Need help designing circuit

[LBunting]

By no means am I an electronic whiz - just like my cooking, I can follow a recipe but can't make something on my own. Any help would be appreciated!

I have a flowmeter for a methanol injection system (supra) with a failsafe that will trigger a 12v source if the flow is less than 500cc/min. However, I want it to be able to trigger anywhere up to 2000 cc/min. Here's my in -> the unit has an output for a flowgauge that output's 0.1 V / 100cc of flow up to 2500 cc/min. So, 1000cc/min would output as 1 volt.

So, I need a circuit that Vin is the flow output (.5-2v, .1 sensitive). When Vin < Vset, it triggers a 12v output. It would be nice to make Vset adjustable with a pot.

BTW, trigger would run a 12v, ~3amp relay.

 

[MikeMl]

Do you have a source of 12VDC to power the added circuit?
What is the coil resistance of the 12V relay you want to swtich?
How much hysteresis should the circuit have so that the relay doesn't chatter?
How noisy is the flow signal; i.e. should it be filtered before the trip decision is made?
How do you want to set the trip point? **broken link removed**? Screwdriver adjust trim pot?