TEST Instrument REPORT -- Simpson's 420, 454 and 467 -- Reasonably Priced Trio (ET/D, Mar. 1981)

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by Peter B. Credit

------------ Simpson's Models 420, 454, and 467.

Featured in this month's Test Instrument Report are 3 pieces of quality equipment from Simpson that could help equip a starting shop or one that is already operating on a relatively tight budget. The three are the Model 467 3 1/2 DMM, the Model 420 Function Generator, and the Model 454 15MHz Dual-Trace Oscillo scope. The Model 467 incorporates some unique features not found in most other DMM's. The most unique of these features is the combination digital and analog display using an LCD bargraph.

The bargraph reading corresponds to the numerical reading in both the ac/dc volts and ac/dc ma functions. The bar graph reading will follow changes in varying inputs and will display 110% of the range selected. Another unique feature of the 467 is that the pulse detection mode will give visual and/or audible indication (buzzer sound) of either negative or positive pulses and logic states.

The dc and ac voltage range of the Model 467 is 200 mv to 1000 mv with a reported accuracy of ± 0.1% of input ±1 count on dc and ±1.5% of input +5 counts on ac (20-40Hz).

The resistance range is 200 ohm to 20 M-O with a reported accuracy of - ±0.25% ) up to 2000 K-O. The dc current range is 200µa to 2000ma with an accuracy of ±0.5% of input +1 count except the 200 ma and 2000ma ranges which it is said to be ±0.75% of input +1 count. The 20K, 200K, and 2000K ranges have an open circuit voltage of approximately 0.45v, with enables in circuit resistance measurements to be made without turning on semiconductor junctions. The other ranges have an open circuit voltage of approximately 2.4v, which will turn on semiconductor junctions for in-circuit testing. I found the Model 467 pleasant to operate due to its versatility and the unique combination of the analog and digital display.

The price of the 467 is $239.00. Next is the Model 420 function generator that provides sine wave, triangular wave, and square wave output, plus TTL, covering a frequency range of 0.1Hz to 1MHz in seven ranges. The output of the 420 is stated to be 20v_pp open circuit and 10v p-p into 600 ohms (both checked out) with a dial accuracy of ±3% full scale (1Hz to 100kHz), ± 5% full scale overall. The fixed TTL compatible output will drive up to 10 TTL loads with an approximate rise/fall time of less than 25 nsec.

The output impedance of the Model 420 is 600 ohms ± 5%, and the power requirements are 120/220/240 vac for the A model and 4 "C" sized batteries for the D model. Some applications of the 420 include: digital circuit design, communications and telemetry equipment, sound and vibration analysis, high fidelity equipment, signal transducers, control and information display systems, production testing and instrument repair or calibration, some of which are thoroughly covered in the operators manual.

The compact size and weight (3 lbs) of the 420 would be very convenient for field servicing. The price of the Model 420 is $175.00 for the A model, and $210.00 for the D model. Completing the trio of test instruments this month is the Simpson Model 454 3", 15 MHz dual trace oscilloscope. The vertical and horizontal sensitivity of the 454 is 5mv/ div to 10v/div calibrated in 11 steps; accuracy is said to be ± 5%. Maximum input voltage for both ac and dc is 250v dc+ ac peak. With the X10 probe it is 500v (to 1kHz). Features include dual vertical inputs that permit simultaneous viewing of two waveforms plus differential amplifiers from inputs through deflection stages that provide common mode noise rejection for stable wave forms. The 454 displays channel A, channel B, A and B, A plus B, and A minus B. A chopping rate of 100kHz is also provided for low speed waveforms along with triggering--external, channel A or channel B with TV sync position.

The 454 has a 24 µ-sec rise time for display of digital pulses and fast sweeps. I like the compactness of the 454 (4-3/8 x 9-78 x 13-1 / 4") and its weight (13 lbs) and also the pushbutton operation. The only exception I noted to the overall ease of operation was the tightness of the tim/div knob which I thought could have been easier to turn.

The 454 is supplied with two low capacitance X1/X10 probes and opera tor's manual. The price of the Model 454 is $675.00.

(source: Electronic Technician/Dealer)

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