Fullscreen HTML5Med Res (??MB)HTML4

PRODUCT SHOWCASE Yokogawa's 5-digit DMMs have true RMS measurement These new meters from Yokogawa have a 5-digit readout and very high accuracy for handheld instruments. They also provide true RMS measurements for AC voltage & current, and they have a new safety feature in the form of a shutter which prevents connection of probes into the terminal sockets unless the current ranges are selected. Superficially, the new Yokogawa 7544 01 multimeter does not look a great deal different from most other meters on the market. It is not until you turn it on that you realise that it is substantially different because it has a 5-digit liquid crystal display with a maximum display count of 49,999. This new high resolution display together with a basic accuracy of ±.05% +2 counts ( on the 500mV range) means that handheld digital multimeters have been shifted to a new level of precision - at least for those made by Yokogawa. True RMS measurements As well, the two top models in the Yokogawa range have true RMS measurement for AC voltage and current. By contrast, the vast majority of multimeters have "average value" indica­ t ion for AC measurements. This means that their measurements are accurate only when the voltage or current wave­form is a sine wave. For other wave­forms such as square, sawtooth or rec­tified sinewave, their readings will be inaccurate. Yokogawa's true RMS measurement applies for AC waveforms with a crest factor of less than three or less than six for readings of less than half full scale for any AC voltage or current range. (Crest or peak factor is the ratio of the peak to the RMS value of a waveform). In addition, it will read the true RMS values of AC voltages and currents up to 30kHz (100kHz for the model 7544 02). although the accuracy is degraded for the higher frequencies. Safety lock shutter These days with all the measurements engineers and technicians have to make when designing and repairing equipment, it's so easy to plug the probes into the wrong sockets, select the current range and then either blow the fuse or damage the multimeter and even the gear you're work­ing on. Some multimeters give you an audible warn­ing that you have selected the wrong range for the terminals in use but it is still possible to do the wrong thing and cause damage if you are not paying attention. To combat this problem, Yokogawa have come up with a "safety shutter" for the current terminals. This slides over the terminal openings, thereby preventing you from inserting a banana socket probe. To open the shut­ter, you must first select a current range with the range switch and then you can push the slider upwards. Once the shutter is open, you can only select different current ranges; if you want to select one of the other ranges you must first remove the probes and close the terminal shutter. Both current terminals are fused, with the 10A range having a 15A 600V fast acting cartridge fuse. Incidentally, the back the multimeter is removable after you undo the four screws and importantly, these screws run into integral pillars with threaded brass inserts. Some quite expensive multimeters do not have threaded metal inserts and conse­quently it is quite easy to strip the threads after the screws have been removed several times. And after all, over the life of the meter you will have to remove the back quite a few times to replace the batteries, unless of course, they are in their own com­partment. July 1994  77 Universal device programmer The Power-100 has been designed to meet the demand for a universal programmer with a built­ in power supply and PC printer port connection. It is intended for development and volume production and ISO 9000 requirements for customer calibration and test­ ing have been met. Since a programmer must cope with many new devices, the ability to upgrade is important for most customers. The software can cope with "self definition" which is ideal for ASIC devices and there is pro­vision for chips with up to 256 pins. Some of the features are as follows: 48 pin Textool socket as standard – each of the pins are programmable, including GND, VCC, VHH, VOP, clock oscillator, quick pull up and protection driver etc; a full range of adaptors to And this brings us the next feature. Instead of the usual 9V alkaline battery, this meter uses two 1.5V AA cells which have the advantage of being cheaper. Battery life is quoted as 120 hours with alkaline cells being used. Naturally, the unit has auto­matic switch off to conserve the bat­teries. This operates 30 minutes after the last switch operation but gives an audible beep warning 30 seconds be­ fore it signs off. Interestingly, although the battery voltage is 3V, the DMM apparently has an internal step-up converter. This cover a wide range of packages; up to 8- gang programming for production use; rapid programming – 27C256 in 6 seconds; over 1500 devices supported – manufacturer ap­ proved algorithms; FlashE/ EPROM, PLD, PAL, PEEL, GAL, MAPL, MAX, MACH, bipolar & serial PROM, MPU/MCU; test and allows it to develop an open circuit voltage of more than 5.5V for diode and continuity tests. This means that it will readily test light emitting diodes and other semiconductors with a high forward bias voltage. However, Yokogawa have gone one step further to cater for in-circuit resistance measurements. In this instance, a high open circuit voltage is a problem because semiconductor junctions will conduct and falsify the reading. To overcome this situation, you select the "LP#" mode which has an open circuit voltage of just 0.2V, CALLING ALL HOBBYISTS We provide the challenge and money for you to design and build as many simple, useful, economical and original kit sets as possible. We will only