Multimeter help

[TerryW]

I got a new digital multimeter last week cuz I left my 30-year-old multimeter out in the rain.  

So, this is a Klein MM200.  My question is even WITHOUT the leads plugged in on both AC and DC the display is constantly changing volts ( negative 90 to positive 30)  and NEVER shows ZERO.  The leads are not plugged in!!!!  With the leads plugged in it does the same thing.  I'm trying to wire a 7 wire trailer plug and I don't feel I can trust this thing.  I surely can't trust it on the blinker wires....  It works fine on an AA or the truck battery but I don't need to measure any known voltages. 

Any ideas other than trash it?

[TGO David]

What happens when the leads are plugged in?  A good auto-ranging meter shouldn't behave this way but most of those have a small choke (several micro-Henrys) across the input terminals to prevent it from happening.  I'd return it to the store just to be safe and see if another of the same model does the same thing.

 

[TGO David]

What happens when the leads are plugged in?  A good auto-ranging meter shouldn't behave this way but most of those have a small choke (several micro-Henrys) across the input terminals to prevent the input terminals from acting as antennae without a load present.  If it acts this way with the leads hooked up, I'd return it to the store just to be safe and see if another of the same model does the same thing.

 

[TerryW]

David It does the same thing with or without leads..  I think it has got a "bug" inside.  Right now with leads in it shows -290 volts DC and climbing.  My 30-year-old cheapy worked great.  It was a sad day to throw it away. 

I think you are right,  I'll return it. 

[Dustbuster]

try opening it up and shaking it in case theres a solder ball or trash inside, also check the battery or change it. if all else fails harbor freight has a handful of dmm under 20 bucks thatll get u thru.


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[gomer pyle]

Sounds similar to the Greenlee's that work bought. They are considered "smart meters".  I have seen them show voltage where none existed and visversa. I never trusted them. Does it self change between AC and DC? I would try to return it, you will never full trust it even if it starts acting right.

 

[TerryW]

5 minutes ago, gomer pyle said:

 Does it self change between AC and DC? 

 

1

Yes it does...  I'll return it.  

 

In the mean time, I do have a Sperry clamp meter that I think requires a bachelor degree to use but I'll figure it out enough to get through the job. 

[TGO David]

Quote

Sounds similar to the Greenlee's that work bought. They are considered "smart meters".  I have seen them show voltage where none existed and visversa. I never trusted them. Does it self change between AC and DC? I would try to return it, you will never full trust it even if it starts acting right.

 

 

28 minutes ago, TerryW said:

Yes it does...  I'll return it.  

 

In the mean time, I do have a Sperry clamp meter that I think requires a bachelor degree to use but I'll figure it out enough to get through the job. 

 

If you live near a source of Amplitude Modulated (AM) broadcasting, you may very well be picking up signal.  I've seen this happen before with DMMs that had very sensitive inputs.

[Alleycat72]

Are you sure it's not micro volts?

[mikegideon]

Short the leads together and see what it reads. If the meter is reading 290 volts without the leads connected, it's broken.

I have used cheap mulitimeters in real heavy AM RF fields.They will pick some stuff up with open leads, but are normally fine once the are connected to a circuit. I'm talking about using them at the transmitter site, where fields are 10 volts per meter and above.

 

[peejman]

2 minutes ago, alleycat72 said:

Are you sure it's not micro volts?

That's what I'm thinking. It's a thing I find annoying with highly sensitive digital meters.  They look like they're very erratic but they're just picking up noise.  Sometimes there's an adjustment for the cut off. 

[Alleycat72]

I see it all the time in my equipment.  

[TerryW]

Ohhhhh it is micro volts.  I see an "M" on the display.  Should it pick up noise with no leads? 

 

 

[mikegideon]

Just now, peejman said:

That's what I'm thinking. It's a thing I find annoying with highly sensitive digital meters.  They look like they're very erratic but they're just picking up noise.  Sometimes there's an adjustment for the cut off. 

If it's an auto ranging meter, 290 microvolts could be a normal stray AC voltage. Digital multimeters have high input impedances, usually around 10 megohms.

 

[mikegideon]

Just now, TerryW said:

Ohhhhh it is micro volts.  I see an "M" on the display.  Should it pick up noise with no leads? 

 

 

YES IT SHOULD. Short the leads together and it should drop to zero (ish).

[TerryW]

Just shorted it and it reads zero.. 

It is noise.. I don't think I'm near an AM station but I don't know for sure.

[TerryW]

Dang!  Thanks you guys!!!  

[Alleycat72]

There's static electricity in the atmosphere it's reading. That's what I'm going with this week. LOL 

[TerryW]

I admit I cursed the Chinese for making an inferior piece of equipment...

 Now I gotta send out 1.3 billion apologies. Do you think they all have email? 

[TGO David]

7 minutes ago, TerryW said:

I admit I cursed the Chinese for making an inferior piece of equipment...

 Now I gotta send out 1.3 billion apologies. Do you think they all have email? 

Just email it to "dissident@mail.gov.cn" and I am sure they will see it.  

 

[NextExit]

1 hour ago, alleycat72 said:

There's static electricity in the atmosphere it's reading. That's what I'm going with this week. LOL 

Or he's got a ham radio op nearby that's keying up his old Hallicrafters 

[R_Bert]

I whacked mine on the table top, and it is fine now.

[1fast4by]

Ive had the same Fluke 87 for 15 years now... If I had to purchase one all over again, Id buy a Fluke 87.

[quietguy]

1 hour ago, 1fast4by said:

Ive had the same Fluke 87 for 15 years now... If I had to purchase one all over again, Id buy a Fluke 87.

The 87-III and 87-V are the meters to have.  I have 189, and it has been nothing but a headache.  

[mikegideon]

8 hours ago, quietguy said:

I have 189, and it has been nothing but a headache.  

Same here.