Re: Servo/Spindle motor ammeters?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dennis Schmitz"
<denschmitz@...> wrote:

>
> It depends on how much work you want to do. You could build it with
> that chip, but I have doubts that you could drive the reference

input

> with the internal voltage reference. To get the voltage reference

down

> to where the full-scale voltage at the current sense resistor is,
> you'd need to connect a resistor somewhere in the range of 100k to

1M

> between the ref out pin7 to the ref in, pin6. It wouldn't be very
> linear, but it should work.
>
> A better solution would be to drive the ref in (pin 6) with a

buffered

> reference voltage.
>
> It depends on your purpose -- if it's a quick glance indicator of

when

> you're in trouble, the resistor between pin 7 and pin 6 should work
> fine.
>
> If you tell me the full-scale current and the value of the current
> sense resistor, I'll tell you what value to use and how to hook it

up.

>
> On 7/13/06, afogassa <afogassa@...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dennis Schmitz"

<denschmitz@> wrote:

> > >
> > > Don't do that, open up the drive and find the current sense

resistor

> > > and hook one of these across it:
> > >
> > >

http://newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/partDet
ail.jsp?SKU=01K5532

> > >
> > I want that too..., but I was thinking about a bargraph

indicator,

> > could that be made with a lm3914 it's a bargraph driver ?
> >
> > Fogassa
>

I'm using rutex drives, it's 0.05 ohm resistor and I'm expecting
about 15 amps full scale.
I'm wondering if lm3914 has a high impedance input to not change
the sense resistor value.

Fogassa