any electrical engineers?

C

cooper1203

Member
hi all I want to test the voltage signal to the left hand indicator tell tail light on the dash. I am assuming that as the voltage switches on and off it is effectively a square wave I doubt my meter on the dc volts setting would register it properly (its cheap) if I set it to the ac setting would it pick up a square wave or does it have to be a sine wave???

if it does pick it up on the ac settings would I get a rms or peek voltage??

many thanks
coop
 
The blink rate is surely slow enough to register on/off on any meter on the DC setting?

Most AC meters won't work well much below 50Hz of mains electricity, certainly not in the 1-2Hz range.
 
What you really need is a DC moving coil meter, the kind with a needle. You'll see the needle swing far more easily than numbers changing on a digital display. As Peter says, AC setting won't register anything as the frequency is way too low to be considered as AC and by definition AC alternates between positive and negative values rather than positive and zero.

If the telltales are not operating as you expect, check the earth to the instruments as that can play havoc with the warning lights. A bad earth forces alternative current paths and you get lamps lighting up when they shouldn't. Bit like the flashing entire rear light clusters you used to see on the back of cars.

Dave
 
Hi Coop,
The required flash rate is 90 per minute, plus or minus 30.
Set your your meter to DC volts, even a cheap meter will pick that up.
As peter said, AC will not. Why are you checking the repeater?

Jim.
 
Digital will not do, a moving coil meter is perfect for this task, and only use the DC range on the meter.

Graeme
 
Hi all thanks for the replies that's pretty much what I guessed. I wanted to check it because I had the dash out and now the left hand indicator tell tail doesn't work. replaced the bulb and it still doesn't work so wanted to make sure I had voltage there. my cheap meter just flickers around b4 u get a chance to see it.

I'm going to go to my friendly garage and see if I can persuade them to put their engine scope on it for a drink

many thanks
coop
 
Rubythursday said:
Why not just bypass the flasher unit, then the voltage will be steady so your cheap meter will work.
Click to expand...

then I have to go digging rather than just testing the holder. and all it will tell me is there is a voltage in front of the unit I would then have to test the other side to find out if it is the unit at fault so back to square one
coop
 
Hi, Are the indicators front and rear flashing OK? If they are then the problem is likely
in the dash area, so as suggested by-passing the flasher can can help fault finding by
ensuring a constant voltage. If the external indicators are not working then I would think
the fault lies in the indicator switch or hazard switch.

Colin
 
hi, the indicators them selves are working fine front and back its just the left hand tell tale. I must be miss understanding what your both suggesting as if I measure the voltage to the flasher unit all that does is prove there is a voltage there but doesn't tell me anything about after the unit surely
coop
 
sorry im not with it last few days u meant connect the "input" of the flasher unit to the output im guessing. I haven't looked properly yet as every time I go near the thing something else crops up needing my immediate attention. is there spade connecters on the flasher unit so I can just short the two wires together??
coop
 
Hi, that's OK, I understand that some people don't 'get' electrickery it being black magic and all.
There are some things I don't get, like for instance flower arranging, what's that all about?
They're not arranged in the wild.

Colin
 
dunno about flower arranging either but I should get electrics as I did an onc in electrical and electronic engineering..... mind u I couldn't never grasp "thevanins therom"
 
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