Noob question. How do you check a resistor?

What does it measure in ohms?

HI

.07

I set my voltmeter at the "200" mark and touched both ends of the resistor with the + - cable of my voltmeter. It read at .07

I did find a small number written on it. 15KW

thanks

It sure isn't 15 kW - maybe 15 kOhm? You need to measure it with the power cord unplugged and with an ohmmeter.

Resistors are rated for resistance (ohms) and dissipation (watts). You are only interested in the resistance figure. See:

This will tell you what it is. To find out what it should be you need either the circuit diagram or the labelling on the resistor. See:

Your example might not fit any of the standard marking schemes.

A resistor might be designed to run quite warm, or warm running might indicate a fault elsewhere in the circuit.

Dissipation is important if he is going to replace it

Cub

"Asimov" wrote in news:MSGID_1=3a167=2f133.0 snipped-for-privacy@fidonet.org:

Or; Bad Boys Rape Our Young Girls But Violet Gives Willingly.

"rutman" bravely wrote to "All" (12 May 05 04:20:22) --- on the heady topic of "Noob question. How do you check a resistor?"

ru> From: rutman ru> Xref: aeinews sci.electronics.repair:47927

ru> this is very noobie question, please accept my apologies in advance.

ru> Could someone be kind enough to tell me how to check for resistor ru> functionality?

ru> I pulled the resistor and theres no writting on it other than R10.

ru> Its an inline resistor.

ru> I think it is defective as it got overly warm.

ru> please advise.

Hi, noobie! ;-)

If the resistor let the smoke out then it was overly warm. If it still looks intact then it is likely still good. Resistance is easily measured with a dmm's ohm-meter range. I'm curious what that resistor was used for? Resistors with wire terminal don't often have writing on them, just a colour code. Surface mount types sometimes have writing.

A*s*i*m*o*v

(resistor colour code:) (black, brown, red, orange, yellow, green, blue, violet, grey, white) ( 0 1 2 3 4 5 6 7 8 9 )

(resistor colour code nmemonic:)

... Bad Beer Rots Our Young Guts But Vodka Goes Well.

Wire wound - ie high power types - usually do, though?

--

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.

Rutman-

A resistor's job is to convert electric current to heat. If it is still getting hot, it is probably still good. If it overheats, the problem is more likely something else that causes too much current to flow through the resistor.

From your description, my "wild" guess is that it is a wire-wound power resistor, possibly encased in ceramic. It might have a resistance of 0.1 Ohm (from the R10) and a power rating of 15 Watts.

However I suspect you may have misread your voltmeter, as 0.07 voltage drop is not likely to be enough to make it hot. If it was actually 0.7 volts and the resistor was 0.1 Ohm, 7 Amperes would be flowing and it would be burning 4.9 Watts. This would be within the 15 watt rating but it would probably be too hot to touch. (If you Google for "Ohms Law" you can check my calculations.)

Getting back to reality, you need to provide us a little more information for a better answer. What kind of equipment is the resistor installed in? You say it is an inline resistor. What is it in line with?

Does your voltmeter have other functions? If it has a resistance range, it can check some resistors. However you must not connect it to a "live" circuit or you will burn out the meter! If my guess is right about this one's resistance, the meter may not be able to read it since the meter's test leads could have more resistance than the resistor being measured.

Fred

"Jim Yanik" bravely wrote to "All" (12 May 05 14:40:41) --- on the heady topic of "Re: Noob question. How do you check a resistor?"

JY> From: Jim Yanik JY> Xref: aeinews sci.electronics.repair:47975

JY> "Asimov" wrote in JY> news:MSGID_1=3d3a167=3d2f133.0 snipped-for-privacy@fidonet.org:

JY> Or; JY> Bad Boys Rape Our Young Girls But Violet Gives Willingly.

Jim,

But you would be accused of being sexist in our modern PC days. ;-)

A*s*i*m*o*v

... From small chips to big breasts, silicone is great!

"Dave Plowman (News)" bravely wrote to "All" (12 May 05 16:15:51) --- on the heady topic of "Re: Noob question. How do you check a resistor?"

DP(> From: "Dave Plowman (News)" DP(> Xref: aeinews sci.electronics.repair:47980

DP(> In article , DP(> Asimov wrote: > Resistors with wire terminal don't often have writing on > them, just a colour code.

DP(> Wire wound - ie high power types - usually do, though?

Oh, the ceramic rectangles, right, was forgetting those. In fact it is striking a bell in that op did mention 15KW. That's some big resistor though even if it measures only R07!

A*s*i*m*o*v

... Resistance Is Futile! (If < 1 ohm)

He is not interested in measuring the dissipation. If he needs to replace the resistor he needs to consider the dissipation of the replacement, as well as other factors. He can face that issue when (if) the time comes.

He mentioned it being marked R10. In the UK, this would suggest it was an

Are there no color bands on it? If it got too warm you'll have to find the shorted part that caused it to get too warm in the first place or a new one will do the same thing.