Using FLUKE1403

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iaraktchiev Participant Join Date: Jun 2008 Posts: 2	Using FLUKE1403 06/03/2008 9:57 PM
	We are testing chargers and inverters. The procedure is to disconnect all PCB and fasten the ground lead to the ground and to touch AC input, DC output. When the unit is tested for a first time DC output shows >550 M ohms. After 2 hours of testing including 1 hour burn test on full load we must test the unit again. Normally we discharge capacitors, closing DC output breaker on the load and disconnecting the batteries. The measurement of DC output to ground gives less than 300 M ohms. Normally First Stage Filter capacitors are 6 in parallel. What is wrong? Why the testing DC output to ground for a first time is showing >550, but finally testing is different? Regards, Ivan Araktchiev
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	Pathfinder Tags: capacitors FLUKE ground

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techno Guru Join Date: Jan 2007 Location: Canada Posts: 1024 Good Answers: 40	#1 Re: Using FLUKE1403 06/04/2008 3:31 PM
	You are checking resistance with capacitors in the cct. To test resistance, a small voltage is passed through the cct. This will charge or discharge the capacitors and give you false readings. The resistance scale is designed to measure true resistance, (not capacitance or inductance) __________________ Perfection is a subjective and abstract concept.
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southern123 Power-User Join Date: Sep 2006 Posts: 367 Good Answers: 1	#2 Re: Using FLUKE1403 06/05/2008 12:30 PM
	It could be "childhood insulation deterioration". And it is normal.
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southern123 Power-User Join Date: Sep 2006 Posts: 367 Good Answers: 1	#3 Re: Using FLUKE1403 06/05/2008 12:35 PM
	Aha.. it is possible that Time Constant of the discharge is hight, over 2 hours. The effect well-known in the HV cables or transformers testing
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Andy Germany Guru Join Date: Sep 2006 Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E Posts: 17996 Good Answers: 200	#4 Re: Using FLUKE1403 06/05/2008 7:30 PM
	Does the value measured change very slowly over say 10 minutes? If yes, you are slowly charging or discharging the caps via the battery in the meter. To get an accurate reading, you need to leave the meter connected till the reading is completely steady. This can take a long period with really big caps..... __________________ "What others say about you reveals more about them, than it does you." Anon.
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