pico Technology ADC-20 User manual

ADC-20/ADC-24
High-Resolution Data Loggers
User's Guide
adc20.en r6
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved.

I Contents
Contents
1 Introduction ................................................................................................................................ 1
1 Overview ............................................................................................................................................ 1
2 Notices ....................................................................................................................................... 2
1 Safety warning .................................................................................................................................... 2
2 Legal information ............................................................................................................................... 2
3 CE notice ............................................................................................................................................ 3
4 FCC notice ......................................................................................................................................... 3
5 Trademarks ........................................................................................................................................ 3
6 Updates ............................................................................................................................................. 3
7 Support and refunds ........................................................................................................................... 4
3 Getting started ............................................................................................................................ 5
1 Installing the software ......................................................................................................................... 5
2 Connecting the data logger ................................................................................................................. 5
3 Starting PicoLog ................................................................................................................................. 5
4 About the unit ............................................................................................................................ 8
1 Introduction ....................................................................................................................................... 8
2 Specifications ...................................................................................................................................... 8
3 Analog connector ............................................................................................................................. 10
4 Noise-free resolution and conversion time ......................................................................................... 11
5 ADC-20/ADC-24 terminal board ....................................................................................................... 11
6 LED .................................................................................................................................................. 11
5 Programmer's reference ........................................................................................................... 12
1 Recording methods ........................................................................................................................... 12
2 Windows driver ................................................................................................................................ 12
3 Scaling .............................................................................................................................................. 12
4 Driver functions ................................................................................................................................ 13
1 HRDLCloseUnit .................................................................................................................... 14
2 HRDLCollectSingleValueAsync .............................................................................................. 15
3 HRDLGetMinMaxAdcCounts ................................................................................................. 16
4 HRDLGetNumberOfEnabledChannels ................................................................................... 17
5 HRDLGetSingleValue ............................................................................................................ 18
6 HRDLGetSingleValueAsync ................................................................................................... 19
7 HRDLGetTimesAndValues .................................................................................................... 21
8 HRDLGetUnitInfo ................................................................................................................. 22
9 HRDLGetValues ................................................................................................................... 24
10 HRDLOpenUnit .................................................................................................................. 25
11 HRDLOpenUnitAsync ......................................................................................................... 26
12 HRDLOpenUnitProgress ..................................................................................................... 27
13 HRDLReady ........................................................................................................................ 28
14 HRDLRun ........................................................................................................................... 29
15 HRDLSetAnalogInChannel .................................................................................................. 30
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IIADC-20/ADC-24 User's Guide
16 HRDLSetDigitalIOChannel (ADC-24 only) ........................................................................... 31
17 HRDLSetInterval ................................................................................................................. 33
18 HRDLSetMains ................................................................................................................... 34
19 HRDLStop .......................................................................................................................... 35
5 Programming examples ..................................................................................................................... 36
6 Sequence of calls and data flow .......................................................................................................... 37
1 Streaming recording methods ................................................................................................ 37
2 Single-value recording methods .............................................................................................. 39
6 Glossary .................................................................................................................................... 40
7 Appendix A: Connecting the data logger in Windows XP ........................................................ 42
Index ........................................................................................................................................... 44
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

