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Keithley’s 2460 Sourcemeter Review by Jim Rowe The Keithley 2460 SMU (Source Measure Unit) is a programmable 100W DC power source and load combined with a 6.5-digit DMM. Most of its functions can be controlled via its large touch screen or from a PC via its USB input. As well as functioning as a DC power supply, it can be used to plot a wide range of parameters for high power semiconductor devices. S o what exactly is an SMU and what’s it used for? Well, what would you need for measuring the I/V (current/voltage) characteristics of a wide range of semiconductor devices – like diodes, bipolar transistors and Mosfets? First, you’d need at least one accurately adjustable DC power supply or ‘source’, plus one or more accurate DMMs (digital multimeters) to measure the device current and voltage. You would also need a program78  Silicon Chip mable electronic load. Combine all that and you would have something like the Keithley 2460. Not only does it have a digitally programmable DC source, a programmable electronic load and a 6.5-digit DMM, there’s also a microcontroller capable of running multi-level ‘sweep’ scripts to measure the current drawn by the DUT (device under test) at a series of programmable voltage levels, and then displaying the results in either tabular form or as an I/V graphical plot. It could also be used for applications like cycling of rechargeable batteries and characterisation of electrochemical deposition, corrosion and electroplating. Most of the test parameters and settings are made via its 127mm (diagonal) touch-screen colour LCD, using a series of menu screens. The touch-screen incorporates ‘swipe’, ‘pinch’ and ‘zoom’ functions, for intuitive manipulation of the on-screen siliconchip.com.au A closeup of the rear of the Keithley 2460, showing the range of comms I/O connectors along the bottom and the power input at upper right. The orange terminal strip in the centre provides the alternative ‘rear’ test connections. displays (just like on a smart-phone). Capabilities The programmable source and load can together provide full fourquadrant measurements, with a maximum source voltage of ±105V and a maximum current level of ±7A (DC or pulse). Maximum voltage and current are not available at the same time; the maximum power rating is 100W. The 6.5-digit DMM offers a basic accuracy of 0.012%, six voltage measuring ranges covering 200.0000mV to 100.0000V full scale, with resolutions ranging from 100nV to 100µV, and 10 current measuring ranges covering from 1.000000µA to 7.000000A full scale, with resolutions ranging from 1pA to 1µA. There are eight resistance measurement ranges, with either local or remote sensing, 2-wire or 4-wire measurement and full scale readings ranging from 2.000000Ω (resolution 1µΩ) to 20.0000MΩ (resolution 10Ω), plus a ninth range for values over 20MΩ using a user-defined test current. As well as offering a wide choice of source and measurement setting options, the 2460’s micro has an in-built Test Script Processor (TSP) function which allows it to run built-in scripts for multi-level ‘sweeps’ and I/V curve plotting. It also offers four ‘Quickset’ options to enable one-touch set-ups for basic measurement jobs like a voltmeter, an ammeter, an ohmmeter and an accurately programmable power supply. Other neat features offered by the 2460 in ‘local’ (ie, free-standing) mode include the ability to select either continuous or single-shot testing with manual triggering via a button on the front panel, the ability to choose between test connectors on either the front or rear panels, a built-in contextsensitive help facility, the ability to choose either manual or automatic measurement ranges and also the ability to select Linear, Log, Dual Linear, Dual Log and Custom sweeps. There’s also a USB 2.0 port on the front panel for saving test scripts as well as test results to external USB memory. The connection options on the rear panel comprise an RJ-45 Ethernet connector, a USB type B socket, a female DB-9 connector for Here’s the 2460’s built-in main Menu screen, used for selecting just about all of its configuration, testing and display functions via the touch-screen facility. It even provides ‘swipe’, ‘pinch’ and ‘zoom’ functions, like a smartphone. siliconchip.com.au February 2016  79 a shunt’s resistance value as a function of current – right up to current levels of 7A. That’s not something you can easily do with the 7562 alone, or with any standard DMM for that matter. I also tried setting the Power Supply section of the 2460 to various reference DC voltages and checking its output with my trusty Yokogawa. The results were again very impressive, with the readings on the 7562 within 15 ppm of the voltage settings on the 2460. For example, a setting of ‘10.0000V’ gave a reading of ‘10.00008 V’, while a setting of ‘2.04800V’ gave a reading of ‘2.04802 V’. After this I tried using the 2460’s built-in ‘Sweep’ script to check the voltage-current charThis is the other main screen displayed by the 2460 – the Home screen, used to set up, configure and numerically display the test parameters. It too makes full use of the acteristic of various 2-terminal touch-screen facility, to make testing fast and intuitive. semiconductor devices, like a forward-biased LED, a standard direct digital connections, a pair of Configuration Panel, which is used to 1A silicon diode and then a Schottky TSP-Link connectors for linking into install and set up the various drivers diode. Then I progressed to checking the reverse-biased characteristic of a a multi-instrument test system and an needed to link the 2460 to the PC. IEEE-488 connector for GPIB interconPart of the Configuration Panel soft- 3.9V zener diode, in each case using nection. ware appears to be a subset of National the 2460’s ‘Graph’ mode to plot the Most users will probably