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When a multimeter is set to measure resistance what reading would you expect when the probes aren't touching?
Wiki User
∙ 13y ago
If the test leads are not in contact with anything, the needle or pointer of an analog meter will be resting at the left most position. This is represents an infinite amount of resistance, or an "open circuit"; it is also safe to say there is the no continuity, or path between the black and red probes.
Wiki User
∙ 13y ago
Wiki User
∙ 14y agoWhen set to measure resistance, a voltage potential is set across the input of the meter (internally). The meter then reads the current flow caused by placing this into a circuit. The thevinin resistance is equivalent to the injected voltage / the induced current.
A: it does not read current but rather the voltage caused by this current flow trough the resistance. Even an amps meter reads voltage across a low resistance shunt
Wiki User
∙ 13y agoSomething very close to zero. Only a superconductor will read zero resistance.
ANSWER: Actually that is the first step to use when reading resistance to certify that the meter is indeed is calibrated since it will read zero. The reading will change due to the internal battery degradation with time by adjusting to zero reading that guarantee to a correct reading of resistance
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How is it possible to test a diode with a multimeter?
The diode must be isolated from any parallel current paths to test. check resistance both directions through diode. readings should show an open (or very high resistance) one direction and a short (or very low resistance) the other direction. Usually, a failed diode will show an open both directions. Set the multimeter to check resistance, attach each meter lead to opposite leads on diode, note reading, then swap meter leads and compare readings.
Why is harder to measure amperage than voltage whit a digital multimeter?
A: It harder for the simple fact that the shunt resistance must be very small and precise to give a corrupt reading. As amps increases problems crap up like the very small shunt value not forgetting then now power dissipation comes to trouble us with thermal inaccuracy due to heat
Why must power be turned off when measuring the resistance of a circuit?
If an external Voltage is applied to a multimeter while the multimeter`s function switch is in the Ohm meter position then the Ohmmeter is apt to be destroyed or disabled. Therefore the simplest answer is that the power must be turned off in order to avoid damage to the Ohm meter and possibly to yourself caused by Voltages present in the circuit while the power is own. Another reason of course is because a valid Ohm reading can not be obtained while Voltages are present across the resistance that is being measured because the Ohmmeter itself applies a Voltage across the resistance and then a sampling of the current through the unknown resistance is used by the Ohmmeter`s circuitry to cause a calibrated deflection of the Ohmmeter and thus display on the meter`s dial the Ohmic value of the unknown resistance. For the same reasons as above it is also a good practice to discharge all the capacitors in the circuit after the power is turned off and before any in circuit resistance measurements are made.
How do you know electrical is grounded?
I test it with a digital multimeter. Set it to measure the voltage you're expecting, verify that the circuit is powered (put the red probe to the positive side of the circuit, and find a different ground), then move the black probe to the intended ground. You should be reading the voltage you're expecting if the ground is good.
When using a multimeter to measure a dc current are the terminals polarity conscious?
Yes, if they are reversed the reading is also reversed. On a digital meter this will usually be displayed as a negative value, but on the older style mechanical analog multimeters it may actually damage the meter by "pegging" the needle in the backwards direction and bending it causing all future readings to be wrong.
How do you determine the anode and a cathode of a diode by multimeter?
A: ascertain the polarity of the ohmmeter leads as + - potential available then set the scale to kilo ohms and see if the reading is hi [ is the + lead is + then that imply that the diode is + to the cathode] therefore is not conducting. reverse the diode and the reading should be low implying anode is positive and the diode is conducting
Why does a multimeter display a reading of zero when both of its probes are touched to the same end of a battery?
A multimeter? Zero because there is no voltage difference, zero because there's no current flow (amperage) and zero ohms of resistance because they are both touching the same metal terminal. Or, perhaps it reads zero because you have it turned off.
How do you measure a resistor using multimeter?
a multimeter probably has a Ohm meter as well. If yes, use it and make sure you have the correct scale adjusted. If there is no Ohm meter you should calculate the resistance using Ohms Law. So if you use your multimeter as an Amp meter (in series with the unknown resistor) and you apply a know voltage across you should be able to calculate the resistance by dividing the voltage you applied by the current you meassured (R=v/I) ANSWER: 1 make sure ther is no external power connected 2 short the leads together and adjust for zero reading on the meter. This step is necessary to eliminate the internal battery drifting with time. Unlike voltage and amps reading the scaling of the meter is not important to begin with since a peg meter or a overflow will not destroy the meter immediately but do change the scale to get maximum deflection or digital display.That it
What is the resistance of a blown fuse?