1 Introduction
1 Introduction
1.1 Overview
The ADC-20 and ADC-24 High-Resolution Data Loggers are multichannel, high-
accuracy USB data loggers for use with PCs. They require no external power supply
and take up no expansion slots. They come complete with PicoLog, a program offering
all the features of a stand-alone data logger.
You should have the following items in your ADC-20 or ADC-24 package:
ADC-20 or ADC-24 High-Resolution Data Logger
Pico Technology Software and Reference CD
Installation Guide
The CD includes driver software that enables you to write your own programs to
control the data logger, using a variety of popular programming languages.
The hardware and software are compatible with Microsoft Windows XP (SP3) or later.
Optional accessories
PP310 ADC-20/ADC-24 Terminal Board
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2ADC-20/ADC-24 User's Guide
2 Notices
2.1 Safety warning
We strongly recommend that you read the general safety information below before
using your product for the first time. If the equipment is not used in the manner
specified, then the protection provided may be impaired. This could result in damage
to your computer and/or injury to yourself or others.
Maximum input range. The ADC-20 and ADC-24 are designed to measure voltages
in the range ±2.5 volts, but are protected against overvoltages of ±30 volts. Any
voltages outside the overvoltage protection range may cause permanent damage to
the unit.
Mains (line) voltages. The ADC-20 and ADC-24 data loggers are not designed for
use with mains (line) voltages.
Safety grounding. The ground of every product is connected directly to the ground of
your computer via the interconnecting cable provided. This is done to minimize
interference. If the PC (especially laptops) is not grounded, reading stability cannot be
guaranteed and it may be necessary to manually ground the equipment.
As with most data loggers, you should take care to avoid connecting the inputs of the
product to any equipment which may be at an unsuitable voltage. If in doubt, use a
meter to check that there is no hazardous AC or DC voltage. Failure to check may
cause damage to the product and/or computer and could cause injury to yourself or
others.
You should assume that the product does not have a protective safety earth. Incorrect
configuration and/or use on voltages outside the maximum input range can be
hazardous.
Repairs. The unit contains no user-serviceable parts: repair or calibration of the unit
requires specialized test equipment and must be performed by Pico Technology
Limited or their authorized distributors.
2.2 Legal information
The material contained in this release is licensed, not sold. Pico Technology Limited
grants a license 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.
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

3 Notices
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
license is that it excludes usage in mission-critical applications, such as 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.
2.3 CE notice
The ADC-20 and ADC-24 meet the intent of EMC directive 89/336/EEC and meets
the EN61326-1 (1997) Class B Emissions and Immunity standard.
The ADC-20 and ADC-24 also meet the intent of the Low Voltage Directive and meet
the BS EN 61010-1:2001 IEC 61010-1:2001 (safety requirements for electrical
equipment, control, and laboratory use) standard.
A Declaration of Conformity is available from Pico Technology Ltd.
2.4 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.
A Declaration of Conformity is available from Pico Technology Ltd.
2.5 Trademarks
Pico Technology Limited and PicoLog are trademarks of Pico Technology Limited,
registered in the United Kingdom and other countries.
PicoLog and Pico Technology are registered in the U.S. Patent and Trademark
Office.
Windows and Excel are registered trademarks of Microsoft Corporation in the USA
and other countries.
2.6 Updates
We provide upgrades, free of charge, from our web site. We reserve the right to
charge for updates or replacements sent out on physical media.
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4ADC-20/ADC-24 User's Guide
2.7 Support and refunds
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 14
days of purchase for a full refund.
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

5 Getting started
3 Getting started
3.1 Installing the software
Before you connect the ADC-20 or ADC-24 to your computer for the first time, you
must install the software supplied on the CD. Insert the Software and Reference CD,
then follow the Install Software link.
A 32-bit driver is installed automatically along with the PicoLog software. Alternatively,
you can download the software development kit (SDK) from our website at
www.picotech.com: this is available with 32-bit or 64-bit drivers.
3.2 Connecting the data logger
You must install the software before plugging in the data logger. When you have
installed the software, connect the data logger's USB cable to a spare USB port on
your computer and wait until Windows displays the message "Device is ready to use".
3.3 Starting PicoLog
To check that the data logger is working, start the PicoLog application as follows:
1. Start PicoLog. (Click the PicoLog icon: in your Windows Start
menu).
2. Click File.
3. Point to New settings.
4. At the Recording dialog, click OK.
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6ADC-20/ADC-24 User's Guide
5. At the Sampling Rate dialog, click OK.
6. In the Converter details dialog, set the Converter type to High Resolution
Data Logger. The device type and serial number should appear in the USB
Devices list, and the USB enumeration progress indicator should gradually
move towards 100%. If the progress indicator does not start moving, disconnect
and reconnect the unit and then press Refresh.
7. Click OK.
8. At the ADC-20 (or ADC-24) channels dialog, double-click on "Channel 1".
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

7 Getting started
9. At the Edit ADC-20 (or ADC-24) Channel dialog, click OK.
10. Back at the ADC-20 (or ADC-24) Channels dialog, click OK.
11. The PLW Recorder view should now display the voltage on channel 1 (near 0 mV
if nothing connected).
12. Connect a suitable voltage (for example, from a 1.5 V battery) to the channel. Pin
connections are marked on the logger and also listed in the Analog connector
topic.
adc20.en r6 Copyright © 2005–2016 Pico Technology Ltd. All rights reserved.

