Principals of operation Electrolytic
tilt sensor signal conditioning Figure 1 ) is an outline of the basic building block to achieve this result. This flowchart is a representation of the schematic titled “Wide angle single axis
signal conditioner”. This is a description into the operation of an electrolytic
tilt sensor to obtain an electrical output relative to tilt angle. The flowchart below ( Figure 1 Micro-controller
Output ports Analog to Digital input Fredericks Electrolytic Tilt Sensor Let’s start with the micro-controller to define the
sensors excitation. Two output ports are used to drive the
sensors outer pins. These ports are toggled at a 50 percent duty cycle for a recommended period of around 400 hertz. Assuming that the software to toggle these ports is precisely timed to prevent any deviation from a 50 percent duty cycle there should be a minimum of non-symmetry. Non-symmetry can be defined as direct current to the
sensor. Direct current to the
sensor can result in poor performance such as drift. Now that the
sensor has an excitation signal, let’s examine the
sensors output. This signal is a ratio of the excitation signal determined by the tilt of the
sensor. At the null or balanced position the output will be a flat line near the midpoint of the input signal. As the
sensor is tilted in either direction, the input waveform will appear with the amplitude increasing with an increasing tilt angle of the
sensor. The phase of this waveform will depend on which direction the
sensor is tilted. This will indicate positive or negative angles. The signal then goes to a CMOS buffer to prevent any load on the output pin. The output of the buffer is connected to the input of the analog to digital converter in the micro-controller. The micro-controller has the job of processing the signal from the
sensor. Since it knows the timing for the excitation to the
sensor, it needs to take voltage level samples from the
sensor. This is done during each half cycle. Multiple samples during each half cycle are recommended since these can result in a higher bit count and can also be averaged for a more accurate result. One half cycle is subtracted from the other half cycle and the result will be an indication of the tilt angle. The sign of the result will indicate which direction from null that the
sensor is tilted. 1 Sensor excitation Sensor output Buffer - CMOS Operational
Am Bufferedsignal p lifie r
