Test Equipment (2018) Flashcards
Name one of the chief causes of test set failure.
Carelessness
Although test equipment is repaired at the intermediate-level maintenance activity, most work performed at this level on test equipment consists of
Calibration
What is the most delicate part of a piece of test equipment?
Meters
List the basic measuring parameters of electronic equipment.
Voltage Current Resistance Power Frequency
What is the most accurate portion of the ohmmeter scale, and why?
The midscale portion of the scale represents the most accurate area because the ohms-calibrated scale is nonlinear
When repairing equipment, you should use a meter with the same sensitivity as specified in schematics and wiring diagrams. What is the reason for doing this?
Because of circuit loading, you should use a meter with the same sensitivity to obtain accurate readings.
Name the piece of test equipment that consists of a hand-driven dc genera- tor, applies a high voltage to the com- ponent under test, and measures current leakage.
megohmmeter or megger
Loading effect is the result of a meter’s sensitivity, and it causes incorrect voltage indications. What relationship exists between a meter’s sensitivity and its loading effect?
the lower the sensitivity of the meter, the greater the loading effect.
What is the major difference between a VTVM and a conventional multimeter?
the VTVM uses a vacuum tube in its input
A phase angle voltmeter is used to determine the overall accuracy of electronic equipment by measuring phase angles. What is actually measured by the phase angle voltmeter?
A phase measuring device must measure the phase difference between 2 discrete frequencies, regardless of the phase and amplitude to other components of the waveform.
Describe the general function of a differential voltmeter.
Its general function is to compare an unknown voltage with an internal reference voltage and to indicate the difference in their values
What item of test equipment is used to indicate the frequency of an external signal?
Frequency meter.
List the parts of most heterodyne frequency meters.
A heterodyne oscillator, RF harmonic amplifier, crystal-controlled oscillator , a mixer or detector , a modulator , an AF output amplifier, and a means for indicating frequency.
Wavemeters are calibrated resonant circuits used to measure frequency. List the three basic kinds of wavemeters.
Absorption, reaction, and transmission.
Of the three basic wavemeters, which one is commonly used to measure microwave frequencies?
Transmission.
The counter frequency meter is a high-speed electronic counter, with an accurate, crystal- controlled time base. What does this combination provide?
A frequency meter that automatically counts and displays the number of events (hertz) occurring in a precise interval.
What does the Model 5245L counter frequency meter measure?
Frequency, period average, ratio of two frequencies, and total events.
By what method is dc power determined?
P = IE
You use a resistor that is specially designed to dissipate the required amount of power and replace normal loads. List the two types of resistors used for this purpose.
dummy loads
dummy antennas
List the major sources of error that affect the overall accuracy of power measurements.
mismatch error
RF losses
instrumentation error
The Huntron Trackers 1000 and 2000 are for use on circuit boards and systems with all voltage sources in what condition?
in the power off condition
What mode on the automatic transistor analyzer Model 900 has the SonalertTM?
the SND mode
What type signal display does the Huntron
Trackers 1000 and 2000 show when the signal fuse is open and the test leads shorted together?
displays short circuit signatures, even with the test leads open
When using the Huntron Tracker 2000, why must you make good contact with the test leads?
because the test leads are conductive only at the tips.
What is the minimum total shunt im- pedance across the junction of the diode or transistor under test using the automatic transistor analyzer Model 900 to ensure a good test reading?
not less than 270 ohms
What is the principal function of the signal generator?
the production of an alternating voltage of the desired frequency and amplitude
While various types of FM signal generators are available, many are restricted to special applications. What type is used for general applications?
the sweep generator
Most frequency-swept signal generators use a reactance-tube method of modulation. What is the reason for this?
it results in greater flexibility, and the equipment is light and more compact.
What is a common application for pulse- modulated generators?
checking receiver performance in radar systems that have a pulse-type emission
Signal analyzers can be used in many applications. It is used for what function?
to check the response of an equipment under simulated conditions or specific operations
What determination can you make by observing the square wave response?
whether the transmission of low or high frequencies is affected.
An oscilloscope probe reduces the loading effect of the O-scope input circuit on the circuit under test. What is the second purpose of the probe?
to reduce the amount of signal voltage applied directly to the O-scope input connection
The synchroscope is an adaption of the
oscilloscope. What is the difference of the trace on the synchroscope and oscilloscope?
a trace on the synchroscope is produced only when it is initiated by an input trigger; the O-scope has a continuous sawtooth sweep.
Describe what factors a spectrum analyzer exhibits.
a spectrum analyzer is a device for exhibiting the spectrum of modulated waves in the radio-frequency range and microwave region
Describe the purpose of the echo box.
it is used in field testing, troubleshooting and adjusting pulsed -type radar systems.
What limitation should you consider when you use the echo box?
you need to remember that the echo box presents only relative rather than absolute values of power and sensitivity and only rough values of frequency.
Describe some of the main uses for the TDR.
test sets are used to check and troubleshoot aircraft wiring, transmission lines, and antenna systems for shorts, opens, crimps, or bad couplings
Describe the basics of TDR.
begins with the insertion of a step of pulse of energy into a system of cable. then, at the point of insertion, the energy reflected is observed.
While you can determine different types of discontinuities with the TDR, what else can
you determine through proper analysis?
you can determine if the discontinuity is resistive, inductive, or capacitive and whether it is in series or parallel with the load
What factor determines the speed at which a wave travels through a transmission system?
the systems velocity constant; a wave travels through air faster than it does through polyethylene
By what method does using a TDR help you locate an unacceptable connector?
TDR rapidly shows where mismatches are located; how bad they are; if they are resistive, capacitive, or inductive; and whether in series or shunt.
While TDR and FDR provide similar measurements, the FDR eliminates what limitation of the TDR?
FDR checks cables at their actual operating frequencies, eliminating the limitation of TDR discontinuities outside the operating frequencies
Describe the means by which the FDR identifies defective systems.
the FDR identifies defective systems by injecting an RF signal into a system and using insertion loss and return loss measurements to classify the system under these as good or in need of repair.
When determining cable lengths or distance to faults, what means do you use to determine the number of feet from the cable end to the fault?
the resulting CRT display consists of a series of half-dome ripples. a count of the total number of these ripples multiplied by the calibration factor identifies the location of the fault
List the elements of a typical VAST station.
a computer subsystem, a data transfer unit, and a stimulus and measurement section that contains functional building blocks configured to meet the intended test applications
List the three levels of detection that ensure rapid confidence tests and easy fault detection.
auto-check
self-check
self-test
What is the purpose of programmed halts?
to allow manual intervention during the course of testing to make adjustments and observations.
