found a huge range of integrated help information available simply by pressing and holding any of the buttons. The MSO7034A has the usual mathematics functions including subtract, multiply, integrate, square root and differentiate, as well as the usual Fourier transform. The result is superimposed on the screen as a separate “MATH” trace, as can be seen in Fig. 4. One of the best features is that the result of the maths function can be measured in the same way as any other channel. One can measure, say, the average of an integral (useful for total power measurements), or measure the current through a resistor by using the difference between two voltage measurements (if you don’t have a current sensing probe). We would like to see even more flexibility in the maths functions in future models, including possibly a more Fig.1: the blue trace shows a TTL-level RS-232 data stream. Real time serial decoding is enabled (must be purchased separately) showing the hexadecimal values of the bytes transmitted. The baud rate is set at 115.2kbps with 8 bits per byte and no parity bit. The stream is the output of a microcontroller which is sending commands to an embedded LCD display. The op-code 0x3C corresponds to the command to write a character and the ASCII character follows. Fig.2: the output of a crystal oscillator circuit, an approximately sinusoidal waveform at 20MHz, forming the clock signal for a microcontroller, can be seen as the green trace. The frequency measurement shows 20MHz while the 5 digit frequency counter shows 20,003kHz. The bottom half of the window shows closer detail of the waveform using the zoom feature. The bottom window corresponds to the unshaded area in the top window. The shaded area is user selectable. 20  Silicon Chip siliconchip.com.au general mode where an arbitrary maths expression (within limits) can be defined by the user (however, this would probably add complexity to the hardware). The MSO7034A is a mixed signal oscilloscope, meaning it accepts digital signals as well as the four analog channels. Up to 16 digital traces can be displayed at any one time and Fig. 6 shows an example. Traces on the screen, including all 16 digital traces, can be given alphanumeric labels. This makes the display more intelligible – while the method of entering alphanumeric strings is rather awkward, requiring many presses and turns, it does not need to be done often enough to warrant having a keyboard. The inconvenience is mitigated by having a library of standard labels like IRQ, CLR, INT, etc. Moreover, the library labels can be used as templates by editing them to form new labels. Acquisition and Triggering The peak detect mode on the MSO7034A can detect short peaks down to half a nanosecond. In the averaging acquisition mode, up to 65536 (216) sweeps can be averaged to reduce noise and reveal the general trend of the waveform. The scope has comprehensive triggering modes encompassing the latest video formats for HDTV including 1080i, 1080p, 720p as well as standard video triggering for NTSC, SECAM, PAL and PAL-M video signals. Fig. 5 shows a typical standard definition PAL signal with TV triggering enabled. In addition to these triggering modes, there are serial triggering modes for I2C, SPI, USB and UART/RS232 modes, to list only the most common. For automotive applications, the standard triggering modes include CAN, LIN and FlexRay (FlexRay is the newest automotive serial protocol). An optional licence can be purchased to allow the scope to decode these serial streams. See the protocol analyzer section below for more details. Fig. 3: the trace shows the discharging of a capacitor through a resistor. The rise time is measured to be 1.06ms and the dashed orange lines show the points between which the rise time is measured. The capacitor used was a 1mF electrolytic connected in series with a 680W resistance. Notice that the vernier option has been used in setting the vertical scale. It stands at 800mV per division. The horizontal scale is 1ms/div. siliconchip.com.au In keeping with the four channels, the scope includes four high quality 500MHz probes. The other leads in this shot are 16 the digital input connectors. Quick Measurements 23 automatic measurements can be made with up to four measurements being displayed on the screen at a time. Cursors shown as dashed orange lines automatically track the most recently selected measurement. The is a feature we have not seen on other scopes. While useful for making sense of the displayed measurements and correlating the quantities with points on the waveform, the cursors cannot be disabled (in the current version of the firmware). This would be another desirable option since these indicators can detract from the intelligibility of the waveform, especially when the waveform is rapidly changing and the cursors become distracting. There is also a five-digit frequency counter whose accuracy can be increased to eight digits by using a stable 10MHz external reference signal. The frequency counter is shown in the screen grab in Fig.2. Protocol Analyzer The MSO7034A can