i
8ADC-20/ADC-24 User's Guide
4 About the unit
4.1 Introduction
The ADC-20 and ADC-24 High-Resolution Data Loggers offer the ultimate in precise
and accurate readings. Features such as true differential inputs, galvanic isolation and
software-selectable sample rates all contribute to a superior noise-free resolution.
The ADC-20 is equipped with a 20-bit A/D converter, and can maintain a gain error of
0.2%. The four true differential inputs may be configured as eight single-ended inputs
or any combination in between, such as two differential and four single-ended. The
ADC-24 is equipped with a 24-bit A/D converter, and can maintain a gain error of
0.1%.
The eight true differential inputs may be configured as 16 single-ended inputs or any
combination in between. Power and connection to a PC or laptop is through a USB 1.1,
USB 2.0 or 3.0 port. Using the supplied PicoLog software, you can record, monitor and
analyze collected data, even exporting to third-party applications such as Microsoft
Excel.
4.2 Specifications
Common-mode range
Channel to common
Channel to common
Common to earth ground
Input channels
Differential
Single-ended
Conversion time per channel
Input voltage ranges
Resolution
Noise-free resolution
Overvoltage protection
±1.9 V (±39 mV to ±1250 mV ranges)
±3.0 V (±2500 mV range)
±30 V
ADC-20
ADC-24
Configurable up to 4
Configurable up to 8
Configurable up to 8
Configurable up to 16
60 ms, 100 ms, 180 ms, 340 ms, 660 ms
2 ranges
±1250 mV and ±2500 mV
7 ranges
±39 mV to ±2500 mV
20 bits
24 bits
See table below
±30 V between any input and common
Common-mode rejection
ratio
Channel to common
Common to earth ground
Noise rejection
Input impedance
Gain error from source
mpedance
Gain error
95 dB (DC to 60 Hz)
>125 dB (DC to 60 Hz)
120 dB typical at 50 to 60 Hz
2 MΩ (differential), 1 MΩ (single-ended)
0.5 ppm per ohm source impedance
due to input impedance
0.2%
0.1%
(0.2% at ±2500 mV)
Offset error
36 µV (±1250 mV range)
400 µV (±2500 mV range)
6 µV (±39 mV range)
7 µV (±78 mV range)
9 µV (±156 mV range)
13 µV (±313 mV range)
20 µV (±625 mV range)
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

