1% Resistors huh?

[Sig239]

I guess I just assumed they meant it. What is supposed to be a 6.8K is actually 6490hm:- 4.8%. Some of the others I checked were almost as bad. Is this normal or did I get a bad batch? They came with my inchworm kit and they are used in a voltage divider. Should I go ahead and use them, or do I need to go out and get more.

 

[evandude]

A natural first question would be - how good is your multimeter?

 

[Sig239]

I guess it's OK. It's not a fancy high dollar fluke or anything, but it hasn't let me down yet. Checking the same resistor always yields the same results so I guess it's consistant. It doesn't always read low, some of the others read high. I bought it at the Shack RS# 22-816, True RMS. EXTECH instruments made in china?!?!?!

EDIT: The voltage measurements are good according to my scope.

 

[dknguyen]

Precision/Consistency != Accurate

If you are so worried, just match the resistors up before sticking them into the divider.

 

[Sig239]

Precision/Consistency != Accurate

If you are so worried, just match the resistors up before sticking them into the divider.

I know that doesn't make it accurate, I just don't have any other reason to believe it isn't. Match it up? I don't have any others of those values. Both 6.8k read low (by different amounts) and both 2.2k read high (also by different consistant amounts). So as I posted, is it normal for 1% resistors to be off by up to 4 or so percent? Apparently not, judging by the responses. Thank you for responding.

 

[justDIY]

doesn't sound normal to me, I've never measured even a 5% resistor that's off by more than 1-2% at room temperature. I think the 5% means the value will change no more than + / - 5% over the entire rated temperature range, so it -20 degress it might be 4% lower and at 150 degrees it might be 3% higher?

I will try measuring some of my 1% resistors sometime this weekend and see what they say - I've got a couple cheapy dmms and one expensive benchtop one.

 

[Sig239]

Hello justDIY thanks for the response

After the previous posts I was wondering about the accuracy of my DMM so I got out the other 1% resistors (not the ones I need of course) and they were all well within the 1% range. Even the 47 ohm resistors were reading like 47.2, so that is leading me to believe that I got some out of spec resistors.

BTW the resistors I aready had, and the ones that came with the kit are the 5 band type and the last two bands are brown. According to what I've read the 4th band represents the tolerance (brown=1%) and the 5th band represents the percentage of resistance change per 1000hrs of operation (brown=1%). And before you ask, No there was NOT solder on the leads when I got them

 

[Sceadwian]

What's the manual for your meter say? It's going to give you a percent full scale error and non linearity percentage for each of the ranges. Keep in mind the resistors inside the meter itself are usually only 1% themselves. If you need to fine tune a resistor divider network to that extreme anyways you're going to want to use a trimmer pot.

 

[Sig239]

What's the manual for your meter say? If you need to fine tune a resistor divider network to that extreme anyways you're going to want to use a trimmer pot.

I didn't design the circuit, so I don't know to what extreme was intended, but I assume if they specify 1% components then that is the extreme. Even with the specs. of the meter the resistor is off by at least 200% of the advertised accuracy. I suspect however that the meter is not that far off and the supplied resistors are even further out of spec. Is it really that hard to believe ? Anyways the designer has responded in another thread that the resistors I have will indeed work, so I guess it did not need to be quite that precise.

 

[Sceadwian]

1% isn't really precise, It's just a lot more accurate that ultra cheap 5% parts. Usually a design will outright call for calibration of a resistor if it's that important, or use a trimmer. Just tacking on a trimmer resistor is a whole lot more practical and less expensive compared to going to a laser trimmed resistor.

 

[Hero999]

Are they areactually 1% tolerance resistors?

Just because the manual says they are it doesn't mean it's true, check the tolerance band to see if it's brown.

All the resistors I've measured are better than the tolerance value, most manufacturers have a quality control system like six sigma to ensure the tolerance of their components.

 

[Sceadwian]

Right now all I have are 1% resistors, they're only 1/4 watt though.

 

[Sig239]

Manual for what? As far as I'm concerned the meter is not in question. 50 resistors very well in spec. and 4 very far out of spec. The 50 I already had, the four came together with a kit. See the connection? The 4th and 5th bands are brown.

 

[Sig239]

Right now all I have are 1% resistors, they're only 1/4 watt though.

That's what I have.

 

[Hero999]

The manual for the kit.

Resistors are so cheap anyway, it isn't that hard to buy some new ones if you're worried because your application requires accurate components

 

[eng1]

BTW the resistors I aready had, and the ones that came with the kit are the 5 band type and the last two bands are brown. According to what I've read the 4th band represents the tolerance (brown=1%) and the 5th band represents the percentage of resistance change per 1000hrs of operation (brown=1%).

I've read about this code, but it does not apply to my 1% resistors. The 5th band is the tolerance! and it brown, as expected. Read this code:
grey-blue-blue-red-brown
What's the resistance?

 

[Sig239]

After surfing around I see that you are right about the color bands. I suppose it to be an error in the book I have. HMMM

 

[eng1]

After surfing around I see that you are right about the color bands. I suppose it to be an error in the book I have. HMMM

**broken link removed**