How to test a Fluorescent Tube?

glassescase · Post by **glassescase** » Mon Nov 28, 2022 1:20 pm

How to test a Fluorescent Tube?
I watched video on YouTube which made it look easy, set multimeter to ohms, put probes on end of tube and hay presto, so I tried it.
My digital multimeter flashes away like it is demented. I cannot get a steady reading. The video shows I should get about 3 ohms.
What scale of ohms should the meter be set to? I have 200, 2k, 200k and 2M.

thanks

glassescase

Someone-Else · Post by **Someone-Else** » Mon Nov 28, 2022 1:24 pm

Have you tried another tube? It may be the one you are testing has failed.

glassescase · Post by **glassescase** » Mon Nov 28, 2022 1:30 pm

Someone-Else wrote: ↑Mon Nov 28, 2022 1:24 pm Have you tried another tube? It may be the one you are testing has failed.

If the tube has failed, what would my set results be? I would not expect to get any ohms reading but I do not know how to test a Fluorescent Tube so no idea what to expect.

Yes tried another tube and that is the same. They have never worked since we got the house. I tried to prove power to the switch but that seemed to have shown no power so will hook up a temporary supply but would still like to know about testing a Fluorescent Tube.

glassescase

Someone-Else · Post by **Someone-Else** » Mon Nov 28, 2022 2:21 pm

If you set your meter to the highest range and put your leads on the tube (same end) you should get a reading, if you don't the tube has failed.
If you do get a reading you could turn the range down until it is too high (gives no reading)
Do test your leads first.

ericmark · Post by **ericmark** » Mon Nov 28, 2022 10:57 pm

You can test the tubes heaters with a multi-meter, but you can't test the tube. With a HF ballast often the heaters are not used, so even when the tube is at end of life, heaters will show A1.

Also using a multi-meter on a fluorescent can blow the meter, the strike voltage can be very high, modern meters do tend to fair better, but I wrecked a AVO Mk8 testing an inverter supply, so be warned.

Fluorescent lights have always caused problems testing, fly catchers used special starters, and some water treatment plants the tubes use a lot of power, to give out UV light. I simply tested the tube by trying with a new one.

glassescase · Post by **glassescase** » Tue Nov 29, 2022 8:31 am

ericmark wrote: ↑Mon Nov 28, 2022 10:57 pm You can test the tubes heaters with a multi-meter, but you can't test the tube. With a HF ballast often the heaters are not used, so even when the tube is at end of life, heaters will show A1.

Also using a multi-meter on a fluorescent can blow the meter, the strike voltage can be very high, modern meters do tend to fair better, but I wrecked a AVO Mk8 testing an inverter supply, so be warned.

Fluorescent lights have always caused problems testing, fly catchers used special starters, and some water treatment plants the tubes use a lot of power, to give out UV light. I simply tested the tube by trying with a new one.

Oh. The YouTube video made it look so easy!

Yesterday I took the light switch apart and removed the cables. Taking pot luck I connected a temporary power supply to one cable and hey presto the fluorescent tubes in one of the lights burst into life. An Educated guess when connecting the temporary supply to the next cable and a second set of lights burst into life. I will reassemble the strip light I have removed the tubes from and connect a temporary supply to the third cable and keep my fingers crossed.

It could be the fault was in the feed to the switch. When I removed this cable it very much looked like it had been damaged and a wire severed. I tested the cable before removing and could not prove continuity but could not believe the cable was faulty to took a strip light apart. I should have believed the science!

glassescase