AVR-Chat

Hi Ned,

Thanks a lot... Actually, i saw that IC on the net when i was searching for a solution.. But im having difficulty to find the IC. I am in singapore and i buy components from farnell only. Farnell singapore doesnt have LT6102. I dunno any electronics store here. Since a lot of guys are suggesting to put the sense resistor at the low side, i am planning to implement this and see how good this idea.

regards,
mago 

Ned Konz <ned@bike-nomad.com> wrote:                                  magzky02 wrote:
 > Hello all,
 > 
 > I am going to measure the current (0-500mA) on a system. i will be 
 > using a current sense resistor, and an op-amp then i use ADC to 
 > measure the opm-amp output. But my problem is that the the line is 
 > high voltage (70 V). I am thinking to isolate the ground of the the 
 > line and the ground of my monitoring box. In this case, the monitoring 
 > box will not sence the 70 volt line as 70 volt, but will just measure 
 > the voltage drop accross the current sense resistor. A idea on how to 
 > measure current on high voltage systems is highly appreciated?
 > 
 
 There are a number of current-sense amplifiers that do level shifting 
 from high voltages.
 
 For instance,
 http://www.linear.com/pc/viewCategory.jsp?navId=H0,C1,C1154,C1009,C1077
 
 shows a table of Linear Technology's "current sense amplifiers".
 
 They have two parts that should do the job (they'll go to 100V 
 common-mode voltage):
 
 LT6102HV
 http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1009,C1077,P38188
 
 LT6101HV
 http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1009,C1077,P12995
 
 These differ mostly in accuracy -- the LT6102HV is a zero drift, 
 precision unit with 3mV max of offset voltage, while the LT6101HV has a 
 maximum of 85mV of offset voltage (which may be higher than the 
 current-sense voltage you're trying to monitor!).
 
 They have a current-mode output, so you set the overall gain by the 
 choice of an output resistor, whose other end is tied to ground.
 
 Linear is selling the LT6102HV for 2.93 in single-unit quantities on 
 their web site (SO-8 package).
 
 -- 
 Ned Konz
 ned@bike-nomad.com
 http://bike-nomad.com
 
     
                       

       
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