multimeter troubleshooting open and short s and grounds and resistors circuits pdf

Multimeter Troubleshooting Open And Short S And Grounds And Resistors Circuits Pdf

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But wait - what is a multimeter and how does it work? Want to get straight to troubleshooting? No worries, click here for our easy steps on how to use a multimeter for troubleshooting your sensor!

How To Find a Short Circuit with a Multimeter

This Application Note compiles solutions to current sensing problems and organizes the solutions by general application type. These circuits have been culled from a variety of Linear Technology documents.

Each chapter collects together applications that tend to solve a similar general problem, such as high side current sensing, or negative supply sensing. The chapters are titled accordingly. In this way, the reader has access to many possible solutions to a particular problem in one place.

It is unlikely that any particular circuit shown will exactly meet the requirements for a specific design, but the suggestion of many circuit techniques and devices should prove useful. To avoid duplication, circuits relevant to multiple chapters may appear in one location. This chapter introduces the basic techniques used for sensing current. It serves also as a definition of common terms. Each technique has advantages and disadvantages and these are described. The types of amplifiers used to implement the circuits are provided.

Current sensed in the ground return path of the power connection to the monitored load. Current generally flows in just one direction unidirectional.

Any switching is performed on the load-side of monitor. Current sensed in the supply path of the power connection to the monitored load.

Bidirectional current sensed in a bridge driven load, or unidirectional high side connection with a supply side switch. This chapter discusses solutions for high side current sensing. With these circuits the total current supplied to a load is monitored in the positive power supply line. This is the basic LT circuit configuration. The internal circuitry, including an output buffer, typically operates from a low voltage supply, such as the 3V shown.

The A2 and A4 pins can be strapped various ways to provide a wide range of internally fixed gains. The input leads become very Hi-Z when V CC is powered down, so as not to drain batteries for example. Access to an internal signal node Pin 3 provides an option to include a filtering function with one added capacitor. Small-signal range is limited by V OL in single-supply operation.

This circuit uses generic devices to assemble a function similar to an LTC A rail-to-rail input type op amp is required since input voltages are right at the upper rail. The circuit shown here is capable of monitoring up to 44V applications. Besides the complication of extra parts, the V OS performance of op amps at the supply is generally not factory trimmed, thus less accurate than other solutions.

The finite current gain of the bipolar transistor is a small source of gain error. This provides a measure of fault protection to downstream circuitry by virtue of the limited output swing set by the low voltage supply. The disadvantage is V OS in the Over-the-Top mode is generally inferior to other modes, thus less accurate. The finite current gain of the bipolar transistor is a source of small gain error.

This circuit takes advantage of the microampere supply current and rail-to-rail input of the LT The circuit is simple because the supply draw is essentially equal to the load current developed through R A. This supply current is simply passed through R B to form an output voltage that is appropriately amplified. The LT can be used as a combination current sensor and fuse monitor. The LT inputs are tolerant of large input differentials, thus allowing the blown-fuse operating condition this would be detected by an output full-scale indication.

This is a low voltage, ultrahigh precision monitor featuring a zero-drift instrumentation amplifier IA that provides rail-to-rail inputs and outputs. Voltage gain is set by the feedback resistors.

Accuracy of this circuit is set by the quality of resistors selected by the user, small-signal range is limited by V OL in single-supply operation. This IA is sampled, so the output is discontinuous with input changes, thus only suited to very low frequency measurements. This is a configuration similar to an LT implemented with generic components. A rail-to-rail or Over-the-Top input op amp type is required for the first section.

The second section is a buffer to allow driving ADC ports, etc. As shown, this circuit can handle up to 36V operation. This particular switch can handle up to 18V, so the ultrahigh precision concept can be utilized at higher voltages than the fully integrated ICs mentioned.

This circuit simply commutates charge from the flying sense capacitor to the ground-referenced output capacitor so that under DC input conditions the single-ended output voltage is exactly the same as the differential across the sense resistor. A high precision buffer amplifier would typically follow this circuit such as an LTC The commutation rate is user set by the capacitor connected to Pin For negative supply monitoring, Pin 15 would be tied to the negative rail rather than ground.

The lower figure b is similar but derives its power supply from the APD bias line. In the single-supply configuration shown, there is also a dynamic range limitation due to V OL to consider.

The advantage of this approach is the high accuracy that is available in an IA. Figure The output current from the LTC, which is proportional to the sensed input voltage, flows through M1 to create a ground referenced output voltage.

This circuit provides the capability of monitoring current in either direction through the sense resistor. To allow negative outputs to represent charging current, V EE is connected to a small negative supply.

C3 may be used to form a filter in conjunction with the output resistance R OUT of the part. This solution offers excellent precision very low V OS and a fixed nominal gain of 8. This is the basic LTC high side sensing supply-monitor configuration, where the supply current drawn by the IC is included in the readout signal. This configuration is useful when the IC current may not be negligible in terms of overall current draw, such as in low power battery-powered applications.

Gain accuracy of this circuit is limited only by the precision of the resistors selected by the user. This is a basic high side current monitor using the LTC Thus, the amplifier can be placed directly at the shunt, while R OUT is placed near the monitoring electronics without ground drop errors.

The switch element may be the high side type connected between the sense resistor and the load, a low side type between the load and ground or an H-bridge. Current through a photodiode with a large reverse bias potential is converted to a ground referenced output voltage directly through an LTC The supply rail can be as high as 70V. Gain of the I to V conversion, the transimpedance, is set by the selection of resistor R L.

