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Simpson 260 problems.

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Patrick

Sun Feb 12 2012, 03:22AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

when you said "it pegs" on current measurments, you mena tit went fulll scale right? the needle did move right?

sbs_2010

Sun Feb 12 2012, 03:33AM

Registered Member #4392 Joined: Mon Feb 06 2012, 01:04AM
Location: Duffield, Va
Posts: 10

Patrick wrote ...

when you said "it pegs" on current measurments, you mena tit went fulll scale right? the needle did move right?

Yeah, it did at first, when i had it in series with the red led. But, connected how i had it in my last post, it read 17 microamps and wouldnt change no matter what scale. Which, according to ohms law, is right. It just doesnt change when i change ranges. The movement is fine, as it measures volts correctly, as compared to my other meter.

Sulaiman

Sun Feb 12 2012, 06:59AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Just checking,
you are using COM and POS terminals right?

sbs_2010

Sun Feb 12 2012, 01:04PM

Registered Member #4392 Joined: Mon Feb 06 2012, 01:04AM
Location: Duffield, Va
Posts: 10

Sulaiman wrote ...

Just checking,
you are using COM and POS terminals right?

Yes, except for one time I connected it to com and 50uA it read 17uA, which was correct. When connected com and POS, it still reads 17 on the scale, on 500mA, 100mA, 10mA and 1mA ranges.

Wolfram

Sun Feb 12 2012, 02:19PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Patrick wrote ...

Sulaiman wrote ...

I agree with Steve, something in the current-shunt chain is open circuit,
most likely a resistor.
Using low voltage and a high resistance,
(e.g. 9Vdc, 1MOhm)
increase the current range until the meter reading drops
then you will know where the open circuit is.
(the resistor for the previous range) .

if there blown, then they're closed circuit--short, not open.

No, this is wrong. If a current meter is more sensitive than it should be, the shunt resistor can't be shorted. Please check your information more carefully before posting to avoid misleading others.

Here's a manual for your merer

, there's a schematic on the last page. Check resistors R12-R15 and the wiring around them. The problem could also be caused by dirty switch contacts in the mode selector.

Conundrum

Sun Feb 12 2012, 02:31PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

I had this happen on a cheap DMM, problem was an open shunt resistor on one of the ranges.

-A

sbs_2010

Sun Feb 12 2012, 02:45PM

Registered Member #4392 Joined: Mon Feb 06 2012, 01:04AM
Location: Duffield, Va
Posts: 10

Ill check those resistors this evening when I get off of work. If I cant figure it out, ill post a video on YouTube and put a link here so you all can visualize whats going on

Patrick

Sun Feb 12 2012, 02:53PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Wolfram wrote ...

Patrick wrote ...

if there blown, then they're closed circuit--short, not open.

No, this is wrong. If a current meter is more sensitive than it should be, the shunt resistor can't be shorted. Please check your information more carefully before posting to avoid misleading others.

oops i thought it was the other way around, students most often killed the 260 when making current measurements. I remember that from my first EE classes.

sbs_2010

Tue Feb 14 2012, 03:28PM

Registered Member #4392 Joined: Mon Feb 06 2012, 01:04AM
Location: Duffield, Va
Posts: 10

Well, some resistors don't measure correctly. I think i may just change some resistors and see if it helps. This is really bugging me. I tried cleaning the switch conacts with alcohol too, and it didn't change anything, so I think the contacts are fine.

Patrick

Tue Feb 14 2012, 04:59PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

sbs_2010 wrote ...

Well, some resistors don't measure correctly. I think i may just change some resistors and see if it helps. This is really bugging me. I tried cleaning the switch conacts with alcohol too, and it didn't change anything, so I think the contacts are fine.

I guess if they read higher in resistance, that would cuase a greater v drop, which would incrrease the sensitivity in the current measurement.

you can get precision resistors in many values... if you really want an anaalog meter a fully functional 260 is a great one.

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