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By JIM ROWE Precision 10V DC reference for checking DMMs Have you ever checked the calibration of your digital multimeter? Yeah, we know – you haven’t because there is no easy (read cheap) way of doing it. But now you can with this precision DC voltage reference that can be built in a few hours. Without any need for adjustment it will provide you with a 10.000V DC source accurate to within ±3mV, ie, an accuracy of ±0.03%. M OST OF US DON’T ever get our DMMs calibrated, though they do drift out of calibration over years of use. If you are using them in your occupation, they should be checked every year or so – otherwise how can you trust the readings? But it can cost quite a bit to send a DMM away to a standards lab for calibration – more than many DMMs are worth. So generally we either hope for the best or simply buy a new DMM if we suspect that our existing meter has drifted too far out of calibration. Back in the 1970s when DMMs first became available, the only practical 62  Silicon Chip source of an accurately known DC voltage was the Weston cell, a wet chemical “primary cell” which had been developed in 1893 and had become the international standard for EMF/ voltage in 1911 (see panel). It produced an accurate 1.0183V reference which could be used to calibrate DMMs and other instruments. Unfortunately, Weston cells were fairly expensive and few people had direct access to one for meter calibration. As a result, most people tended to use a reasonably fresh mercury cell as a “poor man’s” voltage reference. Fresh mercury cells have a terminal voltage very close to 1.3566V at 20°C and this falls quite slowly to about 1.3524V after a year or so. Silver oxide cells can also used for the same purpose, having a stable terminal voltage very close to 1.55V. Of course, batteries of any kind have a tendency to obey Murphy’s Law and usually turn out to have quietly expired before you need them. And although mercury and silver oxide cells have quite a long life, especially if you use them purely as a voltage reference, they certainly aren’t immune to this problem. Which means that these batteries make a pretty flaky siliconchip.com.au voltage reference, at best. Fortunately, in the 1980s semiconductor makers developed a relatively low-cost source of stable and accurately predictable DC voltage: the precision monolithic voltage reference (PMVR). This is a kind of up-market relative of the familiar 3-terminal voltage regulator IC. Like 3-terminal regulators, PMVRs produce a regulated DC output voltage when they are fed with unregulated DC power. The Analog Devices AD588 device we’re using in this new voltage reference project incorporates a number of recent advances in PMVR technology. These include an ion-implanted “buried” zener reference diode plus high-stability thin-film resistors on the wafer, which are laser trimmed to minimise drift and provide high initial accuracy. It also incorporates highly stable on-chip op amps which are configured to allow Kelvin connections to the load and/or external current boosters, for driving long lines or high current loads. Block diagram You can see what’s inside the AD588 in the block diagram of Fig.1. The voltage reference cell is at upper left, consisting of the “buried” zener (6.5V) and its current source together with op amp A1. All the resistors (R1-R6) are high-stability thin-film resistors, laser trimmed to allow the gain of A1 to be set to a high degree of precision – so the cell’s basic output voltage (between pins VHI and VLO) is initially set to 10.000V ±3mV (for the AD588JQ/AQ version we use here), without any external adjustment. Temperature compensation inside the cell also gives the basic voltage reference a very low temperature drift coefficient: typically ±2ppm/°C. In addition, resistors R4 and R5 can be configured to provide a very accurate “centre tap” for this voltage, allowing the chip to be used as a precise source of ±5.000V ±1.5mV. Although this basic untrimmed initial accuracy of the AD588 (10.000V ±0.03%) is quite good enough for calibrating the majority of low-cost DMMs, the chip can also be trimmed very easily to improve its accuracy by a factor of greater than 10 times – ie, to an accuracy around ±0.002%. This is done by connecting the GAIN ADJ pin to a 100kΩ trimpot, connected siliconchip.com.au VHI +Vs (2) A3 IN (6) (4) NOISE REDUCTION (3) A3 SENSE (7) RB A3 6.5V GAIN ADJ (5) A1 R3 (1) A3 OUT R1 R4 R2 R5 A4 GND SENSE+ R6 (9) (15) A4 OUT (14) A4 A2 SENSE GND (10) SENSE– (16) –Vs (8) VLO (12) BAL ADJ (11) VCT (13) A4 IN Fig.1: block diagram of the AD588 voltage reference. It contains four op amps (A1-A4) plus a “buried” zener and its current source to provide the voltage reference cell. Specifications Output voltage: 10.000V DC Sensing: internal or remote sensing to compensate for output cable voltage drop Basic accuracy: ±0.03% (±3mV) without adjustment, ±0.002% after optional trim adjustment and calibration Long term drift: <15ppm per 1000 hours, mostly in first year of operation Temperature coefficient: 3ppm/°C between -25°C and +85°C Maximum output current: 10mA Noise on output: less than 6mV RMS Load regulation: less than ±50μV/mA for loads up to 10mA Supply line regulation: less than 200μV/V Power supply: 12V AC, current drain <60mA between the VHI and VLO terminals. The pot allows the gain of A1 to be adjusted for a very small output voltage range (approximately -3.5mV to +7.5mV) without any adverse effect on temperature stability. Of course, in order to take advantage of this trimming feature, you must have access to an even higher precision voltage reference, to compare it with. Op amp A2 is used to allow accurate “ground sensing”, ensuring that the external system ground is accurately held at the same potential as VLO. And op amps A3 and A4, which are internally compensated, are provided to act as output buffers for the VHI and VLO voltages, as well as providing for a full Kelvin (ie, remote sensing) output connection. The full circuit As you can see from the circuit schematic of Fig.2, there’s not a great deal in our new precision voltage reference apart from the all-important AD588 chip (IC1). This does just about everything. All that we need to do in the rest of the circuit is provide it with a moderately regulated and filtered power source of ±15V and also make its buffered output voltage available, either at the main local terminals or at May 2009  63 68 +15V A 2200 F 25V K K ZD1 15V 1W A3 OUT A3 IN– D1 1.8k 11 A 12V AC INPUT 2 +Vs 470 F 100nF 16V A 22 12 BAL POWER  LED1 ADJ K 7 CON1 K A3 IN+ VHI IC1 AD588AQ (OR JQ) VLO A4 IN+ 9 A GAIN ADJ GND SENSE– NR 680nF MKT 1.8k D2 VCT A4 IN– GND SENSE+ A4 OUT 1 +10.00V OUT 3 S1a 4 6 TRIM VR1* 100k 25T 5 10 +10.00V SENSE INT/EXT SENSING 8 0V SENSE 13 14 S1b 15 0V OUT –Vs 68 –15V A 2200 F 25V K ZD2 15V 1W 470 F 100nF 16V 16 * TRIMPOT OPTIONAL (SEE TEXT) D1, D2: 1N4004 A SC  2009 PRECISION DC VOLTAGE REFERENCE ZD1, ZD2 A LED K K K A Fig.2: the circuit uses the AD588 precision voltage reference (IC1) and not much else. Diodes D1 & D2 function as halfwave rectifiers and feed zener diodes ZD1 & ZD2 to provide ±15V rails for the IC. the end of a cable connecting a remote load to them. The power supply configuration is quite straightforward and uses a halfwave rectifier circuit to produce each DC supply rail from a 12V AC input (which can be a 12V 500mA AC plugpack). Diodes D1 & D2 form the rectifiers, with filtering provided by two 2200μF electrolytic capacitors. Zener diodes ZD1 and ZD2 (both 15V types) then provide moderate regulation for the two supply rails, in conjunction with the two 68Ω series resistors. A small amount of additional filtering is provided by two 470μF electrolytics, together with 100nF bypass capacitors at the supply pins for IC1. Note that power indicator LED1 is connected directly between the two supply rails, in series with two 1.8kΩ current-limiting resistors. What This Voltage Reference Cannot Do While this 10V DC reference is very handy if you want to check the DC accuracy of your digital multimeter, it cannot tell you anything about your DMM’s accuracy in its other modes such as DC and AC current, AC voltage and resistance. So just because you have done a simple check on the DC voltage accuracy, don’t let it lull you into a false sense of security that everything is well with your DMM. In fact, it is possible that this 10V DC reference may alert you to the fact that your DMM has drifted well away from its initial calibration which may have been pretty good when you purchased it. How many years ago was that? 64  Silicon Chip If you are using DMMs in your occupation, they should be calibrated every year or so, otherwise you cannot really trust the readings. Moreover, if you have dropped your multimeter, it definitely should be suspected, particularly if its internal calibration is performed by tweaking potentiometers. Let’s face it, most DMMs get dropped from to time – that’s