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Fluke 45 Dual Display Digital Multimeter Fluke's model 45 multimeter is not just an ordinary benchtop instrument - it is a multipurpose instrument that can be used in service workshops, research and development laboratories and production lines. By LEO SIMPSON You know how it is when you are set up to do measurements on a piece of equipment. Say you're measuring an audio source such as a power amplifier. You may want to measure AC output voltage, DC offset voltage, signal frequency, frequency response (in decibels) and so on. Before you know it you have several instruments hooked up to the audio source in question and an unholy mess of test leads. With the Fluke 45 hooked up instead, the test set up is greatly simplified. For example, without changing the connections, you can measure and display the AC output voltage and the signal frequency (anywhere up to 1MHz). Press a few buttons, and the Fluke will display both the power output and the frequency response in decibels. With the test setup still operating, you can boot up your computer and use it to control a series of measurements which can run for as long as you like - an hour, a day, or weeks on end. And you can control the rate at which measurements are recorded and stored on disc, for later recall. The above description gives just a brief insight of what can be done with the Fluke 45 dual display multimeter. We don't propose to cover all the features of the Fluke since it would take more pages than there are in this magazine. In fact, the instruction manual for the unit runs to 120 quarto pages while the manual accompanying the Quickstart 45 software is another 65 pages. So this article really will just amount to a general overview of the instrument. Features As it comes out of the box, the Fluke 45 is a medium size instrument with a light beige coloured case and a contrasting dark Perspex window through which the displays can be seen. It has four recessed jack sockets, the two on the lefthand side being for most measurements while the other two are for current (10 amps and 100mA). In addition, there are 17 touch buttons which control all the meter's functions. On the left, six of the buttons have symbols to indicate Volts DC, Volts AC, Amps DC, Amps AC, Ohms and Diode (Continuity) test. All of these modes are autoranging, which means that the meter automatically selects the range for best reading indication. If you want to lock the meter onto one range, you just push the Auto button; you can then step up or down through the ranges by pushing the Hi or Lo buttons. True RMS measurements How do you get a multimeter to give a reading when no leads are connected? In this case, the Fluke 45 is picking up an internally generated signal at 26kHz. The instrument features a green vacuum fluorescent readout. 18 SILICON CHIP A feature of the Fluke 45 is that it gives true RMS measurements for AC voltages and currents. This is in contrast to the vast majority of meters which are average respon- T~e Fluke 45 is_ shown here con~rolled by an IBM PC (ye~, a genuine true-blue) via the RS-232 interface and Qmckstart software. Both displays are in use on the readout and the measurements are also being recorded on the monitor screen. ding and indicate the RMS value for sinusoidal (ie, sinewave) waveforms only. This means that for all except sinusoidal waveforms, these other meters will always have a reading error. The Fluke doesn't, even for quite complex waveforms. In addition, if the AC volts and DC volts buttons are pressed simultaneously, the Fluke 45 will take a DC measurement and an AC measurement and then display the calculated RMS value. Cancelling lead resistances Ever found that the resistance of your measuring leads caused errors when measuring low resistance values? The Fluke can solve that problem with its RELative mode. Just touch the two leads together and press the REL button. This zeros the display and it can then accurately display the resistance to be measured. Of course, the REL mode is available for all measurement modes and comes in very handy when you have to make a lot of readings to establish trends. Second display The real power of the Fluke 45 is that it has a second 5-digit display which provides every measurement function available on the primary display. The only practical difference is that while the primary display can have auto or manual range selection, the secondary display is autoranging only. Because the second display duplicates all the functions of the primary display, it effectively is two 5-digit multimeters in one. Sample rates Often measurements can be made inaccurate by the amount of noise superimposed on the lines being measured. The Fluke can help overcome that too by varying the rate at which the measurements are made, at 2.5, 5 or 20 readings per second. The rate is shown on the display with an "S" (slow), ''M" (medium) or "F" (fast). Varying the rate to get rid of noise and jitter on measurements does have a down side though because it varies the resolution. Maximum resolution is obtained at the slowest sample rate. At the slow setting, maximum resolution is 100,000 count (ie, 5 digits); at the medium ·setting, maximum resolution is 30,000 count while at the fast setting it is 3000 count, equivalent to typical 3 ½-digit meters. Accuracy Resolution is not to be confused with accuracy, of