pico Technology PicoScope 3425 User manual

Copyright © 2007 Pico Technology Limited. All rights reserved.
PicoScope 3425
User's Manual
ps3425.en-2
PC Oscilloscope

I
Contents
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
Contents
.....................................................................................................................................11 Introduction
...........................................................................................................................................1
1 Overview
...........................................................................................................................................1
2 Minimum PC requirements
...........................................................................................................................................2
3 Safety information
...........................................................................................................................................3
4 Safety symbols
...........................................................................................................................................3
5 FCC notice
...........................................................................................................................................3
6 CE notice
...........................................................................................................................................4
7 Legal information
...........................................................................................................................................5
8 Company details
.....................................................................................................................................62 Product information
...........................................................................................................................................6
1 Pack contents
...........................................................................................................................................6
2 Installation instructions
...........................................................................................................................................7
3 Connector diagrams
...........................................................................................................................................8
4 Connecting the oscilloscope
...........................................................................................................................................9
5 Specifications
...........................................................................................................................................10
6 What is a differential oscilloscope?
...........................................................................................................................................11
7 Overflow indicators
...........................................................................................................................................11
8 AC/DC coupling
...........................................................................................................................................11
9 Resolution enhance
.....................................................................................................................................123 Programmer's reference
...........................................................................................................................................12
1 Driver
...........................................................................................................................................12
2 Programming with the PicoScope 3000 Series
...........................................................................................................................................12
1 Voltage ranges
...........................................................................................................................................12
2 AC/DC coupling
...........................................................................................................................................12
3 Triggering
...........................................................................................................................................13
4 Sampling modes
...........................................................................................................................................16
5 Oversampling
...........................................................................................................................................16
6 Scaling
...........................................................................................................................................16
7 Combining oscilloscopes
...........................................................................................................................................17
8 Functions
...........................................................................................................................................51
3 Programming examples
...........................................................................................................................................51
1 C
...........................................................................................................................................52
2 C++
...........................................................................................................................................52
3 Visual Basic
...........................................................................................................................................53
4 Delphi
...........................................................................................................................................53
5 Excel
...........................................................................................................................................53
6 Agilent VEE
...........................................................................................................................................53
7 LabView
.....................................................................................................................................544 Troubleshooting
...........................................................................................................................................54
1 Software error codes
...........................................................................................................................................55
2 Driver error codes
.....................................................................................................................................565 Glossary

PicoScope 3425 PC OscilloscopeII
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..............................................................................................................................................59
Index

Introduction 1
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
1Introduction
1.1 Overview
The PicoScope 3425 PC Oscilloscope is a high-precision differential oscilloscope.
(What is a differential oscilloscope?) It is fully USB 2.0 -capable and
backwards-compatible with USB 1.1 . There is no need for an external power supply
as power is supplied from the USB port, making these oscilloscopes highly portable.
With the PicoScope software, the PicoScope 3425 can be used as a PC Oscilloscope
and spectrum analyser . Alternatively, using the API functions, you can develop
your own programs to collect and analyse data from the oscilloscope.
1.2 Minimum PC requirements
For the PicoScope 3425 PC Oscilloscope to operate correctly, you must connect it to a
computer with the minimum requirements to run Windows or the following (whichever
is the higher specification):
Processor
Pentium-class processor or equivalent minimum.
Memory
256 MB minimum.
Disk space
10 MB minimum.
Operating system
Microsoft Windows XP SP2 or Vista.
Ports
USB 1.1 compliant port minimum. USB 2.0 compliant port
recommended. Must be connected directly to the port or a
powered USB hub. Will not work on a passive hub.
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PicoScope 3425 PC Oscilloscope2
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1.3 Safety information
We strongly recommend that you read the general safety information below before
using your oscilloscope for the first time. If you use the oscilloscope in a manner
contrary to these instructions, safety protection built in to the equipment may cease
to function. This could cause damage to your computer or other equipment, or lead to
injury to yourself and others.
