I'm hoping some of the EE's or educated hobbyists here can help me with this challenge.
I have a Mass Air Flow sensor for which I want to increase the output signal for the lower part of the output range. Here is a link to the closest thing to a datasheet that's available (pages 1-3)...http://www.autoshop101.com/forms/h34.pdf
My particular sensor has a DC offset of ~0.7V at STP, and a max. output of ~4.8V. The lookin resistance (measured with a voltmeter) across VG and E2G = 28k.
What I want to do is add about +200mV DC offset to the lower range of the output where VG < ~2V.
Specifically, where VG = 1.5V currently, I want the modified output VG' = 1.7V.
I'd be happy with either of the following solutions that have VG' = 1.7 when VG = 1.5...
- an offset of 200mV across the full range [VG' = VG + 0.2]
- offset > 200mV at VG = 0 , and nearly-zero offset for VG=4.8V [i.e. VG' = VG + (4.8-VG)*0.06]
Whatever the solution I strongly prefer passive components.
I've played around with LTspice and can almost get what I want by simulating the sensor output as a voltage source, and connecting +2V to the +ve side of the source through a diode. But not quite, and I don't *really* know what I'm doing. (I tried a reverse-biased Zener diode too, which seemed even closer, but was sensitive to series resistance of the source and again, found I didn't know what I was doing.)
I've looked at op-amps but I'd prefer not to build a voltage summer circuit, mostly because I think it's possible to achieve what I want through careful selection of some sort of diode and a few resistors.
Help, either in the form of search keywords or comments and discussion is appreciated.
FWIW I have easy access to +12V and +5V DC.
Thanks to anybody interested enough to offer some friendly help