----- Original Message ----- From: "Spehro Pefhany" To: "Microcontroller discussion list - Public." Sent: Thursday, September 10, 2009 7:49 AM Subject: Re: [EE] two wire inductive magnetic gear tooth sensor circuitry > At 11:12 PM 9/9/2009, you wrote: >> > The OP has not provided enough information to allow anyone to do more >> > than >> > make guesses at what he has and what he needs. >> >>I would strongly recommend that the original poster see what happens if he >>treats the sensor as a current loop device: >> >>Connect +24V to +ve lead of sensor >>Connect -ve lead of sensor to load resistor (250 ohms or so) >>Connect other lead of load resistor to ground >>Scope signal across load resistor >> >>If the device is indeed 4-20ma current loop, then the signal should swing >>somewhere between 1 and 5 volts. >> >>-- Bob Ammerman > > If the signal goes up to a large DC value, slowly changes over the next > few minutes, then makes an abrupt change, then you know it is > (was, actually) a VRS. ;-) The OP has *already* applied 24V to the sensor (without a series resistor) and it seems to generate a low-level sinusoid(?) superimposed on the supply voltage. This test apparently didn't fry the sensor, so it probably isn't a (bare) VRS. I am assuming he has a high enough impedance power supply that the device is able to force it up and down the 50mv he is seeing. If the sensor is really a 4-20ma device the 50mv signal would indicate a source impedance of the power supply on the order of 2.5 ohms, which seems rather high, however. -- Bob Ammerman RAm Systems -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist