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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Why won't a multimeter work on a 9V plug?
I have several multimeters, including a Fluke and some cheapies.
I wish to use a pair of cheap $2.99 HF meters as dedicated digital panel meters. They work fine on a 9V battery. I would like to hard wire them in. None of the above will work with an AC battery eliminator. I am puzzled by this. Please explain. |
#2
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Why won't a multimeter work on a 9V plug?
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#3
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Why won't a multimeter work on a 9V plug?
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#4
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Why won't a multimeter work on a 9V plug?
In article
, wrote: I have several multimeters, including a Fluke and some cheapies. I wish to use a pair of cheap $2.99 HF meters as dedicated digital panel meters. They work fine on a 9V battery. I would like to hard wire them in. None of the above will work with an AC battery eliminator. I am puzzled by this. Please explain. Measure the output of the eliminator when it's connected to the HF meter. My guess is there's no output from it due to the load being too small which is common with SMPS types. A non SMPS one should work ok - that will be heavier than a similar output SMPS one. Or add a load large enough to switch the SMPS on - an LED and resistor selected to draw 20mA should be enough. 390 ohms in series with a standard red LED should be ok. Make sure you get the polarity of the LED correct. -- *Rehab is for quitters Dave Plowman London SW To e-mail, change noise into sound. |
#5
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Why won't a multimeter work on a 9V plug?
Jamie t writes:
wrote: I have several multimeters, including a Fluke and some cheapies. I wish to use a pair of cheap $2.99 HF meters as dedicated digital panel meters. They work fine on a 9V battery. I would like to hard wire them in. None of the above will work with an AC battery eliminator. I am puzzled by this. Please explain. Most likely you have the newer, worse model Virtual Ground power rail, cheapy meters. Make sure you don't allow the (-)/(+) power lead to come in contact with the (-)/(+) probe of the meter. To clarify (I think): Many digital meters require that the power supply be isolated from the circuit being measured. Also, put a cap and a small load across the wallwart, most likely have one hell of a ripple on it and over voltage. And, make sure the battery eliminator actually measures 9 V without a load, since the meters won't be much of load. -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#6
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Why won't a multimeter work on a 9V plug?
In article ,
Samuel M. Goldwasser wrote: To clarify (I think): Many digital meters require that the power supply be isolated from the circuit being measured. Wouldn't all wall warts do this for class II status? -- *I never drink anything stronger than gin before breakfast * Dave Plowman London SW To e-mail, change noise into sound. |
#7
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Why won't a multimeter work on a 9V plug?
On Jan 14, 10:08*pm, jakdedert wrote:
wrote: I have several multimeters, including a Fluke and some cheapies. I wish to use a pair of cheap $2.99 HF meters as dedicated digital panel meters. They work fine on a 9V battery. I would like to hard wire them in. None of the above will work with an AC *battery eliminator. I am puzzled by this. Please explain. My guess would be that the battery eliminator is a switching type that needs some sort of a load to start up. *Does it weigh less than a few ounces? *If so, it's almost certainly a switcher. Use Ohm's Law to determine a proper resistive load, if it's less than 100 ma. *Put an appropriate resistor across the output and then measure it. *A light bulb of the proper size (which you must determine by the output capacity) would be easier to obtain if the output is more than 100 ma. Post the milliampere rating of the supply here and someone will help you figure the proper load. jak Hi! Thanks. I pulled a 1K trimmer from an old board and set it about half way. Diddled it to see the max resistance effect and it still worked. Works fine! Thanks again BoyntonStu |
#8
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Why won't a multimeter work on a 9V plug?
"Dave Plowman (News)" writes:
In article , Samuel M. Goldwasser wrote: To clarify (I think): Many digital meters require that the power supply be isolated from the circuit being measured. Wouldn't all wall warts do this for class II status? Yes, for a single meter AND with neither power supply connection also attached to one of the meter inputs. And assuming he didn't try to measure the wall wart's voltage with the meter! -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
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