Maximum input range
The PicoScope 3425 PC Oscilloscope is designed to measure voltages in the range
stated in the Specifications table. The oscilloscope can withstand the Overvoltage
stated in the Specifications table, and operation with voltages exceeding this range
may cause physical damage.
Mains voltages and measurement category
The PicoScope 3425 PC Oscilloscope is designed only for CAT I measurements as
defined by BS EN61010-1:2001, which permits measurements on circuits that are
not directly connected to the mains (line power). The oscilloscope is not designed for
measurements on CAT II, III or IV circuits.
The PicoScope 3425 PC Oscilloscope must not be directly
connected to the mains (line power).
Failure to heed this warning may lead to injury or death.
Safety grounding
The PicoScope 3425 PC Oscilloscope connects directly to the ground of a computer
through the USB cable provided. This connection is intended only to minimise
interference, and therefore you must not rely on it as a protective safety ground.
Do not connect the ground sockets on the front panel to any source other than
ground. If in doubt, use a meter to check that there is no significant AC or DC
voltage between the oscilloscope's ground socket and point to which you intend to
connect it. Failure to check may cause damage to your computer, or injury to
yourself and others.
Repairs
The oscilloscope contains no user-serviceable parts. Repair or calibration of the
oscilloscope requires specialised test equipment and must only be performed by Pico
Technology.
Cleaning and decontamination
Remove all connections from the unit
Clean the external surfaces of the oscilloscope with a soft damp cloth. Do not use
chemical cleaners.
Make sure that the instrument is completely dry before using again.
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Introduction 3
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
1.4 Safety symbols
Symbol 1: Caution: risk of electric shock
This symbol indicates that a safety hazard exists on the indicated
connections if you do not take correct precautions. Ensure that you read
in detail all safety documentation associated with the product before using
it.
Symbol 2: Equipotentiality
This symbol indicates that the indicated connectors are all at the same
potential (i.e. are shorted together). You must therefore take necessary
precautions to avoid applying a potential across the indicated terminals as
this may result in a large current, causing damage to the product and
connected equipment.
1.5 FCC notice
This equipment has been tested and found to comply with the limits for a Class A
digital device,pursuant to Part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference when the equipment is
operated in a commercial environment. This equipment generates, uses, and can
radiate radio frequency energy and, if not installed and used in accordance with the
instruction manual, may cause harmful interference to radio communications.
Operation of this equipment in a residential area is likely to cause harmful interference
in which case the user will be required to correct the interference at his or her own
expense.
For safety and maintenance information see the safety warning .
1.6 CE notice
The PicoScope 3425 PC Oscilloscope meets the intent of the EMC directive
89/336/EEC and is designed to the EN61326-1 (1997) Class B Emissions and
Immunity standard.
The oscilloscope also meets the intent of the Low Voltage Directive and is designed
to the BS EN 61010-1:2001 / IEC 61010-1:2001 (safety requirements for
electrical equipment for measurement, control, and laboratory use) standard.
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PicoScope 3425 PC Oscilloscope4
Copyright © 2007 Pico Technology Limited. All rights reserved.ps3425.en
1.7 Legal information
The material contained in this release is licensed, not sold. Pico Technology Limited
grants a licence to the person who installs this software, subject to the conditions
listed below.
Access
The licensee agrees to allow access to this software only to persons who have been
informed of these conditions and agree to abide by them.
Usage
The software in this release is for use only with Pico products or with data collected
using Pico products.
Copyright
Pico Technology Limited claims the copyright of, and retains the rights to, all material
(software, documents etc) contained in this release. You may copy and distribute the
entire release in its original state, but must not copy individual items within the
release other than for backup purposes.
Liability
Pico Technology and its agents shall not be liable for any loss, damage or injury,
howsoever caused, related to the use of Pico Technology equipment or software,
unless excluded by statute.
