# Tagged Questions

Single universal measurement device that can be used to measure voltage [V] and current [A] in both AC and DC, as well as resistance [Ω]. Often many other ranges are available like frequency [Hz], duty cycle [%], capacity [F], ... Most are hand held, some more expensive ones come as a bench model.

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### Why does a voltmeter show voltage drop

Consider this circuit. What would I get if I measure over R1? It should be less than 12v, right? But then what volatage is LAMP1 running at? Is it still 12v, or is it the voltage I measured across ...
131 views

### Why does a voltmeter read lower across a load than across a supply?

From the Wikipedia article about series and parallel circuits: As an example, consider a very simple circuit consisting of four light bulbs and one 6 V battery. If a wire joins the battery to one ...
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### Current measurement maximum time

On my multimeter I have two current measurement connection. One for the mA and one for the A. On the ampere one there's a time limitation but not on the mA one. Also they mention in the manual a kind ...
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### Measuring Voltage and Curent Simultaneously with Probe?

I have very little experience with electricity, but I am doing a project in which I need to measure power output of solar cells. I am currently using this: ...
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### Multimeter resistance measure

I've found this question but they don't talk about damage (Multimeter ranges) If I measure a 20KOhm resistance an I'm for example in the 200Ohm range, can this damage my multimeter ?
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### Measuring current drawn on a 12V barrel plug

I would like to replace my monitor power supply it's 12V 3A and I doubt it's actually necessary -- old LCDs were pulling that current and this is not CCFL but LED. So I would like to measure the ...
3k views

### Is it worth really buying a Fluke for hobbyist use?

Well, the question is the title: Is it worth really buying a Fluke for hobbyist use? I have a cheap meter at the moment. Is it worth spending a 3 figure sum on a nice, shiny, new Fluke? I honestly ...
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### Why does a multimeter put more voltage to measure a smaller resistance?

I noticed this behaviour on two different multimeters (different models and brands as well). At first I did not put a multimeter in the way to measure how much voltage changed for the different scales ...
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### How to measure current with multimeter

I want to measure both voltage and current from an output expansion port, of the BeagleBoard-xM. I managed to measure voltage by putting measuring lead (red) to the expansion port and reference lead ...
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### Accuracy when measuring current (mAmps) and small voltages

I'm looking at a circuit (part of a bigger circuit) that consist of a 10 ohm resistor and a red LED. It's running on 2.05V (checked with 2 different multimeters, ranging from from 2.047V to 2.05V). ...
310 views

### Why isn't ammeter protected with a fuse

Why is it that the ammeter with low current (200mA) limit are fused and not the 20A one? I recently lost a multimeter because i connected the ammeter in parallel by mistake. Edit: All the ammeters i ...
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### Tried to measure current with red lead in voltage socket - bad for multimeter?

I just tried to measure the current that my circuit draws when powered by 2xAAA batteries (3 V) using my Fluke 87-V. I connected the leads in series with the battery, but I accidentally left the red ...
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### Clarify multimeter current reading range?

I'm a bit confused about the range on my multimeter. I have connected the multimeter to a 5V USB wall charger rated at 1.3A. When I'm measuring voltage, everything makes sense. It shows a 1 for 200m ...
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### Measuring the frequency of a 0-5V signal with DMM and no oscilloscope?

I'm trying to determine whether I can use a DMM to monitor a 0-5V signal of a cam and crank sensor. Both are magnetic. I have a 5V ref. The sensors should vary between 0V and 5V with a short pause ...
191 views

### Detect electrical signals from plants

My daughter wants to do a science fair experiment that involves reading the electrical signals in plants, but the cost of a multi voltmeter with data logging is very high. Can anyone suggest a setup ...
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### Searching for a desktop power supply and multimeter [closed]

I was hoping to start off with a cheap,safe, working desktop power supply that can deliver enough power for me to tinker with small electronics projects (no more than a few volts and very low ...
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### What does it mean that a multimeter is four and a half digit?

The fluke 87-V is advertised as a "four and a half digit" meter. What does that mean, how does half a digit fit into the equation?
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I have a cheap multimeter that used to work fine but now it has negative readings -- even when the leads aren't connected. I changed the battery, looked for a blown fuse but no luck. Any idea what's ...
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### Using a DMM to measure output isolation/crosstalk

I'm making some PCB's that have some DC to DC converters on them with three 5 Volt converters, one 15 volt converter, and a converter with +/- 12 volts DC. On the PCB the output pins are in a ...
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### Why does a multimeter in resistance mode show initial continuity over a diode?

I originally phrased this question very differently; the original text is retained below in case background information is useful to clarify the context. When I using this digital multimeter to ...
2k views

I just got my first multimeter and when I measured a 12V 1.2ah lead-acid battery I get AC 28.8V and DC 13.4V. Is this normal? In addition I tested an AA 1.5V battery and I got 2.9V (AC setting 200) ...
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### How to interpret diode-mode readings from a multimeter

I'm using this multimeter to examine a heat gun fan. The fan has four contacts placed in a circle (well in a square inside a circle). Two opposite each other are labeled ...
1k views

### Why does a multimeter show VAC on VDC power supply output?

I used my simple digital multimeter to measure the real output of several small PSU's I have got at home. They all should give just direct current and show some values in VDC mode, but the multimeter ...
170 views

### What do I need to know about leakage current?

I recently suggested a plan of removing one end of a resistor from a breadboard to remove it from the circuit in order to measure its resistance, but my mentor suggested that this won't work for high ...
170 views

### How can I test my multimeter's battery without a low battery indicator?

I a few months ago needed a multimeter, and I didn't have one. Not wanting to wait for one to arrive, and only needing it once, I went out to the hardware store and bought a cheap digital multimeter. ...
145 views

### How do I figure out the correct polarity of a DC barrel connector

I'm in the U.S. and I bought a digital wall clock from the U.K. which came with an AC adapter with input 230V/50Hz/90mA and output 9V/800mA. Now I could get a transformer to convert 120V to 230V but ...
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### If I set a multimeter on 'ohms' and put it across a battery, does it short the battery?