just normal. If you need a full performance verification of all functions and ranges for your work then that is best performed by an accredited calibration laboratory. For information and a quote on DMM calibration, contact Trio-Smartcal on 1300 134 091. www.triosmartcal.com.au The connections for IC1 itself are fairly easy to follow. The 680nF capacitor connected to ground from the NR pin (7) is included to provide additional low-pass filtering of any noise generated by the AD588’s buried zener. It works in conjunction with series resistor RB, as shown in Fig.1. Op amp A3 inside IC1 is used as the positive voltage output buffer, with its non-inverting input (pin 4) connected directly to VHI (pin 6). The inverting input (pin 3) is brought out to the external positive sense terminal (for remote sensing) and also to S1a, which allows it to be connected directly to the positive output (pin 1) for local sensing. Op amp A4 is connected in the same way, as the negative output voltage buffer. Here, the op amp’s non-inverting input (pin 13) is connected directly to the reference cell’s VLO output (pin 8), while the inverting input (pin 14) is brought out to the negative sense terminal for remote sensing and also to S1b, to connect it directly to the negative output (pin 15) for local sensing. So what is the purpose of the “optional” trimpot VR1? That is for trimming the AD588’s output voltage siliconchip.com.au 15V + FER V CD V51+ +10V OUT 100k IC1 AD588 TRIM INT/EXT SENSING 680nF V 5 115V 68 2200F 25V S1 + ZD2 470 F 100nF D2 4004 D1 4004 LED1 PWR 1.8k 1 diecast aluminium box, 111 x 60 x 54mm (Jaycar HB-5063 or similar) 1 PC board, code 04305091, 84 x 53.5mm 1 DPDT on-on mini toggle switch (S1) 1 2.5mm PC-mount DC power socket (CON1) 1 16-pin machined IC socket 2 binding post terminals, red 2 binding post terminals, black 4 M3 x 25mm tapped metal spacers 4 M3 x 6mm screws, countersink head 4 M3 x 6mm screws, pan head 1 100kΩ 25T top adjust trimpot (optional – see text) 1 150mm length blue hookup wire 1 150mm length red hookup wire 1 100mm length 0.7mm tinned copper wire N OI SI C E R P VR1 1.8k Parts List +10V SENSE 470 F 100nF 25V 22 CON1 12V AC INPUT 1 92200 0 5 0 3 40F 9002 © 68 ZD1 0V OUT 0V SENSE Fig.3: follow this diagram to install the parts on the PC board and complete the external wiring. Note that switch S1 actually mounts on the lid of the case and not directly on the PC board – see text. This view shows the completed PC board with the optional trimpot (VR1) in position. Install VR1 only if you intend calibrating the unit against a high-precision 10V reference. to higher precision than its “out of the box” ±3mV rating. We have made provision for the trimpot to be added to the PC board for this purpose but there is no point in fitting the trimpot unless you have access to a very high precision 10V reference. AD588 availability That’s about it regarding circuit operation. However, before we move on to discuss the project’s construction, a quick word about versions of the AD588 chip and its availability. Analog Devices apparently make five different versions of the AD588, one in a small outline (SOIC-W) SMD package and the others in 16-pin ceramic DIL packages. The four CERDIP devices have different initial error, Semiconductors 1 AD588AQ or AD588JQ voltage reference (IC1) – available from Futurlec (see text) 2 15V 1W zener diode (ZD1,ZD2) 1 5mm green LED (LED1) 2 1N4004 1A diodes (D1,D2) Capacitors 2 2200μF 25V RB electrolytic 2 470μF 16V RB electrolytic 1 680nF MKT metallised polyester 2 100nF MKT metallised polyester temperature range and temperature coefficient values. They range from the AD588BQ with 1mV of initial error, a -25°C to +85°C range and 1.5ppm/°C tempco down to the AD588JQ with 3mV of initial error, 0-70°C range and 3ppm/°C tempco. The AD588BQ is the most expensive (as you would expect), while the AD588JQ is the least expensive. None of the versions of the AD588 seems to be readily available in Australia, especially in one-off quantities. However, we were able to find one supplier who was able to supply the midrange AD588AQ version (3mV max initial error, -25°C to +85°C range and 3ppm/°C tempco) for A$28.50 each (at the time of writing) plus postage. The supplier concerned is Futurlec, which Resistors (0.25W 1%) 2 1.8kΩ 1 22Ω 2 68Ω is based in Broadmeadow NSW but does all of its business via the web. So Futurlec is our recommended source for the AD588AQ. You can order this part via their website at www.futurlec.com (item number AD588JN). Table 1: Resistor Colour Codes o o o o siliconchip.com.au No.   2   2   1 Value 1.8kΩ 68Ω 22Ω 4-Band Code (1%) brown grey red brown blue grey black brown red red black brown 5-Band Code (1%) brown grey black brown brown blue grey black gold brown red red black gold brown May 2009  65 Below: the PC board is “hung” off the lid of the case on M3 x 25mm tapped metal spacers and secured using M3 x 6mm screws. Note the “extension” leads attached to the switch terminals. At right is the view inside the case with the output terminals mounted and wired back to the board. If you want to build the unit with the highest possible precision and performance, this can be done by using the BQ or KQ versions of the AD588. You may be able to order these from Futurlec but be warned: the BQ version is considerably more expensive than the AQ version we have specified and the KQ version is probably much more expensive as well. Construction Apart from the output terminals, virtually all the components are mounted on a single PC board measuring 84 x 53.5mm and coded 04305091. This fits inside a diecast aluminium box (111 x 60 x 54mm), which provides both shielding and physical protection. The output and remote sensing terminals are all mounted on one end of the box, while the internal/external sensing switch (S1) is mounted directly on the lid, with short wire leads connecting it to the PC board – see photos. The PC board itself is mounted on the back of the lid and is supported via four M3 x 25mm tapped metal spacers. Unlike switch S1, the power indicator LED (LED1) mounts directly on the board and protrudes through a hole in the lid. Fig.3 shows the parts layout on the PC board and the external wiring. Note that trimpot VR1 is optional, as mentioned earlier. Note also that IC1 should not be soldered directly into the board but plugged into a highquality 16-pin DIL socket. Begin the assembly by installing the single wire link on the board, then fit the five fixed resistors, followed by the Voltage Standards: A Brief History From 1905 to 1972, the national standard of EMF or voltage used by the USA was the Weston Cell, a wet chemical primary cell or “battery” developed in 1893 by Edward Weston, of Newark in New Jersey. Weston had improved on an earlier “voltage standard” cell which had been invented by English engineer Josiah Latimer Clark in 1873. Weston cells were adopted as the International Standard for EMF/voltage in 1911. Weston’s cell had a cadmium-mercury amalgam anode, a pure mercury cathode, a paste of mercurous sulphate as the depolariser and a saturated solution of cadmium sulphate as the electrolyte. It was built in an H-shaped glass container, with the anode at the bottom of one “leg” and the cathode in the other leg. The electrical connections to the two electrodes were made by platinum wires fused through the glass at the bottom of the legs. The Weston cell provided an accurate 1.0183V reference with a very low temperature coefficient – much lower than Clark’s earlier cell. However, like the Clark cell, it 66  Silicon Chip could supply virtually no current and could only be used to provide a reference voltage for high-resistance measuring circuits like the classical “potentiometer” (a kind of bridge which compared a known proportion of an unknown voltage against the reference voltage, so no current flowed when the two voltages were “in balance”). Weston cells were used as the US and International standards for EMF/voltage until 1972, when a new standard came into use: the Josephson Junction Voltage Standard (JJVS). This operates on a very different principle: the phenomenon of quantum-mechanical tunnelling currents which flow between two weakly coupled superconductors separated by a very thin insulating layer. This is known as a Josephson junction and the current is known as the Josephson current – after British physicist Brian David Josephson who had predicted the effect in 1962. An improved version of the JJVS was subsequently developed In the 1980s: the Josephson Array Voltage Standard or JAVS. By the way, because Josephson junctions and arrays depend on superconductivity for their operation, they must be operated in a liquid nitrogen environment at 77K (-196°C). Essentially, a JAVS forms a frequency-tovoltage converter, whose conversion factor is exactly reproducible (the agreed figure is 0.4835979GHz/μV). Because frequency can be measured extremely accurately using caesium-beam and caesium fountain standards, the