So, I tried the new converter and I can't get it to work properly.
It seems to be position sensitive. If I move it just in the right position it will work fine for a while, then it will stop working or show wrong speed, then it will come back to normal....
Here's what I tried:
-Suspected the wiring since it really looks like intermittent operation, so I changed it. I'm using 3 wire shielded cable. Converter located at back of the car so it's closer to the sensor and less susceptible to noise.
-Soldered wires straight to board in and out (no db9 connector)
-Removed 1k resistors in series with outputs
-wrapped converter in tin foil and tied foil to cable shield
-tried different sensitivity settings
-hooked up scope to sensor... signal looks clean
-hooked up scope to converter output, and I was able to read speed without problems... moving the converter/wires around never created an issue. Square wave coming out of it is a bit weird: 5v then ramps down to maybe 3 V goes to 0V and ramps up to maybe 2 then back to 5V...repeating the cycle. I've seen my scope do this when frequency is low...not too worried about it right now.
SO, since it worked with the scope hooked up I figured the internal resistance might have something to do with it. I connected 100k resistor to gnd and tried again (no scope connected) but still doesn't work
Here's a screenshot of a log while driving... so the converter is loose, possibly moving around.
Is it possible to log the actual pulses coming on the input? Any ideas what's causing this?