Since I last talked about data acquisition and data logging
via the PC’s USB port, there have been a number of interesting
product developments. Of course, they are too numerous to list
in this report but here are some of my favourites, just to give
you a taste of the possibilities.
Lascar Electronics (www.lascarelectronics.com)
has added the EL-USB-3 to its popular EL-USB range of stand alone
data loggers - and at a one-off price of £39 it has to be
a bargain. The unit has a measurement range of 0-30V, which covers
the outputs of a variety of sensor types. You just connect it to
the USB port, configure the sampling rate, set the alarms, etc,
remove it from the PC and connect to the measured voltage via integral
screw terminals. Up to 32,000 readings can be stored and these
can be downloaded on re-connection to the PC.
Keithley Instruments’ (www.keithley.com)
new KUSB-3100 series modules offer a great alternative to ISA,
PCI and PCMCIA data acquisition cards, which can be a hassle to
connect to the PC motherboard, not to mention their time-consuming
set-up procedure. These modules support USB fullspeed data rates;
the top-of the range KUSB- 3116, for example, is USB 2.0 compliant,
providing functionality at the USB high-speed 480 Mbit/s data transfer
rate. This increased bandwidth lets users perform multiple I/O
operations simultaneously at throughput rates up to 500kHz in each
direction - similar to PCI.
The DLP-TH1 USB based temperature and humidity sensor from Audon
Electronics (www.audon.co.uk) is supplied with Windows compatible
software that displays temperature, humidity and dew point in both
Celsius and Fahrenheit, plots graphically to screen and logs to
a data file on the hard disk. The software will even send an email
to specified recipients when readings exceed predetermined limits.
Audon’s customers can freely download the most recent versions
of the software, together with the USB drivers, from www.dlpdesign.com/usb/th1.html.
So long as their consumption is low enough, you can power devices
through the USB port; moreover, you can mount your USB data logger
at distances of up to 5m from the computer. These advantages are
put to effective use in Omega’s (www.omega.com) OMB-DAQ 54/55/56
series multi-function data acquisition modules, which offer 22-bit
resolution, ten single-ended (five differential) analogue input
channels and built-in cold junction compensation for direct thermocouple
measurements. Up to 100 OMBDAQ modules can be attached to one PC
via USB hubs to provide a total of 8,000 channels, but of course
a separate power supply is required for this configuration.
Temperature
monitoring is the key function of Measurement Computing’s
(http://mcc.adeptscience.co.uk) new USB-TEMP module. Offering an
unusually flexible capability for its price (£355), this
board provides eight temperature inputs, each supporting all of
the common thermocouple types, two-, three- or four-wire RTDs and
thermistors. The unit comes complete with Windows compatible software,
including the TracerDAQ strip-chart recorder and data logger application
and SoftWIRE, a graphical programming interface for Visual Studio.Net.
Drivers are also available for most popular data acquisition packages,
including National Instruments’ (NI’s) LabVIEW.
Of course,
NI (www.ni.com/usb) also offers a huge portfolio of data acquisition
hardware. Its latest USB 2.0 compatible product is the USB-9000
series, comprising eight models that offer either four or eight
channels and a variety of resolutions and sampling speeds. The
USB 9211A, for example is a four-channel, 24-bit thermocouple input
module, while the USB 9221 is an eightchannel, 12-bit, high voltage
analogue input unit that has a very fast sampling rate of 800kS/s.
Grant
Instruments (www.grant.co.uk) continues to develop its Squirrel
range of data loggers. The latest model, the SQ2040-4F16, is a
16-channel unit with four independent A/D converters and twin processors.
It will measure and log data from a variety of sensor types at
up to 100 readings per second, simultaneously on separate channels,
which Grant believes is a first for this class of product. The
logger has a 16Mbyte memory that allows direct storage of up to
two million readings. Both USB and RS232 communications are offered,
along with Ethernet and GSM wireless.
And while on the subject
of RS232, if your existing data loggers are based on this serial
communications protocol, you can still connect them to the USB
port using a USB -to- RS232 converter. These devices connect to
the host computer USB port via a standard USB cable and provide
a DB25 or DB9 serial port for use with RS232 devices. Ontrak Control
Systems (www.ontrak.com), among others, can offer help in this
area.
Dr Know's recommended download is USB-TEMP - Specifications - download yours today.