digital ammeter

[owler]

How do I wire a seperate power supply to work a digital ammeter with a shunt to my car.
The instructions say the supply has to be independent and should be 6v to 15v.

I have been warned that to simply wire it through the ignition will blow the ammeter.

Note: An independent DC power is needed to power the meter. A 50A 75mV shunt must be used for this panel meter. The power positive and cathode polarity can't be connected crossly, or it will be damaged.

What does the last sentence mean in simple language?

Its to be used on a HHO system. They give a lead with a 9v battery but its not practical to be replacing batteries all the time. Thanks in advance

 

[JimB]

The power positive and cathode polarity can't be connected crossly, or it will be damaged.

What does the last sentence mean in simple language?

It sounds like Chinglish for "Connect the supply the wrong way round and your meter will be ruined!"

They give a lead with a 9v battery but its not practical to be replacing batteries all the time.

The only thing you can use is an isolating DC to DC converter

JimB

 

[owler]

Hi JimB thanks for the input. Is it possible to built an isolating DC to DC converter easily/cheaply?

 

[JimB]

Hi JimB thanks for the input. Is it possible to built an isolating DC to DC converter easily/cheaply?

I dont know, I never had to do it.
But then again, why would I want to when devices like this:
https://uk.farnell.com/xp-power/ie1212s/converter-dc-dc-1w-12v/dp/8727775
are readily available for a few pounds.

JimB

 

[MikeMl]

Buy a better meter. They allow a common ground between what is being measured and the dc supply that powers the meter. Your cheap meter does not...

 

[jpanhalt]

Can you provide a link to the meter? A lot of "separate supply" meters can be run off the same supply as the measured voltage/current, if you provide a negative-voltage supply, which is just one chip (like the ICL7660) and a few 10 uF capacitors.

John