Using DMM battery to power sensor?

[Melodolic]

I want to build the gauss meter mentioned in another thread, and would like
to make it self-contained (ie, no external battery and regulator). However,
the -ve test lead socket isn't hard-wired to the battery's -ve terminal -
commoning them doesn't work.

Is it possible to use the meter's battery to power the hall-effect sensor
while still powering the meter, such that the voltage from the sensor (0-5V)
can be read by the meter? Some trickery with diodes, perhaps?

 

[Pooh Bear]

I want to build the gauss meter mentioned in another thread, and would like
to make it self-contained (ie, no external battery and regulator). However,
the -ve test lead socket isn't hard-wired to the battery's -ve terminal -
commoning them doesn't work.

Is it possible to use the meter's battery to power the hall-effect sensor
while still powering the meter, such that the voltage from the sensor (0-5V)
can be read by the meter? Some trickery with diodes, perhaps?

You'll need to provide isolation e.g using an inverter.

Graham

 

[Jamie]

I want to build the gauss meter mentioned in another thread, and would like
to make it self-contained (ie, no external battery and regulator). However,
the -ve test lead socket isn't hard-wired to the battery's -ve terminal -
commoning them doesn't work.

Is it possible to use the meter's battery to power the hall-effect sensor
while still powering the meter, such that the voltage from the sensor (0-5V)
can be read by the meter? Some trickery with diodes, perhaps?

sure i don't see why not?
of course if your trying to get a null effect you
may need to use a DC-DC converter to generate
a - voltage.
all this can be done from the DMM's power source.
i suppose one could mod its DMM case to have an
extra connector plug for the HALL sensor and mini
DC-DC on daughter board inside. i did that to an
older meter to add a temp function to it! added the
require electronics to read a J type thermo couple .
all i had to do was put the meter on the volt scale
and turn on the little mini switch.

 

[Melodolic]

You'll need to provide isolation e.g using an inverter.

Righto - looks like a DC/DC converter is the way to go.

 

[Melodolic]

of course if your trying to get a null effect you
may need to use a DC-DC converter to generate
a - voltage.

I've found an isolated DC-DC converter that should do what I want (3ukp from
Rapid Electronics).

all this can be done from the DMM's power source.
i suppose one could mod its DMM case to have an
extra connector plug for the HALL sensor and mini
DC-DC on daughter board inside. i did that to an
older meter to add a temp function to it! added the
require electronics to read a J type thermo couple .

That's the basic idea, yes. A 3-way connector for the sensor cable, with all
the other bits inside.

all i had to do was put the meter on the volt scale
and turn on the little mini switch.

I had a look inside the meter I'm going to use, and found the point where
the power is switched on, so I'll connect the converter to that.