Fitness for purpose
As no two applications are the same, Pico Technology cannot guarantee that its
equipment or software is suitable for a given application. It is your responsibility,
therefore, to ensure that the product is suitable for your application.
Mission-critical applications
This software is intended for use on a computer that may be running other software
products. For this reason, one of the conditions of the licence is that it excludes use in
mission-critical applications, for example life support systems.
Viruses
This software was continuously monitored for viruses during production, but you are
responsible for virus-checking the software once it is installed.
Support
If you are dissatisfied with the performance of this software, please contact our
technical support staff, who will try to fix the problem within a reasonable time. If you
are still dissatisfied, please return the product and software to your supplier within 28
days of purchase for a full refund.
Upgrades
We provide upgrades, free of charge, from our web site at www.picotech.com. We
reserve the right to charge for updates or replacements sent out on physical media.
Trademarks
Windows is a trademark or registered trademark of Microsoft Corporation. Pico
Technology Limited and PicoScope are internationally registered trademarks.

Introduction 5
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
1.8 Company details
You can obtain technical assistance from Pico Technology at the following address:
Address:
Pico Technology
James House
Colmworth Business Park
Eaton Socon
St. Neots
PE19 8YG
United Kingdom
Phone:
[phone]
Fax:
[phone]
Email:
Technical Support:
[email protected]
Sales:
[email protected]
Web site:
www.picotech.com

PicoScope 3425 PC Oscilloscope6
Copyright © 2007 Pico Technology Limited. All rights reserved.ps3425.en
2Product information
2.1 Pack contents
The PicoScope 3425 pack contains the following items:
Reorder code
Description
Quantity
PR090
PicoScope 3425 Differential PC Oscilloscope
1
MI106
USB cable, for use with USB 1.1 and USB 2.0 ports
1
TA039
Screened twisted-pair lead, 1.3 metre
4
TA038
Current clamp adaptor
4
TA001
Black test probe
1
TA002
Red test probe
1
TA005
Black dolphin clip
4
TA006
Red dolphin clip
4
DO115
Quick Start Guide
1
DI025
PicoScope software and reference CD
1
The accessories supplied with the PicoScope 3425 are rated for safe
working at the maximum voltages stated in the Specifications. For
your safety, if you use your own accessories with this oscilloscope, you
must ensure that they are rated for the voltage you are measuring.
2.2 Installation instructions
Important
You must install the PicoScope software before connecting
a PicoScope 3425 PC Oscilloscope to your PC for the first time.
Install the software by following the steps in the quick start guide supplied with your
oscilloscope. You can then connect your oscilloscope to the PC.
There is no need for an additional power supply, as the unit draws its power from the
USB port.
Checking the installation
Once the software has been installed, ensure that the oscilloscope is connected to the
PC and then start the PicoScope software. The software should now display the
voltage of any signal that is connected to the oscilloscope. If you are using the
differential cable and test probes supplied, you should see a small 50 or 60 hertz
noise signal in the oscilloscope window when you touch the test probes with your
fingers.
See Connector diagrams .
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2.3 Connector diagrams
Front view (3425)
Rear view
1. Ch A. Input channel A. As this is a differential oscilloscope, the channels have
non-standard input impedances and cannot be used with passive attenuated
scope probes such as the x1/x10 probes supplied with conventional oscilloscopes.
2. Ch B. Input channel B. Has the same characteristics as Ch A.
3. Ch C. Input channel C. Has the same characteristics as Ch A.
4. Ch D. Input channel D. Has the same characteristics as Ch A.
5. Ground. Can be used with the current clamp adaptor supplied to convert one or
more of the differential inputs to single-ended inputs. Can also be used to ground
the screen of the shielded twisted-pair cable supplied.
The scope's ground is connected to the PC's ground through the USB
cable. You MUST NOT rely on the scope's ground as a protective safety
ground.
