Nah, just figured you would know the resistance of the circuit and would be able to back calculate voltage after measuring the current. Ian McLean wrote: >Yer thanks Shawn, but my question is regarding sensing AC voltage, not >current. Did you misread this, or am I missing something? > >I have looked at many options for sensing AC current, including the hall >effect sensor approach as used by these Allegro chips. In the end, I >decided for the power levels I am measuring (up to about 50A AC, or approx. >12kW), the easiest solution was using a 50:5 CT, with a TVS diode and burden >resistor on the secondary output of the CT. This works great for monitoring >average AC current. Thanks to those on this list just recently for their >advice concerning this. > >Rgs >Ian. > > > >>-----Original Message----- >>From: pic microcontroller discussion list >>[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Shawn Wilton >>Sent: Thursday, 15 April 2004 1:51 am >>To: PICLIST@MITVMA.MIT.EDU >>Subject: Re: [EE:] AC Voltage measurement >> >> >>Yeah, go to Allegromicro.com and pick up some of their current sensing >>chips. >> >> >>Shawn Wilton >>Junior in CpE >>MicroBiologist >> >>Phone: (503) 881-2707 >>Email: shawn@black9.net >> >>http://black9.net >> >> >>Ian McLean wrote: >> >> >>>Hi all, >>> >>>Could someone point me somewhere or give some advice on >>> >>> >>monitoring 240VAC >> >> >>>50Hz mains voltage using PIC A/D. >>> >>>The reason I wish to do this is to display the output of a >>> >>> >>variac on an LCD >> >> >>>panel. >>> >>>Immediate methods that come to mind are: >>>a) Step down the mains with a step down transformer, >>> >>> >>rectify the output, >> >> >>>filter, and resistive voltage divider. >>>b) Leave the step down transformer out of the equation, and >>> >>> >>use higher >> >> >>>voltage rated filter caps, and a bigger resistor divider. >>> >>>Both the above methods could empoy a level of PIC >>> >>> >>protection by using an >> >> >>>op-amp configured as a voltage follower with no gain to >>> >>> >>clip the output to >> >> >>>the AD 5V rail limit. I figure both methods should give a >>> >>> >>reasonably enough >> >> >>>linear output. >>> >>>I can see problems with both of these methods however, >>> >>> >>particularly in >> >> >>>regards to ground rail impedance caused by the high voltage >>> >>> >>divider, esp. in >> >> >>>option(b), and causing major headaches for the low voltage >>> >>> >>ground reference >> >> >>>side for the digital electronics. Can anyone suggest a better way ? >>> >>>Hmmm. Maybe I should have just stuck with the simple >>> >>> >>moving iron meters ;) >> >> >>>Regards, >>>Ian >>> >>>-- >>>http://www.piclist.com#nomail Going offline? Don't AutoReply us! >>>email listserv@mitvma.mit.edu with SET PICList DIGEST in the body >>> >>> >>-- >>http://www.piclist.com#nomail Going offline? Don't AutoReply us! >>email listserv@mitvma.mit.edu with SET PICList DIGEST in the body >> >> > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body