Infinite...a blown fuse is an 'open' in electronics terms. Infinite resistance.It will not read zero on a digital multimeter, it will read as a maximum resistance.A fuse, when good, has zero (practically speaking) resistance. When it blows, it has infinite resistance, thus on a multimeter it will provide a high reading.... When an analogue (not digital) multi-meter is set to ohms it will read zero when blown. If you touch both leads off the meter it will read full scale. if the leads are NOT touching the meter will read zero. so if your fuse is blown it will act like the leads are not touching because it is blown. It is good practice not to touch the exposed lead ends or the fuse under test as the resistance of your body can give a false reading.The ohm scale on an analog multimeter is reversed...when the meter is at the far left, what you might think is zero, it is indicating infinite resistance. When you try and determine the resistance of a fuse that is blown, the meter will not move from the left side of the scale. That is not zero resistance. That is infinite resistance.
Multimeter measure current in amps volts or watts?
A multimeter measures current in amperes and potential difference in volts. Wattmeters are used to measure watts and the reading is a combination of current being drawn and the voltage applied. watt = volts x amps
When a multimeter is set to measure resistance what reading would you expect when the probes are touching?
Hold the probes at the end of the test leads together. The meter pointer should move fully to the right. Locate the "Zero Adjust" knob and rotate so that the the meter indicates "0" (or as close to "0" as possible). Note that this position is the "short circuit" or "zero ohms" indication for this R x 1 range of this meter. Always remember to "zero" the meter immediately after changing resistance ranges.
What are the types of multi tester?
A Multimeter is an electronic instrument, every electronic technician and engineer’s widely used piece of test equipment. A multimeter is mainly used to measure the three basic electrical characteristics of voltage, current, and resistance. There are two types of multimeters: Analog Multimeter: The Analog Multimeter or VOM (Volt-Ohm-Milliammeter) is constructed using a moving coil meter and a pointer to indicate the reading on the scale. Digital Multimeter: We mostly used a multimeter is a digital multimeter (DMM). The DMM performs all functions from AC to DC other than analog. It has two probes positive and negative indicated with black and red color as shown in the figure. there are some best multimeters for HVAC.
When the leads of the meter are touched together a nd the meter is set to measure resistance what should the resistance reading be?
Zero ohms.
What is the effect caused by ammeter resistance when an ammeter is inserted into a circuit to measure the current?
The effect the multimeter might have on the circuit when inserted to measure the current is to increase the circuit resistance and decrease the available voltage to the circuit. This is because the multimeter in amps or milliamps mode does have a small resistance which is not zero, so by Ohm's law, there is a voltage drop across the multimeter; small, but not zero. Usually this effect is small. One way to compensate is to start by measuring voltage, and then inserting a separate ammeter and adjusting the power supply to match the original voltage. Of course, the voltmeter must be downstream of the ammeter.
To measure DC of big bus bar?
A: TO measure the current on any path you will need a very small known resistance in sires and measure the voltage drop across it. If the resistance i not small then inaccuracy of reading will be evident
Why remove resister from circuit to measure resistance?
a meter uses its own supply to measure resistance. you dont have to remove the resistor from the circuit but you must isolate it from the circuit supply to get an accurate reading.
How do you measure a thyristor?
Many users of thyristors and diodes lack the proper equipment to make measurements of semiconductor parameters. The readily available battery operated multimeter is often used to try to determine the difference between acceptable and non-acceptable devices using a resistance reading. A reading of this type can lead to incorrect conclusions. MULTIMETER MEASUREMENTS The multimeter is generally used to measure the DC resistance between anode and cathode of thyristors and diodes and also the gate to cathode on thyristors. These measurements are of the "off state" or blocking voltage of the device. The only valid readings are "open circuit" and "short circuit". The anode to cathode or gate to cathode measurement must register a short circuit in both directions ( forward and reverse polarity) for the device to be declared short and infinite resistance for an open circuit. The measurement of resistance with a multimeter is an inappropriate measurement technique for separating good devices from bad. When a resistance measurement is taken with an multimeter, the internal battery voltage is typically in the range 1.5V to 15V and the leakage current of the device at this voltage will determine the measured resistance. A semiconductor has a non-linear blocking voltage/leakage current characteristic and hence a non-linear resistance curve. The blocking voltage of a thyristor is defined as the voltage at which it reaches a specified leakage current at the defined temperature. Therefore devices can have a variety of leakage current characteristics and still be within specification. PRECAUTIONS 1. Ensure that the resistance reading is only being taken across the device and not across something in parallel with it. 2. If a capsule type device is being measured, make sure that it is under sufficient load to ensure that the internal components are pressed together and high resistance readings are avoided. SUMMARY A multimeter resistance measurement is not recommended for determining acceptable semiconductor devices. As a quick check for devices in a circuit, a multimeter will allow you to determine if a device has failed catastrophically. The device with the lowest leakage current at 3V is not necessarily the one with the lowest leakage current a high voltage
