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ELAN DIGITAL SYSTEMS LTD.
LITTLE PARK FARM ROAD,
SEGENSWORTH WEST,
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HANTS. PO15 5SJ.
TEL: (44) (0)1489 579799
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USBscope50
USER’S GUIDE
ES370
Important Notice: Please refer to Safety Data 4.4.1, before using this instrument
All Trademarks are duly acknowledged.
The USBscope50 is Patent Pending.
REVISION HISTORY
ISSUE PAGES DATE NOTES
1 30 04.07.2005 FIRST ISSUE
2 30 08.07.2005
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CONTENTS 1 OVERVIEW................................................................................................5 2 ABOUT THE USBSCOPE50 .....................................................................6 2.1 General ............................................................................................................ 6 2.2 USBscope50 Architecture .............................................................................. 7 2.3 Using More Than One USBscope50................
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4 HARDWARE SPECIFICATION ............................................................... 36 4.1 Power Requirements .................................................................................... 36 4.2 Mechanical .................................................................................................... 36 4.3 Environmental .............................................................................................. 36 4.4 Performance...........................................
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Disclaimer This document has been carefully prepared and checked. No responsibility can be assumed for inaccuracies. Elan reserves the right to make changes without prior notice to any products herein to improve functionality, reliability or other design aspects. Elan does not assume any liability for loses arising out of the use of any product described herein; neither does its use convey any license under its patent rights or the rights of others. Elan does not guarantee the compa
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1 OVERVIEW The USBscope50 is a digital storage oscilloscope that has the following features: • Single channel scope with BNC input and USB PC interface • Each USBscope50 can be stacked to increase channel count (each 1 requires its own USB connection) 2 • 300V Cat II isolation between BNC ground and USB ground • 50MSample/sec single shot sample rate 3 • 1GSample/sec equivalent sample rate • Timebase from 4ns/div to 4s/div in 1,2,4 steps 4 • 75MHz 3dB analogue bandwidth • 3000 sam
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2 ABOUT THE USBscope50 2.1 General The USBscope50 uses a 50MSample/sec 8-bit A-to-D converter. The A-to-D and front-end circuits that process the input waveform, and the digital stages that acquire and store the waveform are all powered from the USB host interface via an isolated supply. This means that there is no galvanic connection between the BNC ground (or BNC centre terminal), and the USB interface. When you measure a circuit and connect the scope ground clip to a voltage that
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2.2 USBscope50 Architecture The figure below shows a simplified diagram of the USBscope50. STACK AC/DC CONN CONTROLLER BNC USB USB COMP Trigger CONTROLLER DATA ATTENUATOR AMP 8-BIT ADC 1Meg PSU ISOLATION BARRIER Figure 2.2-1 USBscope50 Architecture Diagram Elan Digital Systems Ltd. 7 USBscope50 USER’S GUIDE Iss5
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2.3 Using More Than One USBscope50 A unique feature of the USBscope50 architecture is that up to 4 7 devices can be stacked to make a multi-channel instrument. In order to use a stacked configuration, you must purchase the stacking connector kit. This kit comprises 3 long lead connectors and 1 short lead connector as shown: 2.3.1 Assembling The Stack To stack the USBscope50 devices, first be sure that none of them are connected to a USB port. Before you begin, put the short l
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Repeat this for all except the last scope to be stacked. For the last scope in the stack, do the same as above but use the short length connector. This time, the pins are shorter so they stop well inside the scope’s case. This scope MUST be the bottom scope in the stack. The reason for this is that if you use the long connector, the pins could be shorted out accidentally, or you may touch the pins when the scope is connected to a high voltage and you could get an electric shock!