6. LED. Lights up when the oscilloscope is first powered up, switches off when the
PicoScope software begins to run, and then flashes while the oscilloscope is
capturing data.
7. USB port. Compatible with USB 1.1 and USB 2.0 ports.
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PicoScope 3425 PC Oscilloscope8
Copyright © 2007 Pico Technology Limited. All rights reserved.ps3425.en
2.4 Connecting the oscilloscope
The oscilloscope is supplied with the following cables and adaptors:
TA038 Current clamp adaptor
TA039 Screened twisted-pair cable
TA038 Current clamp adaptor
Use this adaptor to connect a current clamp to the oscilloscope. First fit the adaptor
to one of the BNC inputs on the oscilloscope's front panel, then insert the adaptor's
grounding plug into one of the ground sockets on the front panel.
It is important to ground the current clamp using the procedure just described. Most
current clamps have an internal metal case that readily picks up electromagnetic noise
from the environment, and if the case were not grounded, this noise would interfere
with the signal.
TA039 Screened twisted-pair cable
Use this cable to connect a signal directly to the oscilloscope. A positive signal will be
displayed when you connect the red BNC plug to the more positive signal and the
black BNC plug to the more negative signal. If you connect these the wrong way
round, the oscilloscope will not be damaged but the signal will appear inverted on the
scope display.
Insert the grounding plug into one of the ground sockets on the front of the
oscilloscope. This grounds the screen of the cable to prevent it from picking up
electromagnetic noise that might otherwise interfere with the signal.

Product information 9
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
2.5 Specifications
Specification
Value
Vertical resolution
12 bits
Analogue bandwidth
5 MHz
(3 MHz on 100 mV range)
Channels
4
Maximum sampling rate
Single channel
Two channels
Three or four channels
20 MS/s
10 MS/s
5 MS/s
Capture memory
One channel enabled
Two channels enabled
Three or four channels enabled
512 k samples
256 k samples
128 k samples
Input type
Differential voltage
Selectable AC or DC coupling
Touch-proof BNC connectors with 4 mm GND sockets
Input impedance
12.4 MW(on 100 mV to 5 V ranges)
10.1 MW(on 10 V to 400 V ranges)
Input capacitance
12 pF
Common-mode voltage range
to ensure measurement accuracy
30 V (on 100 mV to 5 V ranges)
400 V (on 10 V to 400 V ranges)
Maximum safe voltages
Differential
Any input above scope GND
400 V
400 V (600 V transient)
Measurement category rating
CAT I
Voltage ranges
100 mV, 200 mV, 500 mV, 1 V, 2 V, 5 V,
10 V, 20 V, 50 V, 100 V, 200 V, 400 V
Accuracy
Voltage: ±1%
Time: 50 ppm
Linearity
12 bits
Noise
< 10 LSB
Operating environment
Temperature range
Humidity range
0 °C to 40 °C
(20 °C to 30 °C for quoted accuracy)
Minimum 5% RH non-condensing
Maximum 80% RH non-condensing,
decreasing linearly to 50% at 40 °C
Storage environment
Temperature range
Humidity range
-20 °C to 60 °C
5% to 90% RH non-condensing
Other environmental conditions
Dry environments
Altitude up to 2000 m
No pollution, or only dry, non-conductive pollution
PC connection
USB 2.0
Compatible with USB 1.1
Power supply
From USB port
4.6 V to 5.25 V DC @ approx. 500 mA
No external power supply required
Dimensions
255 mm x 170 mm x 40 mm
(approximately 10.0 in x 6.7 in x 1.6 in)
Weight
920 g (approximately 2 lb)
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2.6 What is a differential oscilloscope?
The PicoScope 3425 is a differential PC Oscilloscope. A differential oscilloscope
measures the voltage difference between two points, regardless of the voltage of
either point with respect to ground. This is unlike a conventional single-ended
oscilloscope, which requires one of the points to be at ground potential.
