The Fluke 289 is an all-purpose DMM (digital multimeter) designed for electricians and technicians. It provides the usual measurement functions, such as V a.c., V d.c., ohms, capacitance, A a.c. and A d.c.
The meter has the ability to monitor a circuit while the user is busy elsewhere. For example, a technician can set the meter up to record AC voltage on a circuit of concern and then exercise loads at a remote location on that circuit. Returning to the meter, he can then view a TrendCapture display of the circuit’s performance during the exercise. The saved data appears as a strip chart-like recorder display on the face of the meter.
This kind of logging helps evaluate switching events and sudden load changes. If a permanent record of the process is needed, the results can be saved in memory for later transfer to a computer. In contrast to many other DMM logging systems, the 289 has the ability to instantly see the history of a test, on screen, while still on site. It can also identify and save multiple recording sessions, without returning to a PC to download the results each time.
The meter features a 50 Ω function with the ability to measure low resistances with 0,001 Ω resolution. With a two-wire measuring system, this allows the technician to short the test leads together and use the REL mode to zero out test lead resistances. Then, firm connections can be made to the test points, such as the stator winding of an induction motor, and the winding resistance can be read. By comparing the resistances of the stator windings, the user can uncover internal connection problems that may contribute to reduced motor performance or impending failure.
Another feature is the fact that the measuring circuit in this function uses a much higher measurement current than normal ohms functions, with an available voltage up to 20 V. For the industrial technician, who often works in high noise environments, this means that the low resistance readings will be more accurate in the presence of that noise, which may easily appear on the circuit of concern.
LoZ AC volts is a safety and accuracy function which clearly identifies live conductors among those showing ‘ghost voltage’ — which appears on unconnected wiring in close proximity to live conductors. The LoZ feature provides a load for the circuit that collapses ghost voltage to a zero reading, indicating that the conductor would be safe to work with. The feature also automatically displays the AC voltage of a live circuit, as well as any DC voltage, in a dual display presentation. Besides the everyday safety of reliable measurements, LoZ is also useful for monitoring residual DC voltage while troubleshooting electronic power controls such as those used for theatrical stage lighting or motor drives.
The V a.c. and mV a.c. functions of the 289 offer a low pass filter feature that reduces the AC measurement bandwidth to 1 kHz and below. Using this feature, a technician can monitor the output voltage and frequency of an adjustable speed motor drive accurately, while rejecting the higher frequency output voltages that often confuse other meters.
For example, sometimes a drive output smoothing filter is installed to protect a motor from those higher frequency voltage components that can result in damaging high peak voltages. In that kind of setup, measuring the unfiltered voltage at the motor can ensure that the filter is effective, by showing that the high frequency voltages are significantly reduced in value. That is indicated when the unfiltered reading nearly equals the filtered reading.
The DMM’s ‘(i) info’ button provides a convenient alternative to the need to carry a manual or reference card around. To use this feature, the user selects the desired function, highlights it in the menu, and presses ‘(i) info’ to see a brief description of the function and its use. It is effectively a manual that is automatically turned to the right page as one moves from measurement to measurement. This feature suggests uses for several of the new features and how to apply them. The info button is also multilingual.
For more information contact Comtest, +27 (0)11 608 8520, [email protected], www.comtest.co.za
| Tel: | +27 10 595 1821 |
| Fax: | +27 11 608 1525 |
| Email: | [email protected] |
| www: | www.comtest.co.za |
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