Although readings of specific gravity are a reliable measure of the condition of a storage battery, cells that indicate normal may prove useless under load. This is usually caused by a high internal resistance. A load-voltage check of the cells with the use of a cell tester indicates the actual voltage charge held by each battery cell. Cell voltages should not differ by more than 0. Use extreme caution whenever testing or working around lead-acid storage batteries. Smoking and spark-producing tools or devices are also prohibited in enclosed spaces that contain lead-acid storage batteries.
When charging, these batteries produce sufficient quantities of hydrogen to produce large explosions. Lead-acid storage batteries should only be charged in well-ventilated spaces. You must periodically check dry cell batteries that are used for test instruments and portable or field equipments for loss of power. For actual voltages of dry batteries , you should measure with a battery tester for a minimum acceptable voltage before installation.
This type of tester permits you to complete a rapid and accurate measurement of battery potentials under load conditions, ranging in voltages from 1. A data chart supplied with the battery tester provides information regarding the jack to be used and minimum acceptable voltages of various batteries used in Navy equipments.
Custom Search. The ideal logic probe will have the following characteristics: Figure Be able to detect a steady logic level Be able to detect a train of logic levels Be able to detect an open circuit Be able to detect a high-speed transient pulse Have overvoltage protection Be small, light, and easy to handle Have a high input impedance to protect against circuit loading Q. The first requirement before using the logic probe is to connect the power connections to the circuit.
Apart from ensuring they are the right voltage, the points used for connecting the crocodile clips to should be accessible and provide a reliable connection without the risk of touching any adjacent components or other connections. Note: If possible connect the power connections to the unit under test when it is powered off. In this way risk of damage due to shorting, etc. It is necessary to select the required settings on the switches when starting to use a logic probe. Dependent upon the logic probe manufacturer and model, there are a number of options that may need to be set:.
Note: Some surface mount devices these days use supply rails of 3. Most logic probes will not work with these ICs as the logic levels cannot normally be accommodated. Additionally it is often difficult to probe surface mount boards as there is a real danger of shorting pins.
With power applied to the circuit under test and the logic probe, it is possible to use it to probe various points on the circuit. One easy point to locate may be a transistor driver. The can of the transistor is often connected to its collector making a point where the signal can be easily accessed.
It is then a matter of interpreting the results in line with the circuit to find out whether they are acting correctly or not.
One hint is that it is often good to check how to use the logic probe on a known good circuit. In this way you will better understand its operation and know what to look for. However it is not nearly as flexible as an oscilloscope or a logic analyzer.
A logic probe can be used for quick testing, whereas for more in-depth testing more sophisticated test equipment is needed. It should be remembered that it is not suitable for many high speed logic circuits. It typically will only be useful for basic tests on basic circuits. While all models of logic probe will vary slightly, it is possible to provide some outline of the typical specifications for a probe.
Generally logic probes are aimed at a basic test only and therefore offer a relatively basic level of performance. Nevertheless they can be invaluable in locating faults in many situations. The specifications will vary from one logic probe tester to the next, but they give the rough ideal of the performance that might be expected.
The logic probe can be a very useful simple tester and save the cost of more expensive forms of electronic test equipment having to be bought. If thier limitations are understood, then they can prove to be very useful in many instances with simple electronic circuits. What is a logic probe? The logic probe will indicate this typically with an LED which is often coloured red.
Logic low: The logic probe also is able to indicate a logic or digital low. A common indication is with the use of a green coloured LED. Digital pulses: The logic probe may incorporate some form of pulse detection circuitry.
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