want to Instruments’ NI-VISA 5.3 Runtime, E/I curve directly on its screen (see the screen shots in Figs.1&2 below). link up the 2460 to their laptop via which gets installed along with it. Then it was time to try linking it up either USB or Ethernet, and with this to my Asus P550L i7 laptop PC, runin mind it comes with cables for either. What we found To make it possible for users to start Initially and in order to become ning Windows 7 Pro (64-bit). So folmaking measurements with the 2460 familiar with the 2460 and its touch- lowing the instructions in Keithley’s as quickly as possible, it comes with a screen menu, I tried performing quick KickStart Software Quick Start Guide, CD-ROM providing both ‘Quick Start’ ‘manual’ tests like 4-wire measure- I started installing the necessary softand ‘Reference’ user manuals in PDF ments on low-value resistors and ware and drivers for a USB connection form, plus a free instrument control/ current shunts of known value. Here between the two. This turned out to be quite a rigstartup software package called Kick- the results compared very closely with Start. the readings from my Yokogawa 7562 marole and along the way you find The latter incorporates the KickStart 6.5-digit DMM. However due to the yourself asked to verify your agreecontrol application and a comms extra capabilities of the 2460 I was ment with various software copyright configuration manager called Keithley also able to measure the variation in licences – not just with Keithley, but Fig.1: The E-I plot of a red LED, as displayed directly on the 2460’s screen by selecting the ‘Graph’ tab at the top. 80  Silicon Chip Fig.2: Again displayed directly on the 2460’s screen this shows the reverse bias E-I plot for a 3.9V zener diode. siliconchip.com.au also with National Instruments and another crowd called IVI Foundation Inc. And some of the software components seem to need you to set various options, some of which are not covered in the Quick Start Guide; not straightforward, at all! When I thought I had installed all the software, plugged in the USB cable from the 2460 and then tried firing up the KickStart software to see if they could ‘talk’ to each other, they couldn’t. KickStart couldn’t find the instrument at all and showed only its built-in ‘virtual instrument simulations’. Confusingly, when I went into Windows’ Control Panel and then Device Manager, it was showing the 2460 as a USB Test and Meas- Fig.3: the KickStart software screen when showing the results of the zener diode E-I urement Device (IVI) and said it test, performed again remotely via the USB interface. Note the less than ideal graph legend visibility, due to the mid-grey background. Currently you have to export the was ‘working properly’. This was promising, and when I graph as a PNG file and print it out to get full visibility. also fired up Keithley’s Configuration Panel it too showed the 2460 as As you can see from the screen grab uring flexibility way beyond that of hooked up and operating correctly. So of Fig.3, the graph window background standard DMMs, the Keithley 2460 why wasn’t KickStart able to find it? seems to be fixed at a mid-grey, with SMU is a surprisingly easy instrument Hmmm – perhaps my copy of Kick- the axis lines and legends in black. to ‘drive’ – whether you are using it Start was somehow corrupted. So I Although you can change the colour alone or hooked up to a PC running tried going to the Keithley/Tektronix of the graph plot itself for maximum the KickStart software. website and downloading a fresh copy visibility, this still makes it a bit difIt would therefore make a good of the latest version. Then it was a mat- ficult to read the legends. choice for anyone who needs to do ter of uninstalling the original copy of The only way to get a really clear a lot of characteristic curve plotting. KickStart, extracting everything from image of a graph seems to be to export the new download and installing it it as a PNG image file, then import it Where do you get it? all over again. into an image editor like Photoshop or Australian readers should contact This time I also tried to stay focussed Paint.net and either view it on screen Vicom at their Melbourne office, phone on the various options which needed or print it out like the graph shown in (03) 9575 0111, or via their website: to be selected during the installation Fig.4 (below). www.vicom.com.au/page/173/vicom– particularly those for the NI-VISA By the way KickStart also allows --smus or email: info<at>vicom.com.au Runtime drivers. In fact I made sure you to export test results in tabular New Zealand readers can contact that ALL of the drivers were selected form, in either Excel or CSV (comma the Auckland office on (09) 3794596, for installation this time, even those separated variable) formats. or via the NZ website www.vicom. that didn’t seem to be appropriate So the bottom line is that as well co.nz/page/173/vicom---smus or email: SC when I was only preparing for USB as having high accuracy plus meas- info<at>vicom.co.nz communication. Finally, this time KickStart was able to ‘find’ the 2460 SMU and I was able to try using the laptop to control the 2460 as a complete ‘testing system’. Now setting up and running tests and characteristic plots for various devices proved to be even easier and more intuitive than with the 2460 by itself. Mind you, my laptop doesn’t have a touch-screen, so I had to do all of the on-screen setting up using the mouse... Perhaps my only real criticism of KickStart is that it doesn’t seem to offer Fig.4: this printout of the above screen shows the rather dramatic difference in much in the way of options regarding legibility over the on-screen view above (Fig.3). It’s a shame that there is no way on-screen graph visibility. to adjust screen contrast, etc, to achieve a much clearer result. siliconchip.com.au February 2016  81