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My New Multimeter


Jeff Matthews

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OK, guys.  Electronics is not something I work on.  I got a new multimeter to test my fridge's water inlet valve solenoid.  I am testing for Ohms.  There is also a continuity test.

 

There's a plastic plug and 2 pins.  I put the leads on both pins.  No alarm sounds, and so no continuity.  The Ohm-meter shows 250 Ohms.

 

If it measured 0 Ohms, what would that mean?  That there's a closed, continuous circuit?  What's special about the number, 250 (other than it's not 0)?

 

I would like to understand what I'm doing and why.

 

Thanks.

 

 

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Testing for Ohms and continuity are pretty much the same thing.  You just want to be sure it isn't open.

 

You can't read 250 Ohms and no continuity.

 

0 ohms is a perfect circuit, I doubt you have that.  OL normally means an open circuit which is the same thing as holding the leads apart and not touching anything.

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It's a Klein MM400 auto-range multimeter.

 

I was not wanting to know how to read the meter.  I was wanting to understand the readings.  Why, for example, when I put the leads on each prong of the plug, did it read 250 Ohms?  I know V = I * R, but forgot how to apply it.  Does this mean the solenoid has a coil that requires a certain voltage/amperage combination to get through the coil's resistance?  Or what?

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You measured the coil's resistance and it is 250 ohms. If it were open, it would be bad. 250 ohms is likely good, as all coils are different based on the amount and gauge of wire in them. Look at the fridge's print to see if it shows the resistance of the coil. But as it stands, R=250 ohms, V= the voltage that operates it, and you can calculate the "I" value, current, from there.

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2 minutes ago, Davecv41 said:

You measured the coil's resistance and it is 250 ohms. If it were open, it would be bad. 250 ohms is likely good, as all coils are different based on the amount and gauge of wire in them. Look at the fridge's print to see if it shows the resistance of the coil. But as it stands, R=250 ohms, V= the voltage that operates it, and you can calculate the "I" value, current, from there.

Thanks for explaining.

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Surface mount technology and integrated circuits can make troubleshooting boards like that very difficult. I do use a multimeter regularly though on all kinds of troubleshooting efforts. A wise old electrician told me once "It has to make a circuit to do work". Keep that in mind when you use your meter.

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On 10/29/2017 at 9:07 PM, Jeff Matthews said:

the current remains the same throughout the entire circuit, and only the voltage varies across loads/resistance.  Is this correct?

Lets see now, that seems kinda right. If I have a simple circuit like a light bulb connected to a wall receptacle, voltage drops across the load (light bulb) and the current should measure the same through out the circuit.

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23 minutes ago, JL Sargent said:

Lets see now, that seems kinda right. If I have a simple circuit like a light bulb connected to a wall receptacle, voltage drops across the load (light bulb) and the current should measure the same through out the circuit.

OK.  At first glance, I thought the location of the resistor made a difference with respect to the amount of current.  Now, I see that it does not.  What about voltage?  Since there is a drop in voltage across a resistor, does that mean the location of the resistor is important?  Or can you just put the resistor anywhere in the circuit for both current and voltage regulation?

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1 minute ago, Jeff Matthews said:

Or can you just put the resistor anywhere in the circuit for both current and voltage regulation?

I believe that to be correct. That said, some components in a circuit are location critical. Capacitors for example often times need to be location specific.

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