It provides the gate drive for a power switch from standard logic voltage levels. It provides shorted load protection by monitoring the current flow to through the switch. Adding an LTC to the same circuit, sharing the same current sense resistor, provides a linear voltage signal proportional to the load current for additional intelligent control. Current flow in high supply voltage rails can be monitored directly or in an isolated fashion as shown in this circuit.

The gain of the circuit and the level of output current from the LTC depends on the particular opto-isolator used. This reduces dissipation in the circuit and allows wider variations in current to be accurately measured. In this circuit, the components are scaled for a 10A measuring range, with the offset error corresponding to less than 10mA. This is effectively better than bit dynamic range with dissipation under mW.

To sense all current drawn from a battery power source which is also powering the sensing circuitry requires the proper connection of the supply pin. Connecting the supply pin to the load side of the sense resistor adds the supply current to the load current. The input voltage can extend below ground or exceed the sense amplifier supply voltage.

While the sensed current must flow in just one direction, it can be sensed above the load, high side, or below the load, low side.

Gain is programmed through resistor scaling and is set to 50 in the circuit shown. The output impedance of the LT amplifier is defined by the value of the gain setting output resistor.

Bypassing this resistor with a single capacitor provides first order filtering to smooth noisy current signals and spikes. When power is first applied to a system the load current may require some time to rise to the normal operating level. This pulse unlatches the comparators. R8 and Q2 will discharge C1 on loss of the supply to ensure that a full delay interval occurs when power returns. This can trigger and latch the LT comparator monitoring undercurrent conditions.

The power-on delay time is resistor programmable over a wide range. This chapter discusses solutions for low side current sensing. With these circuits the current flowing in the ground return or negative power supply line is monitored. This configuration is basically a standard noninverting amplifier. The op amp used must support common mode operation at the lower rail and the use of a zero-drift type as shown provides excellent precision. The output of this circuit is referenced to the lower Kelvin contact, which could be ground in a single-supply application.

Small-signal range is limited by V OL for single-supply designs. Scaling accuracy is set by the quality of the user-selected resistors. This is the same sampling architecture as used in the front end of the LTC and LTC, but sans op amp gain stage.

The commutation rate is user-set by the capacitor connected to Pin This load protecting circuit employs low side current sensing. An internal shunt regulator establishes a local operating voltage.

Electrical Short Circuit – Types, Causes and Prevention

This Application Note compiles solutions to current sensing problems and organizes the solutions by general application type. These circuits have been culled from a variety of Linear Technology documents. Each chapter collects together applications that tend to solve a similar general problem, such as high side current sensing, or negative supply sensing. The chapters are titled accordingly. In this way, the reader has access to many possible solutions to a particular problem in one place.


Diagnostic Testing and Troubleshooting. The Fluke 45 Dual Display Multimeter (also referred to as "the meter") is a Resistance between the COM binding post and the meter's internal This MOV normally acts as an open circuit​; when the S87 shorts out A1R22 both during ranging and in the measurements listed.


The basics of motor testing

A short circuit is when there is a low resistance connection between two conductors that are supplying electrical power to a circuit. This would generate an excess of voltage streaming and cause excessive flow of current in the power source. This is when a hot wire carrying current touches a neutral wire.

How to Use a Multimeter

AN-105: Current Sense Circuit Collection Making Sense of Current

Open circuit and short circuit are two special terms that represent opposite extremes of the resistance number line. Looking Into a Pair of Terminals. This means there is zero voltage difference for any current value. Note that real wires have non-zero resistance! This means that zero current can flow between the two terminals, regardless of any voltage difference. Note that very high voltages can cause arcs of current to flow even over large air or vacuum gaps!

Use an identical circuit board that you know works to determine the right voltage levels. Analyzing a circuit One should also know how to use the DVM. It is possible to damage the loop, The other possibility is that the circuit or component you are testing doesn't have continuity —that is, it has infinite resistance. So if you see reading 2 times i. In case that you are new in DIY, any multimeter will do for this, and you should use standard multimeter probes. When the capacitor is outside the board, sometime a bad capacitor may give you a proper capacitance value on the multimeter or capacitor meter.


Digital Multimeters. The metal strip is designed to melt and open the circuit if while those that limit electron flow are variable resistors. For now, we will limit In order to diagnose and repair automotive electrical problems, technicians must When diagnosing opens, shorts, and grounds, always use a wiring diagram to​.


Step 1. Check your equipment

Not sure what a multimeter is or what you can do with one? Then you're in the right place! Below is an overview of what multimeters are and what they are useful for. To learn how to use a multimeter , to find multimeter usage ideas , or to find labeled photographs of assorted multimeter models , click on the other tabs above in this multimeter tutorial. A multimeter is a handy tool that you use to measure electricity, just like you would use a ruler to measure distance, a stopwatch to measure time, or a scale to measure weight. The neat thing about a multimeter is that unlike a ruler, watch, or scale, it can measure different things — kind of like a multi-tool.

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4 comments

Paypreponra

During the worst week of my professional life, we had a shipment of overdue PCBs come in.

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Timothy F.

A short circuit can lead to deteriorating wire and cause fires. Once you've identified a potential short, use your multimeter to confirm the voltage by setting it to resistance and insert the metal probes into the problem receptacle or switch. Resources; Blog · Case Studies · Customer Stories · Datasheets.

REPLY

Before S.

Knowledge of the basics together with powerful new test equipment vastly simplifies the job.

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Moepresulna

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