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Old 09-19-2019, 04:02 PM   #1
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Default Meter issue with low voltage AC

Hey all, I have a Fluke T5-1000 and an Ideal clamp on; have had them both for years and never had a problem. Recently I was troubleshooting a 12V transformer (WAC). I had 120V on the line side and zero on the load side. So, I assumed the transformer was bad. Well, after 3 transformers, I assumed my assumption was wrong. I checked the load side numerous times with both meters and continuously read 120 on the line and 0 on the load. I even checked a couple of AA and 9V batteries and the meter read those fine. I double checked connections were tight and making contact, and I know it's not the transformer cause I decided to go ahead and power it, and it worked without issue. So, anyone have any idea why after years of reliable readings, suddenly both meters simultaneously no longer give a reading on low voltage alternating current? I even tried it on other types of 12V transformers and got nothing.
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Old 09-19-2019, 05:45 PM   #2
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on the load side you wire to to wire not to ground?
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Old 09-19-2019, 06:03 PM   #3
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Default AC or DC

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Originally Posted by Johnny821 View Post
Hey all, I have a Fluke T5-1000 and an Ideal clamp on; have had them both for years and never had a problem. Recently I was troubleshooting a 12V transformer (WAC). I had 120V on the line side and zero on the load side. So, I assumed the transformer was bad. Well, after 3 transformers, I assumed my assumption was wrong. I checked the load side numerous times with both meters and continuously read 120 on the line and 0 on the load. I even checked a couple of AA and 9V batteries and the meter read those fine. I double checked connections were tight and making contact, and I know it's not the transformer cause I decided to go ahead and power it, and it worked without issue. So, anyone have any idea why after years of reliable readings, suddenly both meters simultaneously no longer give a reading on low voltage alternating current? I even tried it on other types of 12V transformers and got nothing.
You said you had a problem reading low AC voltage but DC was OK. Is the Xformer a plug in type?
Is it a power supply or xformer?
Did you check for both AC and DC output?
Sounds like meter was set wrong and you were looking for AC coming out of a DC power supply.
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Old 09-19-2019, 06:11 PM   #4
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You said you had a problem reading low AC voltage but DC was OK. Is the Xformer a plug in type?
Is it a power supply or xformer?
Did you check for both AC and DC output?
Sounds like meter was set wrong and you were looking for AC coming out of a DC power supply.
The T5 only has 1 voltage setting, it senses AC or DC.
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Old 09-19-2019, 06:39 PM   #5
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If it's an electronic ballast type Tx, some of them need a load to turn on.

If you can, measure now that the lights are on.
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Old 09-19-2019, 07:54 PM   #6
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The T5 only has 1 voltage setting, it senses AC or DC.
That why i love that meter. Saved me from lighting my arse up on a auto-meg tester many times.
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Old 09-19-2019, 08:22 PM   #7
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Thanks all for the replies. I did test it wire to wire, and as mentioned the T5 is duel current, the Ideal meter was set to AC, but I tried both for the hell of it. It is not a plug in transformer, it is a hardwired low voltage power supply for WAC low voltage lighting. I think that answers everyone's responses so far...
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Old 09-19-2019, 09:07 PM   #8
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it is a hardwired low voltage power supply for WAC low voltage lighting.
Emtnut is probably correct and the power supply is not going to switch on until it senses a load. Probably some scientific explanation like the gates inside the supply require a feedback path to control the switching speed blar blar blar.
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Old 09-19-2019, 09:16 PM   #9
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I get that, but have used these same exact transformers before and measured 12V without a load. I will try another meter on a different transformer.
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