Digital volt and amp meter humming / buzz

[Mr Googler]

Since getting the boat, I have had a very annoying high pitch hum coming from the electrical panel. It changes under more draw or when on charge. I have isolated it to 2 digital displays, one for volts and one for amp draw.

Once they are unplugged, the sound goes......very technical diagnosis pathway!

These are certianly after market additions so my question before I buy replacements is, do all digital display meters do it? Could anything such as the way they are wired cause it?

Any thoughts welcomed

 

[Lon nan Gruagach]

Since getting the boat, I have had a very annoying high pitch hum coming from the electrical panel. It changes under more draw or when on charge. I have isolated it to 2 digital displays, one for volts and one for amp draw.

Once they are unplugged, the sound goes......very technical diagnosis pathway!

These are certianly after market additions so my question before I buy replacements is, do all digital display meters do it? Could anything such as the way they are wired cause it?

Any thoughts welcomed

If they show the right reading then they are wired correctly.
These are the first I have heard of making a noise, but its not unbelievable. Given that 2 of them do the same then its a batch or manufacturer fault. First, try each individually (bet you did that already). Next buy one or 2 from eBay, you would have to have very poor luck to get the same problem.
Most likely reason for a noise is that the display digits are multiplexed, only one digit is illuminated at a time, if the circuit track to one digit is loose, it can vibrate....

 

[elton]

Suggest you tighten the screws on any heat sinks, and squirt "hot glue" over any coils or transformers, to dampen any vibration, giving consideration to cooling.

 

[Mr Googler]

I took this apart today and found a little orange thing that when I touched, the buzzing went quieter. To be honest, I would like something a bit nicer so can anyone identify the manufacturer?

The wiring colours at the back are just red and black, I can't for the life of me find the shunt so if I can identify the maker / model, I can figure it out from the plug layout. There is a sticker on the unit (which is about 12cm long surprisingly) but no manufacturer.

The model number on the sticker is 71105403 if it helps.

Anyone recognise the "D" logo?

 

[BartW]

can you post a picture of that orange thing ?
I guess it is a coil or a capacitor that is vibrating or resonating with the refresh frequency of the display,
or sampling freq from a DC - DC convertor,
try to find the exact component that produces the humming,
If it doesn't get hot,
just put a good amount of silicones or sicaflex over it, and the humming will be gone.

FYI
the V-meter should be connected somewhere to the 12V supply
the A-meter should be connceted to a shunt, but that shunt will be somewhere in the main (thick) 12V supply cable...

 

[Mr Googler]

Thanks Bart. I did just that with an adhesive silicone! I wasn't sure I was supposed to but at least now I can say "Bart told me to!"

I am back down the boat tomorrow so will see if it's help. I found the shunt in the engine room by the battery box so in truth, I think I will replace the whole lot over the winter.