course, and as continued on page 117 SEPTEMBER 1990 19 Dick Smith Electronics, Bowen & Ruthven Sts, Toowoomba, 4350. Phone (076) 38 4300. Dick Smith Electronics, Kings Rd & Woolcock St. Townsville, 4810. Phone (077) 72 5722. Dick Smith Electronics, Cnr Pacific Hwy & Kingston Rd , Underwood, 41 19. Phone (07) 341 0844. Jaycar Electronics, 144 Logan Rd, Buranda, 4102. Phone (07) 393 0777. SOUTH AUSTRALIA Dick Smith Electronics, 252 Pulteney St, Adelaide, 5000. Phone (08) 232 1200. Dick Smith Electronics, 688 Port Rd , Beverley, 5009. Phone (08) 347 1900. Dick Smith Electronics, 1267 South Rd, St Marys, 5042. Phone (08) 277 8977. Dick Smith Electronics, Shop T25, Elizabeth City Centre , 5113. Phone (08) 255 6099 . Dick Smith Electronics, Main North Rd & Darlington St, Enfield, 5085. Phone (08) 260 6088. Eyre Electronics, 15 Forsyth St, Whyalla, 5600. Phone (086) 45 4764. Force Electronics, 203 Wright St, Adelaide, 5000 . Phone (08) 212 5505. Force Electronics, 500a Brighton Rd, Brighton, 5048. Phone (08) 377 0512. Force Electronics, 24 Beach Rd , Christies Beach, 5165. Phone (08) 382 3366. Force Electronics, 445 Main North Rd, Enfield, 5085. Phone (08) 349 6340. Force Electronics, 127 Findon Rd, Findon, 5023 . Phone (08) 347 1188. Force Electronics, 5 Somerset Circuit, Lonsdale, 5160. Phone (08) 326 0901. Microtronics, 305 Morphett St, Adelaide , 5000. Phone (08) 212 1799. Selectronics, BI LO Shopping Centre, Mannum Rd, Murray Bridge, 5214. Phone (085) 31 0445 WESTERN AUSTRALIA Altronics, 17 4 Roe St, Perth, 6000. Phone (09) 328 1599. Dick Smith Electronics, Wharf St & Albany Hwy, Cann ington, 6107. Phone (09) 451 8666. Dick Smith Electronics, 68 Adelaide St, Fremantle, 6160. Phone (09) 335 9733 . Dick Smith Electronics, William St & Robinson Ave, North Perth, 6006. Phone (09) 328 6944. Dick Smith Electronics, Raine Square, 125 William St, Perth City, 6000. Phone (09) 481 3261. Today's Electronics, 295 Hannan St, Kalgoorlie , 6430. Phone (090) 21 5212. TASMANIA Dick Smith Electronics, Shop 48, Lower Level, Cat & Fiddle Arcade , Hobart, 7000. Phone (002) 31 0800. Fluke 45 Digital Multimeter with all digital multimeters the accuracy of any measurement is always less than indicated by the resolution. As you would expect, the Fluke gives its best accuracy on DC measurements: ± .02%. For DC current and resistance, the accuracy is generally ± .05 % while for AC voltage and current, the accuracy varies depending on the signal frequency. Interestingly, the Fluke 45 can tolerate quite high peak AC voltages when measuring DC voltage. For example, on the 100mV to 1000mV DC range, the maximum allowable peak AC is 20 volts. For the 10V to 1000V DC ranges, the maximum allowable peak AC is 1000 volts. Production line use The Fluke 45 is ideally suited to production line use where it is necessary to check that unit parameters are within limits. You can set the upper and lower limits and then the Fluke will indicate the reading on the primary display, together with a Hi, Lo or Pass indication on the second display. This is handy where unskilled operators are responsible for the testing. Computer control Finally, the other major feature of the Fluke 45 is that it can be controlled by a computer using either the built-in RS-232 interface or optional IEEE-488 interface. Also available is a floppy disc with a full range of commands. Called ctd from p.19 "Quickstart 45", it operates on any IBM or compatible machine using DOS 2.1 or later. We put through a range of control functions and found that it works very well. You can vary the rate at which measurements are made (anything from 1 per second upwards) and stored to disc for later analysis - a very powerful tool. Summing up As noted at the beginning of this article, we have space only for a brief overview of this instrument. It is a highly flexible and accurate laboratory instrument, easy to use for most functions and supported by a very well written instruction manual. For any workshop or laboratory wanting a highly flexible ,multimeter with a step-up in facilities over Fluke's fine 80 series meters, the model 45 is the one to go for. Best of all, all that measurement capability comes pretty cheaply. It is priced at $1216 plus tax. The Quickstart 45 software is available at $200 plus tax, the optional IEEE interface at $310 plus tax, and the battery pack at $245 plus tax. Also available is a convenient padded vinyl carrying case priced at $100 plus tax. For further information contact Philips Test & Measurement, 25-27 Paul St, North Ryde , NSW 2113. Phone (02) 888 0416 or contact Tech-Fast T&M Pty Ltd, 14B Maxwell St, Turramurra, NSW 2074. Phone (02) 988 3865. ~ Is Your Product Getting The Exposure It Deserves? NORTHERN TERRITORY Dick Smith Electronics, 20 Stuart Hwy, Stuart Park, 0820. Phone (089) 81 1977. Also at most newsagents throughout Australia. Our newsagency distributor is Network Distribution Company which has offices in every state capital. Back issues of SILICON CHIP are available from Silicon Chip Publications Pty Ltd. See the back issue page elsewhere in this issue. Electronics retailers who would like to sell SILICON CHIP should contact our Sales Manager, Paul Buchtmann, on (02) 979 5644 or write to us at SILICON CHIP, PO Box 139, Collaroy Beach, 2097. Consumers need to see your product if you want them to buy it Contact Paul To Reserve This Space - (02) 982 9553 SEPTEMBER1990 117