For example, suppose that you want to measure the output voltage of a transformer
with a grounded centre tap, as in the diagram below:
A single-ended oscilloscope can only measure a signal with reference to ground, so
you need to connect the scope's ground clip to the centre of the secondary. You can
then measure either VPor VNwith respect to ground, but not the total voltage across
the secondary. The diagram below shows a single-ended scope connected between VP
and ground:
With a differential oscilloscope, you can directly measure the secondary voltage by
connecting the positive probe to VPand the negative to VN. This is shown in the
diagram below. A ground connection is not essential, although it is a good idea to use
a shielded cable grounded at one end in order to prevent electromagnetic noise
coupling into the cable.
Differential oscilloscopes have many other applications where the voltage to be
measured is not referenced to ground, or where it is not desirable to connect the
scope ground to the ground of the device under test.

Product information 11
Copyright © 2007 Pico Technology Limited. All rights reserved. ps3425.en
2.7 Overflow indicators
PicoScope 6, the PC Oscilloscope software supplied with the PicoScope 3425, displays
a yellow common-mode overflow indicator for each channel when either the
positive or the negative input voltage with respect to ground is outside the range
stated in the Specifications. Exceeding the common-mode range of the scope
causes inaccurate measurements and can lead to severe signal distortion.
The red differential overflow indicator is used to warn when the differential
voltage (the difference between the positive and negative inputs) on each channel
exceeds the selected voltage range. This condition causes clipping of the displayed
signal.
2.8 AC/DC coupling
Each channel can be set to use either AC or DC coupling. When AC coupling is used,
any DC component of the signal below about 1 hertz is filtered out.
To change the coupling mode, select AC or DC from the control on the oscilloscope
toolbar of the PicoScope software. The setting should be chosen to suit the
characteristics of the input signal.
2.9 Resolution enhance
The hardware resolution of the oscilloscope is 12 bits, but you can obtain an effective
resolution of up to 16 bits using the Resolution Enhance feature built in to the
PicoScope software. See the PicoScope 6 User's Guide for details.
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3Programmer's reference
3.1 Driver
The Windows XP/Vista 32-bit driver, picopp.sys, is installed under the control of a
Setup Information File, picopp.inf.
Once you have installed the PicoScope and PicoLog software, Windows will
automatically install the driver when you plug in the PicoScope 3425 PC Oscilloscope
for the first time.
3.2 Programming with the PicoScope 3000 Series
The ps3000.dll library in your PicoScope installation directory allows you to
program a PicoScope 3425 oscilloscope using standard C function calls.
A typical program for capturing data consists of the following steps:
Open the scope unit
Set up the input channels with the required voltage ranges and coupling mode
Set up triggering
Start capturing data. (See Sampling modes for a more detailed discussion of
programming.)
Wait until the scope unit is ready
Copy data to a buffer
Stop capturing data
Close the scope unit
Numerous sample programs are installed with your PicoScope software. These
show how to use the functions of the driver software in each of the modes available.
3.2.1 Voltage ranges
It is possible to set the gain for each channel with the ps3000_set_channel()
function. This will give an input voltage range between ±100 mV and ±400 V.
3.2.2 AC/DC coupling
Using the ps3000_set_channel() function, each channel can be set to either AC or
DC coupling. When AC coupling is used, any DC component of the signal is filtered
out.
3.2.3 Triggering
PicoScope 3000 Series PC Oscilloscopes can either start collecting data immediately,
or be programmed to wait for a trigger event to occur. In both cases you need to
use the ps3000_set_trigger() function. A trigger event can occur on any of the
conditions available in the simple and advanced triggering modes.
Applicability
Available in block mode and fast streaming mode only. Calls
to the ps3000_set_trigger() function have no effect in
compatible streaming mode .
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3.2.4 Sampling modes
PicoScope 3425 PC Oscilloscopes can run in various sampling modes.
