Speed Conditioning Module

Description

Magnetic speed pickups are typically installed to measure the speed of a turbine. The output of these probes is a sine wave whose amplitude varies with the speed of the turbine shaft. This signal can be difficult to read using digital counter modules for the following reasons:

• The amplitude is low at low speed and might not reach the trigger level of the module. This is particularly critical for measurement at turbine barring speeds.
• The amplitude may be very high at high speeds which may exceed the maximum input voltage level of the module.
• The signal may suffer from electromagnetic interference, causing a fluctuating speed reading.
• The wavelength of the signal may change due to mechanical dimensional inconsistencies, e.g. gear teeth inaccuracies.

The two channel speed input module has been designed to produce a square wave output signal of constant amplitude regardless of input signal. The input filtering reduces noise interference with an option of phase lock loop (PLL) circuit to ignore high-frequency interference.