Converting Wheel Pulse Transducer Outputs to Analog Voltages

To complement our new High Resolution Wheel Pulse Transducer (WPT) encoder product, Michigan Scientific Corporation is offering an add-on to convert encoder pulses to proportional voltages.  The EC-LV (Encoder Conditioner – Linear Voltage) reads the Phase A, Phase B , and Index pulse signals from the WPT and converts them to two analog voltage signals: one proportional to angular velocity, and one proportional to angular position. This is helpful for applications that are not using a data acquisition capable of reading high-speed encoder pulse trains. Separating the frequency-to-voltage electronics from the encoder also allows the WPT to maintain a much smaller profile, increasing the durability and longevity.

The EC-LV is powered in-line with the WPT, so there is no need for a separate power source or cable.  All encoder signals are also passed through the EC-LV, so the customer has access to all data generated by the system.

Customizable Outputs

The Full-Scale Velocity (equal to ±10 Vdc) is set at the factory, with two options.  Standard values are 1,000 and 1,800 RPM, and the customer can select which scale to use with a toggle switch.  Customers can request custom values for the full-scale velocity. Additionally, they can request a custom full-scale voltage, for systems that cannot handle 10 Vdc inputs. There is also a toggle switch to select which rotational direction (clockwise or counter-clockwise) should equate to a positive output.

How it Works

The velocity output of the tachometer board updates on the rising edge of Phase B for positive velocity, and on the falling edge of Phase B for negative velocity. The position output updates on the rising AND falling edge of Phase B. For example, with a 512 PPR (pulse per revolution) WPT, the velocity will update 512 times/revolution, and the position will update 1024 times/revolution.

Presented below are some figures showing the analog voltage outputs of the EC-LV in relation to the encoder outputs of the WPT (passed through the EC-LV).  The EC-LV was set for positive outputs in the clockwise direction for all these figures. The channels are as follows:

  • Channel 1: Phase A
  • Channel 2: Phase B
  • Channel 3: Index
  • Channel 4: either Velocity or Position

The EC-LV is the ideal tool for those using a WPT for testing. They are commonly used in combination for automotive testing and gathering data on wheel speed, vehicle speed, and distance traveled. This is especially important for autonomous vehicle development and road mapping. Contact a Michigan Scientific representative today to begin discussing your WPT and EC-LV application.