i
9 About the unit
ADC-20
ADC-24
Digital I/O
Output level, high
Output level, low
Input level, high
Input level, low
Isolation (input to input)
Isolation (input to ground)
Reference output
Power outputs
Environmental conditions
Operating temperature
None
4
> 2.40 V
< 0.40 V
> 2.20 V
< 0.88 V
None
Galvanic, up to ±30 V
AGND and DGND isolated
+2.5 V ±2.5 mV @ 2 mA
+5 V ±1.0 V @ 2 mA
-5 V ±1.5 V @ 2 mA
0 ºC to 45 ºC
PC connection
Quoted input accuracy
Storage temperature
Operating humidity
Storage humidity
Recommended calibration
nterval
USB 1.1 (USB 2.0 compatible)
Cable length approx. 4.4 m (13.8 ft)
20 ºC to 30 ºC
-20 ºC to 60 ºC
5% to 80% RH, non-condensing
5% to 95% RH, non-condensing
1 year
Input connector
DB25 female
Power supply
100 mA (max.) from USB port
13.5 cm x 18.4 cm x 3.6 cm
Dimensions
(5.31 in x 7.24 in x 1.41 in)
Weight
Approx. 505 g (17.8 oz)
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10ADC-20/ADC-24 User's Guide
4.3 Analog connector
Analog inputs are connected to the ADC-20 and ADC-24 through the female DB25
connector. The connections are as follows:
Pin
Function
Pin
Function
1
Channel 2 (Channel 1-)
14
Channel 1
2
Channel 4 (Channel 3-)
15
Channel 3
3
Channel 6 (Channel 5-)
16
Channel 5
4
Channel 8 (Channel 7-)
17
Channel 7
5
Channel 10 (Channel 9-)
18
Channel 9
6
Channel 12 (Channel 11-)
19
Channel 11
7
Channel 14 (Channel 13-)
20
Channel 13
8
Channel 16 (Channel 15-)
21
Channel 15
9
Analog Ground
22
Digital Ground
10
+5 volts
23
Digital I/O 1
11
-5 volts
24
Digital I/O 2
12
+2.5 volts
25
Digital I/O 3
13
Digital I/O 4
Note 1: Channel numbers in brackets apply when the input is set to differential
mode.
Note 2: Channels 9 to 16 exist only on the ADC-24.
Note 3: Digital I/Os 1 to 4 exist only on the ADC-24.
Note 4: Pins 10 and 11 are low-current outputs for powering small sensors. Do
not exceed the current limits given in the Specifications table.
Note 5: The analog and digital grounds are not connected together inside the
unit. You should not connect them together externally, as this would
degrade the accuracy of the unit.
Note 6: For easy connection to the DB25 connector, we recommend that you use
the ADC-20/ADC-24 terminal board.
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11 About the unit
4.4 Noise-free resolution and conversion time
The table below shows the number of noise-free bits of resolution for the full range of
conversion times.
Conversion Voltage range
time & Noise-free resolution (bits)
per
channel ±39 mV ±78 mV ±156 mV ±313 mV ±625 mV ±1250 mV ±2500 mV
ADC-24 only ADC-20 and ADC-24
660 ms 17 18 19 20 20 20 20
340 ms 17 18 19 19 19 20 20
180 ms 16 17 18 19 19 19 19
100 ms 16 17 18 18 18 19 19
60 ms 15 16 17 18 18 18 18
4.5 ADC-20/ADC-24 terminal board
For easy connection to the DB25 connector, we recommend that you use the ADC-20/
ADC-24 terminal board, part number PP310. This has screw terminals to allow you
to connect wires to all of the data logger's inputs and outputs without soldering. It also
has space for voltage-divider resistors, a temperature sensor and a quad op-amp.
See the ADC-20/ADC-24 Terminal Board User's Guide for instructions on connecting
signals to the terminal board. If you are not using a terminal board, you can still refer
to the Terminal Board User's Guide for information on connecting various types of
signal to the data logger. http://www.elso.sk/product.php?id_product=2136
4.6 LED
The ADC-20 and ADC-24 have an LED, next to the entry point of the USB cable, that
you can use to verify that the unit is working. The LED flashes whenever the unit is
taking readings. It also flashes briefly during "enumeration", the process that PicoLog
uses to detect all Pico USB devices plugged in to the computer.
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12ADC-20/ADC-24 User's Guide
5 Programmer's reference
5.1 Recording methods
The ADC-20/ADC-24 driver provides three methods of recording data. All these
methods support USB 1.1.
Streaming
The driver constantly polls the device, and samples are placed in a buffer until
retrieved by your application. Precise sample timing is controlled by the unit.
Single Value (blocking)
You make a single request for a sample, blocking the calling thread, and when the
sample has been received the driver returns the value to your application.
Single Value (non-blocking)
You make a single request for a sample without blocking the calling thread, and
when the sample has been received the driver returns the value to your
application.
5.2 Windows driver
The picohrdl.dll dynamic link library (DLL) in the lib subdirectory of your SDK
installation is a driver that allows you to program your ADC-20 or ADC-24 data logger.
It is supplied in 32-bit and 64-bit versions. The driver exports the function definitions
in standard C format, but this does not limit you to programming in C. You can use the
API with any programming language that supports standard C calls. It can also be
used with programs like Microsoft Excel. The driver supports all Windows operating
systems from Windows 7 onwards.
5.3 Scaling
To convert from ADC values to volts, first obtain the minimum and maximum ADC
values for the selected channel by calling the HRDLGetMinMaxAdcCounts function in
the driver. Next, scale the ADC value to the voltage range you specified when you
called HRDLSetAnalogInChannel. You can calculate the voltage range
programmatically by using
Vmax = 2500 mV / (2^r)
where r is the range constant you supplied to HRDLSetAnalogInChannel (0 for
±2500 mV, 1 for ±1250 mV and so on).
You can then use Vmax to calculate the scaled voltage, V, with the following formula
V = (raw_ADC_value / max_ADC_Value) * Vmax
where raw_ADC_value is the reading from the device and max_ADC_value is the max
ADC value for the device obtained from HRDLGetMinMaxAdcCounts.
Copyright © 2005–2016 Pico Technology Ltd. All rights reserved. adc20.en r6