JAVS therefore provides a practical voltage standard of similar accuracy. In fact, the estimated accuracy of current JAVS 10.0V voltage standards is typically quoted as ±0.017ppm. More information on the Weston Cell can be found in Weston’s original US patent (No. 494,827), available on the US Patent Office website. Further information on the Josephson effect, JJVS and JAVS standards can be found on http://en.wikipedia.org/wiki/ Josephson_effect and at http://www. nist.gov/eee1/ siliconchip.com.au B B 70 22.75 44.5 C 15 20.5 E D CL 11 22.75 B B LID, VIEWED FROM ABOVE three non-polarised MKT capacitors. The four electrolytic capacitors can then go in. Be sure to orientate these as shown in the overlay diagram and note that the two 2200μF electros are mounted on their side, with their leads bent at right-angles to go through their respective holes in the PC board. Follow these parts with diodes D1 & D2 and zener diodes ZD1 & ZD2. LED1 can then be installed. It mounts vertically with the bottom of its plastic body about 22mm above the board surface. Be sure to install all these parts with the correct orientation. If you are going to use optional trimpot VR1, it can also now be fitted. It must be installed with its adjustment screw at lower left (this is to align it with the adjustment hole drilled in the lid). The PC board assembly can now be completed by installing the DC power socket (CON1) and the socket for IC1. Orientate the socket with its notched end towards the right, as shown in Fig.3. Leave IC1 out for the time being. Preparing the case Fig.4 shows the drilling details for the case. Note that the larger holes are best made by using a small pilot drill to start with and then carefully reaming each hole out to its correct size. Once you have drilled all the holes, mount the output terminals in place and tighten their mounting nuts firmly to prevent them from later coming loose. That done, solder a short length (say 75mm) of insulated hookup wire to the solder spigot at the rear of each terminal, ready to make the connections to the PC board. siliconchip.com.au ALL DIMENSIONS IN MILLIMETRES CL HOLES A: 9.0mm DIAMETER HOLES B: 3.0mm DIAMETER, CSK HOLE C: 5.0mm DIAMETER HOLE D: 3.0mm DIAMETER HOLE E: 6.0mm DIAMETER CL A A 16.25 10 A 19 A A 9.5 LEFT-HAND END OF BOX 9.5 RIGHT-HAND END OF BOX Fig.4: the drilling details for the case. Use a pilot drill to start the larger holes then step the up to the correct size using a larger drill and a tapered reamer. Next, attach the front-panel label to the lid. This label can be made by downloading the artwork from the SILICON CHIP website, printing it out and then covering it with a protective self-adhesive transparent film. Attach the label using a thin smear of silicone sealant, then cut out the holes using a sharp hobby knife. Toggle switch S1 can now be mounted in position on the lid. Tighten its mounting nut firmly, then fit six 15mm lengths of tinned copper wire to its connection lugs (these leads later pass through their corresponding holes in the PC board). Loop the end of each wire through the hole in its switch lug before soldering, to make sure these joints can’t come adrift when the outer ends of the wires are soldered to the board pads. The next step is to attach an M3 x 25mm tapped metal spacer to each corner of the PC board. Secure these using four M3 x 6mm pan-head machine screws, then install the leads between the output terminals and their corresponding PC board pads – see Fig.3. IC1 can now be plugged into its socket. Be sure to orientate it correctly and make sure that all its pins go into the socket – ie, not down the outside of the socket or folded under the IC itself. The PC board can then be attached to the lid. Note that the extension wires fitted to switch S1 must all pass through their matching holes in the PC board, while LED1 must pass through its corresponding hole (C) in the lid. Secure the board to the lid using four countersink-head M3 x 6mm screws, then solder the six switch leads to their board pads. The unit can now be completed by May 2009  67 STIC FANTAIDEA GIFT UDENTS FOR SFT ALL O S! AGE THEAMATEUR SCIENTIST An incredible CD with over 1000 classic projects from the pages of Scientific American, covering every field of science... NEW VERSION 4 – JUST RELEASED! GET THE LATEST VERSION NOW! Arguably THE most IMPORTANT collection of scientific projects ever put together! This is version 4, Super Science Fair Edition from the pages of Scientific American. As well as specific project material, the CDs contain hints and tips by experienced amateur scientists, details on building science apparatus, a large database of chemicals and so much more. 