As the title says. I am not very good at electronics (I might have, uh, actually done this, for no good reason...). I am wondering now if I should be worried about the battery being damaged.
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### Correct negative current measurement but incorrect positive measurement

I'm trying to replicate a simple circuit that I designed in SpiceIV. Here's what it looks like I should be getting ~23 mA of current flowing through this circuit by ohm's law. However, when I ...
234 views

### Why might a multimeter ask for “wrong” fuse sizes?

Why might a multimeter ask for the "wrong" sizes of fuses? On the front of my Fluke 87 multimeter, the two probe ports for amperage are labeled as fused at 10A (max) and 400mA (max). When opening the ...
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### Can current still be (alternatively) measured with a blown multimeter fuse?

With a blown fuse in a multimeter, is it still possible to measure current of a device by somehow measuring voltage and resistance? If so, how would this work? Do specific probing/measuring points ...
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### Why does my multimeter use increments of 2?

I bought a cheap multimeter (etek 10709 if you are curious) from Walmart the other day to just check out a few readings on my cars ignition system. While I have no problem getting the reading (in ...
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### Continuity test buzzer sounding continuously

I have a digital multimeter (DT 9205) which went on the blink recently. I was using the continuity function to check a circuit. With the wisdom of hindsight, I think it is possible that the cicuit ...
550 views

### General PSpice and 555 timer question regarding precision

I have been experimenting with values recorded using a multimeter versus the voltages (RMS) simulated using capture. I simultaneously setup a circuit using a breadboard and drew exactly the same ...
356 views

### What color is positive on a multimeter?

I bought a multimeter with attached leads. I would think red is positive but when I take a reading it only works if I use black as positive. Was it assembled wrong? There's nothing in the manual. It's ...
175 views

### Measuring small Off state leakage current 10uA or less

I have a solid state relay an AQZ207 to be exact. I want to be able to measure the off state leakage current of the FET which in the datasheet seems to around 10uA Max. I had some ideas, but not sure ...
467 views

### Why one of my multimeter shows a small voltage when only one probe is connected to AC and the other dont?

I've recently acquired a Minipa ET-997 multimeter. I noticed that when I connected one probe to 127V phase and let the other disconnected, it will show around 12V. But I have an older and cheaper ...
309 views

### What's the low voltage displayed by a voltmeter when only one of its probes is connected?

Recently I was toying with a digital multimeter and observed the following. The multimeter was set to measuring AC voltage with the upper limit of 750 volts. It has two probes which I will call "red" ...
583 views

### What to look for in a multimeter?

When selecting a multimeter, what should one look for in terms of safety features and measurement capabilities? What can you look for in the specifications to tell a good meter from a crappy one ...
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### why is wall voltage measuring 175V?

I was trying to use a DM-4100A multimeter to verify a power supply, and I'm not sure I'm using the multimeter correctly. The multimeter is >10 years old too, so maybe it is not working correctly. ...
1k views

### How to determine the units when reading a multimeter?

Say for instance I am trying to measure the current. The units around the edge of the multimeter is 2000u, 200m, 20m, 10A, etc. Does this mean that the reading displayed on the multimeter is in that ...
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### Digital multimeters battery placement

Apologies if this is a ridiculous question. I'm completely new at electronics, and so I just got my first multimeter - a pretty cheap one, a Draper Digital multimeter. Got my first problem with it as ...
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### How does a multimeter convert voltage/current to a numerical value?

Just wondering... How does a digital multimeter work ? How can it convert a voltage, a current or a resistance to a numerical value ? I guess there is some programmable chip inside, but how does this ...
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### range switching problem in auto range multimeter using PIC microcontroller

I am designing a auto range multimeter with PIC microcontroller and added extra circuitry for attenuating the signal uu to 3.3V for ADC of PIC controller. The problem I am having is in the auto range ...
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This is a sensor arm of a hard disk containing a GMR or TMR magnetic sensor and a coil for creating the write field (1-3 GHz at around 2 Tesla as far as I know). I'm counting 6 conduction lines, ...
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### Can I burn components / short circuit by using a multimeter

It's probably not new to you, but sometimes we want to analyze a powered circuit with a multimeter. I love to do that, but I'm a little worried that I might burn some components or the whole circuit. ...
747 views

### What tests for a defective IC may be done with only a multimeter?

Linked to an earlier post How do I test a circuit without an oscilloscope? Background : Inching forward from the previous post I started to do a simple 555 astable with super super long duration ...
554 views

### What is the easiest way to connect a breadboard to a multimeter?

The test leads on my multimeter are too large to fit in the holes in my breadboard. How can I easily connect my multimeter to test voltage on my breadboard?
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### What is the best way to switch between different ranges when designing a multimeter using microcontroller?

We are developing a multimeter using a PIC18 microcontroller and we are searching for the best method to switch between different ranges in multimeter with the smallest possible amount of switching ...