Block mode. At the highest sampling rates, the oscilloscope collects data much
faster than a PC can read it. To compensate for this, the oscilloscope stores a block
of data in an internal memory buffer, delaying transfer to the PC until the required
number of data points have been sampled.
Streaming modes. At all but the highest sampling rates, these modes allow
accurately timed data to be transferred back to the PC without gaps. The
computer instructs the oscilloscope to start collecting data. The oscilloscope then
transfers data back to the PC without storing it in its own memory, so the size of
the data set is limited only by the size of the PC's memory. Sampling intervals
from less than one microsecond to 60 seconds are possible.
3.2.4.1 Block mode
In block mode, the computer prompts a PicoScope 3425 PC Oscilloscope to collect a
block of data into its internal memory. When the oscilloscope has collected the whole
block, it will signal that it is ready and then transfer the whole block to the computer's
memory through the USB port.
The maximum number of values depends upon the size of the oscilloscope's memory.
A PicoScope 3425 can sample at a number of different rates. These rates correspond
to the maximum sampling rate divided by 1, 2, 4, 8 and so on.
There is a separate memory buffer for each channel. When a channel is unused, its
memory can be borrowed by the enabled channels. This feature is handled
transparently by the driver.
The driver normally performs a number of setup operations before collecting each
block of data. This can take up to 50 milliseconds. If it is necessary to collect data
with the minimum time interval between blocks, avoid calling setup functions between
calls to ps3000_run_block() , ps3000_ready() , ps3000_stop() and
ps3000_get_values() .
See Using block mode for programming details.
3.2.4.2 Using block mode
This is the general procedure for reading and displaying data in block mode:
1. Open the oscilloscope using ps3000_open_unit()
2. Select channel ranges and AC/DC coupling using ps3000_set_channel()
3. Using ps3000_set_trigger() , set the trigger if required
4. Using ps3000_get_timebase() , select timebases until the required number of
nanoseconds per sample is located
5. Start the oscilloscope running using ps3000_run_block()
6. Wait until the oscilloscope says it is ready using ps3000_ready()
7. Transfer the block of data from the oscilloscope using ps3000_get_values()
or ps3000_get_times_and_values()
8. Display the data
9. Repeat steps 5 to 8
10. Stop the oscilloscope using ps3000_stop()
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3.2.4.3 Streaming modes
The streaming modes are alternatives to block mode that can capture data
without gaps between blocks.
In a streaming mode, the computer prompts the PicoScope 3425 PC Oscilloscope to
start collecting data. The data is then transferred back to the PC without being stored
in oscilloscope memory. Data can be sampled with a period between 1 µs and 60 s,
and the maximum number of samples is limited only by the amount of free space on
the PC's hard disk.
There are two streaming modes:
Compatible streaming mode
Fast streaming mode
3.2.4.4 Compatible streaming mode
Compatible streaming mode is a basic streaming mode that works with all
scope units, at speeds from one sample per minute to a thousand samples per
second.
The oscilloscope's driver transfers data to a computer program using either normal or
windowed mode. In normal mode, any data collected since the last data transfer
operation is returned in its entirety. Normal mode is useful if the computer program
requires fresh data on every transfer. In windowed mode, a fixed number of samples
is returned, where the oldest samples may have already been returned before.
Windowed mode is useful when the program requires a constant time period of data.
Once the oscilloscope is collecting data in streaming mode, any setup changes (for
example, changing a channel range or AC/DC setting) will cause a restart of the
data stream. The driver can buffer up to 32 K samples of data per channel, but the
user must ensure that the ps3000_get_values() function is called frequently
enough to avoid buffer overrun.
See Using compatible streaming mode for programming details.
Applicability
Does not support triggering .
The ps3000_get_times_and_values() function will always
return FALSE (0) in streaming mode.