13 Programmer's reference
5.4 Driver functions
The following sections describe the functions available to an application using the
ADC-20 and ADC-24. All functions are C functions using the standard call naming
convention (__stdcall) and are exported with both decorated and undecorated
names.
Function
Description
HRDLCloseUnit
Shuts down unit
HRDLCollectSingleValueAsync
Starts the unit sampling one value without
blocking the calling application's flow
HRDLGetMinMaxAdcCounts
Returns the maximum and minimum ADC count
available for the device
HRDLGetNumberOfEnabledChannels
Returns the number of analog channels enabled
HRDLGetSingleValue
Takes one sample for the specified channel at
the selected voltage range and conversion time
HRDLGetSingleValueAsync
Retrieves the reading when the
HRDLCollectSingleValueAsync has been called
HRDLGetTimesAndValues
Returns the requested number of time-stamped
samples for each enabled channel
HRDLGetUnitInfo
Writes unit information to a character string
HRDLGetValues
Returns the requested number of samples for
each enabled channel
HRDLOpenUnit
Opens data logger unit
HRDLOpenUnitAsync
Opens unit without blocking the calling thread
HRDLOpenUnitProgress
Checks the progress of an asynchronous open
operation
HRDLReady
Indicates when readings are ready to be
collected
HRDLRun
Starts the device sampling and storing the
samples into the driver's buffer
HRDLSetAnalogInChannel
Enables or disables the analog channel
HRDLSetDigitalIOChannel
Sets a digital output or input (ADC-24 only)
HRDLSetInterval
Sets the sampling time interval
HRDLSetMains
Sets the mains noise rejection frequency
HRDLStop
Stops the device when streaming
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14ADC-20/ADC-24 User's Guide
5.4.1 HRDLCloseUnit
int16_t HRDLCloseUnit
( int16_t handle
)
Shuts down a data logger unit.
Arguments
handle
The handle, returned by HRDLOpenUnit, of the unit being closed
Returns
1 if a valid handle is passed
0 if not
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15 Programmer's reference
5.4.2 HRDLCollectSingleValueAsync
int16_t HRDLCollectSingleValueAsync
( int16_t handle,
int16_t channel,
int16_t range,
int16_t conversionTime,
int16_t singleEnded
)
This function starts the unit sampling one value without blocking the calling
application's flow. Used in conjunction with HRDLGetSingleValueAsync and
HRDLReady.
Arguments
handle
Handle returned by HRDLOpenUnit
channel
Channel number to convert. If the channel is not valid then the
function will fail.
range
The voltage range to be used. If the range is not valid, the
function HRDLGetSingleValueAsync will return 0.
conversionTime
The time interval in which the sample should be converted. If the
conversion time is invalid,the function HRDLGetSingleValueAsync
will fail and return 0.
singleEnded
The type of voltage to be measured:
0: differential
nonzero: single-ended
Returns
1 if a valid handle is passed and the settings are correct
0 if not
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16ADC-20/ADC-24 User's Guide
5.4.3 HRDLGetMinMaxAdcCounts
int16_t HRDLGetMinMaxAdcCounts
( int16_t handle,
int32_t * minAdc,
int32_t * maxAdc,
int16_t channel
)
This function returns the maximum and minimum ADC count available for the device
referenced by handle.
Arguments
handle
Handle returned by HRDLOpenUnit
minAdc
Pointer to an int32_t, used to return the minimum ADC count
available for the unit referred to by handle
maxAdc
Pointer to an int32_t, used to return the maximum ADC count
available for the unit referred to by handle
channel
Channel number for which maximum and minimum ADC count are
required
Returns
1 if a valid handle is passed
0 if not
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17 Programmer's reference
5.4.4 HRDLGetNumberOfEnabledChannels
int16_t HRDLGetNumberOfEnabledChannels
( int16_t handle,
int16_t * nEnabledChannels
)
This function returns the number of analog channels enabled.
Arguments
handle
Handle returned by HRDLOpenUnit
nEnabledChannels
Pointer to an int16_t, where the number of channels enabled
will be written
Returns
1 if a valid handle is passed
0 if not
adc20.en r6 Copyright © 2005–2016 Pico Technology Ltd. All rights reserved.