From the Expert

From the Expert

SmartTach Frequently Asked Questions

Q. How do I to measure RPM on diesel engines?
A. There are two methods. You can use an optical sensor from ATI to measure a painted stripe on a rotating part of the engine. You can also use an existing electrical signal that correlates to the engine RPM. Example signals include a Tachometer driver or and electronic injector signal.

Q. How do I to measure RPM on engines without spark plug wires?
A. The optional TS1 probe from ATI can be used to measure RPM from the coil primary wire on all conventional spark ignition engines. Note that this approach will not work on CDI type ignitions. You can also connect a wire from the coil negative wire directly into the pulse input connector on the back of the SmartTach; make sure parameter P-06 is set to SPK or damage may occur to SmartTach circuitry.

Q. What is the SmartTach’s Intelligent Signal Conditioning?
A. It is the ability of the SmartTach to dynamically configure the signal conditioning when using magnetic sensors or digital pulses. Inputs can be automatically configured for all type of sensor signals. Note, however, that it is impossible to automatically determine the correct trigger edge of the signal that should be used, therefore this detail (P-21) should be set as required.

Q. What is the proper function of the SmartTach's display?
A. The display will always show a digital RPM reading:

  1. If there is no display, the unit may not be connected to power.  NOTE: the display can also be toggled off/on by pressing the Enter button; check the setting. 
  2. If there is no RPM reading or a constant unexpected zero, check settings per the thorough Trouble Shooting section of the product manual. There are additional settings available offering more features, but if not set correctly, they may cause unexpected readings. 
  3. If there is an erratic reading, check the following: 
    • Possible bad inductive probe / wiring.
    • Noise from ignition system, try to measure the RPM from the coil wire, set P-02 for number of cylinders.
    • Noise from power supply or data acquisition system.
    • Use filter P-07 to average RPM reading; set it as high as necessary to smooth the reading, but be aware that filtering will affect the response time to changes in RPM. 
    • Improper setting for type of signal, adjust threshold, etc...
  4. If the reading seems to be a multiple or fraction of what is expected (such as half or triple the expected reading): Check the P-02 setting for proper number of pulses per Cam Rev (such as 2 Crank rev.s). 


Q. Can the SmartTach be used near spark plug wire cables and ignition coils?
A. All SmartTach cables are shielded, but high frequency noise from the ignition system can penetrate into inputs. Mount the SmartTach and route SmartTach wires away from the ignition system.

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