consider kits using lots of ICs and transistors. If you need assistance in getting samples and technical specifications while building your kits, let us know. YUGA ENTERPRISE 705 SIMS DRIVE #03-09 SHUN LI INDUSTRIAL COMPLEX SINGAPORE 1438 TEL: 65 741 0300    Fax: 65 749 1048 78  Silicon Chip identify TTL & CMOS LOG IC, SR AM, DRAM, SIMM/SIP & logic vector; and cus­tomer calibration and self-diagnosis to meet ISO 9000. For further information, contact Nucleus Computer Services Pty Ltd, 9B Morton Ave, Carnegie, Vic 3163. Phone (03) 569 1388 or fax (03)569 1540. low enough not to be a problem with semiconductors. Other features As can be seen from the photo, the Yokogawa meter has a large rotary function switch which selects the parameter to be measured, eg, current. You then use the Select button to se­lect AC or DC measurement. For AC and DC voltage measurements, the unit has auto ranging and auto polar­ity indication but you can also manu­ally select ranges using the Range but­ton. We should point out that normal operation of the DMM is a full 50000 (actually 49,999) but you if you don't want your measurements to have this order of resolution you can suppress the least significant digit by pressing the "5000" button to give a 4-digit mode. The Data-H key will store and hold the present reading on the display while the Min/Max key, as you might expect, will store and display minimum and maximum values but will also calculate and display an average (AVG) value. Finally, the REL key ze­ros the existing reading on the display and then shows relative measurements. Inter- estingly, it also provides the facility to cancel out test lead resistance on the low resistance ranges thus giving better accuracy. Frequency & decibels Apart from its 5-digit display and high accuracy, the Yokogawa 7544 01 is the first handheld multimeter that we know of to feature measurements in decibels for AC voltage. Actually, you can measure in dB or dBm (deci­bels relative to 775mV or 1mW into a 600W load). When you select the AC voltage function, you can measure volts or millivolts depending on amplitude, dBm or the frequency, by pressing the Select button. You can also have a display which alternates between frequency and volt­ age at 6-second intervals. To measure in dB as opposed to dBm, the REL key must be pressed. The frequency range of the multimeter is from 10Hz to 999.9kHz. Accuracy As already noted, the model 7544 01 has an accuracy of ±.05% + 2 counts for the 500m V DC range, while for the other DC voltage ranges (5V - 1000V) it is ±.07% + 2 counts. For AC voltage, the accuracy for all ranges (500mV 750V) is ±1 % for frequencies be­tween 40Hz and 50Hz; ±0. 7% between 50Hz and lO0Hz; ±0.5 between 100Hz and 2kHz; ±1 % between 2kHz and 10kHz; and ±2% between 10kHz and 30kHz. AC current accuracy is ±1%for frequencies between 40Hz and 1kHz. Well, how to conclude? This re­view really can't do full justice to a product with so many features but it should indicate that the Yokogawa 7544 series really has set a new stand­ard for accuracy, resolution and oper­ ating features. We are impressed. Recommended retail price for the model 7544 01 is $679 plus sales tax, while the higher accuracy model 7544 02 is $998 plus sale tax. For further information, contact Yokogawa Australia Pty Ltd, 25 Paul St, North Ryde NSW 2113. Phone (02) 805 0699. Frequency synthesiser for PCs Capable of ultra-wide frequency synthesis, the FSC-30 and 50 are half length cards for any PC-XT/AT/386 and provide up to two independent TTL level programmable square wave generators at low cost. Both models come with one or two synthesisers per card, with each channel being independent from the other, and crystal controlled for excellent stability. An optional external reference input is also available, with the reference source being jumper selectable between external or on-board frequency source. Software supplied with the cards provides either command line or popup menu selection of output frequency. Driver software is also sup­plied, with source code, for writing custom programs and an example pro­gram is included. The FSC-30 has a range of 0.024Hz to 30MHz while the FSC-50 has a range of 2.98Hz to 50MHz, with reso­lution for both being 27,000 steps per decade. The cards have three switch­able addresses for multiple card use and are connected via 50W coax with BNC connectors. For further information, contact Boston Technology Pty Ltd, PO Box 1750, North Sydney, NSW 2060. Phone SC (02) 955 4756. Power saving 486 processors from Texas Instruments Texas Instruments has announced a range of 486 chips designed for the PC manufacturing market. Designated the TI486DLC and TI486SLC, the new devices offer many advanced features. The TI486SLC is designed as a notebook device and offers 5V or 3V operation, saving up to 60% in power consumption for the CPU alone. When a portable based on the 486SLC has not been in use for some time, the CPU enters a special standby mode where power consumption is virtually zero. The TI486DLC version has a full 32-bit external data bus offering all the power and facilities de­manded by "Desktop" systems. As well, they offer the same circuit board footprint as existing 386 chips, allowing a manufacturer to upgrade older designs with only minimal changes. Both devices utilise a pipelined architecture to optimise instruction execution and thus improve perlormance. In addition, an on-chip data cache cuts data reads from main memory by up to four clock cycles. The TI devices also feature a built-in hardware multiplier that speeds up maths intensive applications such as CAD. For further information, contact Texas Instruments Australia Ltd, 17 Khartoum Rd, North Ryde, NSW 2113. Phone (02) 910 3100 or fax (02) 878 2489. July 1994  79