How to check AC current Through multimeter

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Discussion Overview

The discussion revolves around how to measure AC current using a digital multimeter, particularly in the context of household applications. Participants explore the limitations of standard multimeters for this purpose and consider alternative methods for measuring current in specific scenarios, such as with a small indicator lamp.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant requests instructions for measuring AC current with a digital multimeter.
  • Another participant warns that those unfamiliar with measuring household line current may be unsafe due to the risks of dealing with high voltages.
  • A suggestion is made that a regular multimeter is insufficient for measuring AC current, and a clamp-on meter is recommended instead.
  • A participant shares a specific scenario involving a 5.4Vac indicator lamp and describes difficulties in measuring current with a common multimeter, which fluctuates around 40mA.
  • There is a discussion about the necessity of knowing the current draw for finding a suitable replacement bulb, given the voltage and physical size of the original lamp.
  • Another participant suggests that measuring the voltage of the good bulb could provide a close approximation for finding a replacement, proposing the use of batteries and resistors as an alternative method.

Areas of Agreement / Disagreement

Participants express differing views on the safety and feasibility of measuring AC current with standard multimeters. There is no consensus on the best method for measuring current in the specific case of the indicator lamp, as suggestions vary.

Contextual Notes

Limitations include the potential inaccuracy of measurements with low-cost multimeters and the lack of consensus on safe practices for measuring household AC current.

Durai
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Hai Guys...

I want to check the AC current by using digtal multimeter.Please give me instruction.
 
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No,
Sorry - but assuming you mean household line/mains current (ie 120/230V) then anybody who needs to ask is probably not safe dealing with potentially lethal voltages.
 
A regular multimeter won't do. You need a clamp-on meter: http://www.homedepot.com/h_d1/N-5yc1vZ1xgy/R-100047661/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
 
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Thanks russ - I was picturing somebody with a $5 DVM and it's optimistic 10A range trying to measure the current to a water heater.
 
mgb_phys said:
No,
Sorry - but assuming you mean household line/mains current (ie 120/230V) then anybody who needs to ask is probably not safe dealing with potentially lethal voltages.

I have a situation with a very small indicator lamp. The voltage is 5.4Vac. One lamp is burned out (I want to replace both). With a common multimeter in series with the good bulb, the range set to 200mA, the meter fluctuates, maximizing around 40mA. I am trying to reverse engineer the lamp for replacement, and only have a cheapo multimeter.

DSC02932x.JPG


Do you have any suggestions I might use for my situation?

Thanks
 
Well as said above, you can't find the amperage, but why do you want to anyway? You already have the voltage of the lamp...
 
Thanks Russ.

If I know the current draw, the voltage and the physical size I can (maybe) find a replacement bulb. Without the current draw known, the replacement bulb might draw more or less than the original and burn bright or dim.
 
5.3volts (RMS?) AC?

5 volts DC supplied by a mains adapter should be close enough to measure on the good bulb.
Or perhaps you can make up with batteries and a few resistors?
 

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