be upgraded with a software licence that implements real-time serial decoding. For example, Fig.1 shows a RS232 stream being decoded by the scope. Serial decoding is very useful for debugging purposes, giv- Fig. 4: screen grab showing an approximate square wave at around 155kHz (yellow trace) with its computed FFT (pink trace). The peaks at the odd harmonics can be clearly seen. Four measurements of the square wave are shown towards the bottom of the screen, including RMS, frequency and maximum and minimum values. The minimum measured voltage level of –150mV is indicated by the dashed orange line. July 2008  21 ing a read-out of the hexadecimal or binary representation of the signal. Currently supported protocols include I2C, SPI, UART/RS-232, USB, FlexRay, CAN and LIN. Options A very good feature of this scope is that it is highly customisable, with optional accessories, as well as the serial decode licence mentioned previously. This allows the scope to be upgraded according to need. One significant upgrade is support for segmented memory, useful for high frequency pulsed applications like radar or sonar. It allows the acquisition memory to be effectively used for the relevant detail in the waveform (that is, the pulses) instead of being wasted on the relatively long interim periods when there is no interesting signal to speak of. (Segmented memory is an optional accessory that can be purchased separately). Another useful optional accessory is the power measurement suite. The software, installed on a PC, allows the scope to function as a very fast acquisition engine and allows power analysis using your PC. Many other accessories can be purchased separately to allow for different applications such as spectrum analysis and current sensing. The LAN port is extremely useful. It allows the scope to be addressable on a network and thanks to the LXI compliance, the scope has an in built web server. As such, it can be accessed using any common web browser with the familiar features of any HTML page. A full IO library software suite is included to allow automation and advanced applications may make use of this library. As previously mentioned, the firmware of the scope can be upgraded via a PC. Considering that a scope can have an operational life of many years, this is a must for any serious purchase as it allows features to be upgraded in the future and any bugs to be corrected. Conclusion The MSO7034A scope has standard connections for USB, including two host ports and one device port, LAN, XGA video out (for connection to a monitor) and is LXI class C compliant. LXI is the new LAN-based standard for instrument control, intended to supersede GPIB. One minor criticism of the USB host ports is that they are only version 1.1; they really should be version 2.0 to bring them in line with current standards, as version 1.1 is all but obsolete. Although the speed of version 1.1 is adequate for most purposes, it would be better to have the luxury of the highest speed of the USB. The USB device port is of course version 2.0. The Agilent MSO7034A is an impressive mixed signal scope and has everything you would expect from a higher end scope. It is surprisingly fast and responsive and the display is exceptional. With a recommended retail price of $14,377 (ex. GST) including a 3 year warranty, it is available from Agilent agents, Trio Smartcal. This gets you the scope, a calibration certificate, four analog probes, a digital 16 channel connector with clips, user manual, PC software including IO library and hard plastic front cover. Serial decode licences can be purchased separately for $1550 (ex. GST). A DSO-only equivalent model, the Agilent DSO7034A, is available for $11,229 (ex. GST), also from Trio Smartcal. The DSO version can later be upgraded to the MSO version by purchasing a software licence. See www.triosmartcal.com.au or phone Trio Smartcal on 1300 853 407 for more information. And do you want to know the really good news? He who controls the purse strings (among other things) around here heard how much I liked this scope. So a deal was done – and we’re now the proud owners of a brand new Agilent! SC Fig. 5: the top half of the window shows a PAL video test signal composed of coloured vertical columns (green trace). The unshaded area is magnified and shown in the bottom half of the window. The detail shown corresponds to the colour burst sequence. PAL triggering is used and some measurements are displayed, including the minimum and maximum levels and the frequency of 15.63kHz which is very close to the PAL horizontal frequency. Fig. 6: this screen grab shows 8 digital waveforms captured by the scope on the digital channels D0-D7. The selected triggering mode is shown in icon form at the top right corner of the window. It indicates that the acquisition on all channels is triggered by either a rising or a falling edge on the first digital channel. Two cursors are shown as vertical dashed orange lines, and the logical value at the cursors is shown as a hexadecimal byte. Standard Connections 22  Silicon Chip siliconchip.com.au