3.2.4.5 Using compatible streaming mode
This is the general procedure for reading and displaying data in compatible streaming
mode :
1. Open the oscilloscope using ps3000_open_unit()
2. Select channel ranges and AC/DC switches using ps3000_set_channel()
3. Start the oscilloscope running using ps3000_run_streaming()
4. Transfer the block of data from the oscilloscope using ps3000_get_values()
5. Display the data
6. Repeat steps 4 and 5 as necessary
7. Stop the oscilloscope using ps3000_stop()
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3.2.4.6 Fast streaming mode
Fast streaming mode is an advanced streaming mode that can transfer data at
speeds of a million samples per second or more, depending on the computer's
performance. This makes it suitable for high-speed data acquisition, allowing you
to capture very long data sets limited only by the computer's memory.
Fast streaming mode also provides data aggregation , which allows your application
to zoom in and out of the data with the minimum of effort.
Applicability
Works with triggering
See Using fast streaming mode for programming details.
3.2.4.7 Using fast streaming mode
This is the general procedure for reading and displaying data in fast streaming mode:
1. Open the oscilloscope using ps3000_open_unit()
2. Select channel ranges and AC/DC switches using ps3000_set_channel()
3. Set the trigger using ps3000_set_trigger()
4. Start the oscilloscope running using ps3000_run_streaming_ns()
5. Get a block of data from the oscilloscope using
ps3000_get_streaming_last_values()
6. Display or process the data
7. If required, check for overview buffer overruns by calling
ps3000_overview_buffer_status()
8. Repeat steps 5 to 7 as necessary or until auto_stop is TRUE
9. Stop fast streaming using ps3000_stop()
10. Retrieve any part of the data at any time scale by calling
ps3000_get_streaming_values()
11. If you require raw data, retrieve it by calling
ps3000_get_streaming_values_no_aggregation()
12. Repeat steps 10 to 11 as necessary
13. Close the oscilloscope by calling ps3000_close_unit()
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3.2.5 Oversampling
When the oscilloscope is operating at sampling rates less than the maximum, it is
possible to oversample. Oversampling is taking more than one measurement during
a time interval and returning an average. If the signal contains a small amount of
noise, this technique can increase the effective vertical resolution of the
oscilloscope by the amount given by the equation below:
Increase in resolution (bits) = log (oversample) / log (4)
Applicability
Available in block mode only
3.2.6 Scaling
The PicoScope 3425 PC Oscilloscope has a resolution of 12 bits, but the oscilloscope
driver normalises all readings to 16 bits. This enables it to take advantage of noise
reduction from oversampling , when this is enabled. The following table shows the
relationship between the reading from the driver and the voltage of the signal.
Constant
Reading
Voltage
PS3000_LOST_DATA
-32 768
Indicates a buffer overrun in fast streaming
mode.
PS3000_MIN_VALUE
-32 767
Negative full scale
0
0
Zero volts
PS3000_MAX_VALUE
32 767
Positive full scale
3.2.7 Combining oscilloscopes
It is possible to collect data using up to four PicoScope 3000 Series PC Oscilloscopes
at the same time. Each oscilloscope must be connected to a separate USB port. If
a USB hub is used it must be a powered hub. The ps3000_open_unit() function
returns a handle to an oscilloscope. All the other functions require this handle for
oscilloscope identification. For example, to collect data from two oscilloscopes at the
same time:
handle1 = ps3000_open_unit()
handle2 = ps3000_open_unit()
ps3000_set_channel(handle1)
... set up unit 1
ps3000_run_block(handle1)
ps3000_set_channel(handle2)
... set up unit 2
ps3000_run_block(handle2)
ready = FALSE
while not ready
ready = ps3000_ready(handle1)
ready &= ps3000_ready(handle2)
ps3000_get_values(handle1)
ps3000_get_values(handle2)
Note: It is not possible to synchronise the collection of data between oscilloscopes
that are being used in combination.
58
13
11
15
57
18