Tach accuracy
I have found the low cost $20 optical tachs work good. A relective target tape is put on balancer, aim and get a digital read out. I have verified with micro controller timing measurements used in my EFI and ignition systems.
http://www.amazon.com/CyberTech-Digital-Photo-Tachometer-Contact/dp/B001N4QY66/ref=pd_sim_263_1?ie=UTF8&refRID=046BGV1DR4C54R948QW8
I have found the low cost $20 optical tachs work good. A relective target tape is put on balancer, aim and get a digital read out. I have verified with micro controller timing measurements used in my EFI and ignition systems.
http://www.amazon.com/CyberTech-Digital-Photo-Tachometer-Contact/dp/B001N4QY66/ref=pd_sim_263_1?ie=UTF8&refRID=046BGV1DR4C54R948QW8