Each report about an item of electronic test equipment is based on examination and operation of the device in the ELECTRONIC SERVICING laboratory. Personal observations about the performance, and details of new and useful features are spotlighted along with tips about using the equipment for best results.
By Carl Babcoke, CET
Hickok model LX-304 is a portable five-function digital multimeter measuring
only 5 7/8" x 3 3/8" x 1 3/4" and weighing 12 ounces.
Model TP-20F temperature probe tests between -67F and +300F. Each milli volt at the output represents one degree F, when plugged into a DMM capable of 1mV resolution.
Each LX304 is equipped with a plastic cover that protects the meter and secures the test probes. An optional CC-3 zipper-opening case offers additional protection.
Portable digital multimeter
A rugged, portable DMM is model LX-304 from Hickok. Be tween 200 and 300 hours of intermittent operation can be obtained from each 9V battery. The test leads store under the removable protective lid. Accidental application of 120Vac to any voltage or resistance range does not damage the meter.
The sliding switches are arranged for convenient one-hand operation of all ranges. The readout is a 1/2-inch 3 1/2-digit LCD display with automatic-polarity indication, automatic decimal, automatic low battery and over-range indications, and automatic zeroing. A few seldom-used functions have been deleted. These include ac current and low-voltage ac.
Specifications
Five dc-voltage ranges cover 200mV full-scale to 1000V full scale with ± 0.5% plus 1-digit ac curacy and an input impedance of 10m-O. Ac-voltage ranges of 200V and 600V RMS full-scale are rated at 4.3M-ohm input resistance with ac curacy of 1.0% plus 4-digits. Frequency response begins to roll-off above 1000Hz, reaching -1dB at about 1800Hz.
Resolution of 0.1mA is obtained on the 200mA and 1A dc-current ranges. Accuracy is rated at 1.5% plus 1 digit.
Six low-power resistance ranges cover 200 to 20M ohm full-scale with about 0.3V across the test leads at maximum readings. In addition, the 20K range can be used to test transistor junctions and diodes, after a sliding switch near the Hickok name on the panel is moved to the up position (that exposes a red color). Although this function applies a higher dc voltage to force forward-biased solid-state junctions into partial conduction, it is not a high-power ohms function.
The action has been tailored to show comparative readings of diodes and has non-linear response.
Readings can be obtained on all ranges when the diode-test switch is turned on, but these readouts are not correct for resistance measurements. Therefore, be sure to turn off the diode-test sliding switch before measuring pure resistances.
Accessories
Many accessories are available for Hickok model LX-304. These include a padded carrying case, 10A current shunt, ac adapter, RF probe, 10kV probe, 40kV HV probe and a temperature probe.
Temperature probe and adapter Model TP-20 is a probe and adapter system that can be used with any DMM (including LX-303 and LX-304) having a 200mV range. The temperature-measuring system is powered by one 9V battery and it measures -67F to +302F (or -55C to 150C for model TP-20C) at an accuracy of ± 2.3F.
Comments
Hickok model LX-304 DMM has the functions and durability for either field or bench-top servicing.
Accuracy is more than adequate for these applications. The sample meter showed only slightly higher readings than three other meters rated at 0.1%. The digital read out responded faster than most, giving about three updated readings per second.
Figure 1--Weston model 6000 digital multimeter has autoranging to provide
26 ranges in nine functions. Functions and some ranges are selected by a rotary
switch, while ac or dc readings are selected by the ac/dc switch.
Figure 2. The range plate can be removed by fingernail, to make accessible
the two 9V batteries, the fuse and all calibration adjustments.
Autoranging DMM
Weston model 6000 is an auto ranging digital-readout multimeter featuring nine functions in 26 ranges. Measurements are displayed on a 3 1/2 -digit 0.5-inch LCD readout (Figure 1). The same two input jacks are used for all measurements except 10A of current. A sliding switch provides dc or ac readings for both voltage and current. In addition, the rotary 7-position switch selects six functions and power off (Figure 1). Other ranges are selected by the autoranging.
Decimal placement, zeroing and polarity indication are all automatic.
A separate hold input jack is provided for a frozen reading.
Continuity between the hold jack and the common test-lead jack prevents the reading from changing. The optional test leads have wires and hold switch ready for use.
A manual range-hold switch (that freezes the autoranging) and a backlight switch (for readings in the dark) also are optional.
Other accessories include: a 50kV HV probe; RF probes to 520MHz; a vinyl carrying case; clamp-on ac current probe for readings to 200A; and a light-meter attachment.
Two standard 9V batteries pro vide up to 350 hours of intermittent operation. The range plate can be removed without tools to permit installation of the batteries (Figure 2) or for fuse replacement. This also exposes the calibration adjustments.
The carrying handle serves also as a tilt stand or a protective cover for the LCD display (Figure 3). Accuracy ratings Dc voltages from 00.1mV and 199.9mV are selected manually by rotating the function switch to the mV position. Four auto-ranged dcV ranges are selected by the V position. Input impedance is 10M-o for all ranges and the accuracy is rated at 0.35% of reading ±.1 digits.
The acV ranges are the same; however, the input impedance is 9M-o and the 40Hz-to-400Hz ac curacy is rated at 0.5% of reading +- 5 digits. On the 20V RMS range, the frequency response measured about -1dB at 120kHz (very good for audio work). The 1000V range has less bandwidth. Readings are RMS for sine waves only.
DC current has a rating of 0.75% of reading E3 digits, while the rating is 1.5% of reading ±5 digits for ac current.
There are three resistance ranges.
The C2 range reads from 00.1 to 199.9 ohm with accuracy of 1% of reading ±/ digits. The k-o range extends from .001K-o to 199.9K-o with 0.5% of reading ±1 digit accuracy. The M-o range measures from .001 M-o to 19.99 M-o with rated accuracy of 0.5% of reading digit.
All resistance ranges are low power, with 5V for an open circuit or less than 0.2V during measurements. Red test lead was positive for all ranges except the low 0 range, where it was negative relative to the black (common) lead. This must be remembered when testing the forward resistance of diodes.
Figure 3--The carrying handle can be used as a tilt stand or a protective
cover for the display. Banana plugs for the test leads are located on one
side.
Comments
Weston model 6000 auto-ranging digital multimeter performed well, giving higher accuracy than specified.
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