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Study the physics of spinning tops ! Build an apparatus for studying chaotic systems ! Detect metals in air, liquids, or solids ! Photograph an ant's brain and nervous system ! Use magnets to make fluids into solids ! Measure the metabolism of an insect . . . ! and many, many more (a thousand more, in fact!) See the V2 review in SILICON CHIP, October 2004. . . or read on line at siliconchip.com.au This is the ALL-NEW Version 4 . . . it’s even BETTER! HERE’S HOW TO ORDER YOUR COPY: BY PHONE:* BY FAX:# (02) 9939 3295 9-5 Mon-Fri <at> (02) 9939 2648 24 Hours 7 Days BY EMAIL:# silicon<at>siliconchip.com.au 24 Hours 7 Days BY MAIL:# BY PAYPAL:# PO Box 139, Collaroy NSW 2097 silicon<at>siliconchip.com.au 24 Hours 7 Days * Please have your credit card handy! # Don’t forget to include your name, address, phone no and credit card details. BY INTERNET:^ siliconchip.com.au 24 Hours 7 Days ^ You will be prompted for required information There’s also a handy order form inside this issue. Exclusive in SILICON Australia to: CHIP siliconchip.com.au 68  Silicon Chip siliconchip.com.au fastening the lid/PC board assembly to the box using the screws supplied. Internal & External Sensing Connections Using it There are no adjustments to be made to the Precision Voltage Reference if you don’t have access to a very high precision voltage source to calibrate it against. As stated previously, without calibration, it will operate with better than ±3mV precision, as provided by the AD588AQ chip itself. In that case, it’s merely a matter of switching S1 to the internal sensing position and applying power (12V AC) to CON1. LED1 should light immediately to show that the unit is operating and 10.000V ±3mV will now be available at the upper output terminals, ready for checking your DMM or whatever. This “internal sensing” configuration is the one to use for most simple jobs like DMM calibration, with the DMM input leads connecting directly to the Precision Voltage Reference’s upper output terminals. Cable compensation The only occasions when it’s preferable to use external sensing or “Kelvin connections” will be when you are supplying the unit’s voltage to a load at the end of a cable and the load is drawing sufficient current to introduce a significant voltage drop due to the cable resistance. In such situations, you’ll need to extend the output sensing terminals of the Precision Voltage Reference to +OUT 10.00 +SENSE INT DC VOLTS EXT SENSING DMM –OUT – –SENSE + PRECISION VOLTAGE REFERENCE A LOCAL MEASUREMENT, INTERNAL SENSING DMM LONG CABLES 10.00 DC VOLTS +OUT +SENSE INT EXT SENSING – LOAD –SENSE PRECISION VOLTAGE REFERENCE B REMOTE MEASUREMENT, EXTERNAL 'KELVIN' SENSING Fig.5: how to connect the Precision DC Voltage Reference for both local (A) and remote (B) measurements (the latter compensates for cable losses). the load end of the cable via a second pair of leads as shown in Fig.5. Then S1 is switched to the external sensing position, so that the AD588 senses the output voltage right at the load end of the cable rather than at its own end. As a result it will maintain the load voltage at the correct 10.000V, compensating for the cable drop. All of the foregoing also applies if you build the unit with trimpot VR1 and/or use an AD588BQ/KQ for higher precision. The only complication in these latter situations is that you’ll need to compare the output of the Precision DC Voltage Reference with a higher precision source and adjust VR1 to trim its output as close as possible to 10.0000V before you can put SC it to use. Australia’s Best Value Scopes! Shop On-Line at emona.com.au GW GDS-1022 25MHz RIGOL DS-1052E 50MHz RIGOL DS-1102E 100MHz 25MHz Bandwidth, 2 Ch 250MS/s Real Time Sampling USB Device & SD Card Slot 50MHz Bandwidth, 2 Ch 1GS/s Real Time Sampling USB Device, USB Host & PictBridge 100MHz Bandwidth, 2 Ch 1GS/s Real Time Sampling USB Device, USB Host & PictBridge Sydney Brisbane Perth ONLY $599 inc GST Melbourne Tel 02 9519 3933 Tel 03 9889 0427 Fax 02 9550 1378 Fax 03 9889 0715 email testinst<at>emona.com.au siliconchip.com.au + –OUT ONLY $879 inc GST Tel 07 3275 2183 Fax 07 3275 2196 Adelaide Tel 08 8363 5733 Fax 08 8363 5799 ONLY $1,169 inc GST Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA May 2009  69