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Start with the bottom scope. Hold it in one hand, and put the next st scope on top of the 1 , the same way around. Align the stacking connectors and when the stacking connectors are partly mated nd engage the front “P” shaped clip (BNC end) on the 2 scope into the st “P” shaped slot on the 1 scope. nd Now, bring the back edge “P” clip (USB end) of the 2 scope down st until it clicks into the 1 scope’s slot. These two scopes are now mated. nd Check that as you pushed the 2 scop
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2.3.3 USB Connections For Stacked Configurations All stacked scopes need a USB connection. A standard hub may be useful for multi-channel stacks to get enough USB ports. Each scope needs about 200mA. Plugging more than 2 scopes into a hub will mean that the hub may need to be powered externally. Please refer to the hub’s documentation for more details about the power available per port. 2.3.4 Software For Stacked Configurations When you run USBscope50, it will automatically detect
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Repeat this for each channel in the stack to identify them. If you like, you can stop the software, and unplug all the scopes from their USB connections, and then re-stack them in their channel order. The “about” tab lists all the scopes that have been found. Click on any of the scopes in the list to see more information and an explanation of items in the list. Elan Digital Systems Ltd. 12 USBscope50 USER’S GUIDE Iss5
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2.3.5 Stacking Do’s And Don’ts • Do power off all scopes (remove USB lead) before connecting and disconnecting scopes from the stack • Don’t remove any scopes from the stack while the software is running • Don’t remove any scopes from the stack while any of them are powered • Don’t stack several scopes and leave one or more scopes un- stacked…this configuration will ignore the un-stacked scopes • Don’t short circuit any of the stack connector pins, or bend the pins or use excessive forc
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2.4 Input Ranges The USBscope50 supports 3 settings on its input attenuator. The ranges at the BNC input depend on the type of scope probe used: A “x1” probe causes no signal attenuation and will result in nominal full-scale input ranges of +/-0.3V, +/-3V and +/-30V. The bandwidth of x1 scope probes is generally quite low (10’s of MHz) and the circuit being measured will see a 1MegOhm load. A “x10” probe causes a factor of ten signal attenuation and will result in nominal f
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2.5 Probe Compensation Before taking measurements with the USBscope50, the attached x10 scope probe must be compensated to ensure that it is matched to the 8 scope input stage . This ensures that the probe+scope act together to keep the input frequency response as flat as possible. Using a scope probe that has not been adjusted to match the USBscope50 can lead to inaccurate readings for higher frequency signals. 9 The USBscope50 includes a probe compensation output . This mus
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2. Set the input range to 0.3V/div, x10 probe and coupling to AC 3. Use the channel tab and click on the “cmp” button to turn on the compensation output 4. Set the timebase to 100us/div, and set “auto” triggering, with the trigger level set to about 0%. 5. Now connect your probe tip to the compensation output on the scope. You should see a square wave something like this or it may look more like this 6. You may find you need to connect the ground clip to either the BNC ground
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12 output to achieve a clean waveform with minimal mains “hum” 7. Now, slowly adjust the trimmer in the probe body until you achieve the best square wave shape that you can. By this we mean nice square corners and minimum over and under shoot near the edges. A small amount of over shoot is preferable to an adjustment with “curved” square wave corners: this would mean that the scope will attenuate high frequency signal components whereas a small amount of overshoot will mean that the s
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2.6 Acquisition Modes The USBscope50 can acquire waveforms in two different ways. The mode and sample interval (i.e. the time between each data point) is displayed on the main panel 2.6.1 Single Shot In this mode, the ADC is clocked at up to 50MegaSamples/sec. Each sample is placed into the buffer and then the buffer is painted on the screen. This mode is the one to use for non-repetitive signals i.e. single pulses, irregular bus events etc. It can also be used for repetitive
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2.6.2 Random Interleaved Sampling This mode is a little more complex and is suited only to observing certain types of waveform. The USBscope50 includes special circuitry that allows it to trigger off the input waveform and also to be able to measure the time between the trigger instant and the first ADC sample that is taken. In this way, several single shot acquisitions are taken and the data points for each “sweep” are ordered based on the relative time as measured. For this to work
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RIS mode is not well suited to very slow input signals or signals that have jitter. This will lead to an uncertainty in the trigger instant and hence the sweep data will appear in the wrong “bins” and so the displayed waveform will not “lock” on the screen over time. Please note that in RIS mode it is not possible to observe the probe compensation output. This is because it is precisely phase- locked to the ADC’s clock hence there is no way to take random sweeps to build up the picture
