Rpm square wave

[unsyndicated]

Apologies if its been discussed before.  I've tried searching but with no luck. 

I have msd 7al3 ignition box, I'm attempting to see if I can output its tach signal to a BRX high speed input.  The 7al3 outputs  12vdc square wave signal.  Would the BRX be able to capture the signal?

[BobO]

BRX inputs should work down to 9v and speed is likely be plenty fast an ignition. The BX-HSIO4 module has differential inputs that work down to TTL levels and is even faster.

[unsyndicated]

Perfect we'll be spinning at 10k rpms and wanted to see if I could build my own digital display and data logger. 

[BobO]

Perfect we'll be spinning at 10k rpms and wanted to see if I could build my own digital display and data logger.

Easy. 10K RPM is only 166Hz, nothing at all. For something that slow, you may want to use a timer with interval scaling.

Fun fact: Host did some telemetry for ADC's TransAm car many years back. I was trying to get good numbers from a wheel speed sensor and was struggling with the high speed counter being too slow and crunchy to provide good rate numbers. So rather than counting rotations, I switched over to timing them. That was the inspiration for the Free Run Edge Timer w/Interval Scaling that got added to the CTRIO, and then eventually to BRX.

[unsyndicated]

sounds like you have given me another idea, might just have to put a sensor to measure wheel speed.  Now to figure out air/fuel ratio logging.

[BobO]

sounds like you have given me another idea, might just have to put a sensor to measure wheel speed.  Now to figure out air/fuel ratio logging.

Good luck!