U1a and U1b cross-coupled Schmidt trigger timers form a ~1 MHz RC multivibrator. The T_SEN pulse width is inversely proportional to sensor displacement

Authors	Stephen Woodward
Main Document	Article «Position sensor gets linear 4 to 20mA current source output»
Description	Figure 1
File Format / Size	PDF / 21 Kb
Document Language	English

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Article «Position sensor gets linear 4 to 20mA current source output»

Figure 1. U1a and U1b cross-coupled Schmidt trigger timers form a ~1 MHz RC multivibrator. The T_SEN pulse width is inversely proportional to sensor displacement
Figure 2. Averaging integrator A1 implicitly computes the output voltage needed to linearly balance the charge transferred onto C1 during T_REF through discharge during T_SEN
Figure 3. Dangling the TLV431 shunt voltage reference Z1 from the 15 volt supply is a shortcut toward implementing a noise- and cable length- tolerant current mode output
Figure 4. In this graph, black = sensor readout d in mm, and red = the nicely constant 4 microamps per micrometer resolution

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Microcontrollers