It depends on the model of the VM1000. Those purchased from VM before sold to JPI had Hall effect amp meters, those purchased from JPI had shunts (the JPI VM1000 was JPI's 930 in a VM1000 case). Bruce WWW.Glasair.org -----Original Message----- From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Bill Hogarty Sent: Friday, December 09, 2011 7:17 PM To: lml@lancaironline.net Subject: [LML] VM 1000 enginemoniter Westach wants to know if the Vision Microsystems VM 1000 engine monitor uses a hall effect sensor or an a/c voltage. I have no idea. Anybody know??? thanks, Bill Hogarty -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html