Info

Time

The A/D converter changes the analog signal to this binary language by taking samples of the analog signal at a frequency known as the sampling rate. The converter measures the wave and assigns a digital value to it. The higher the sampling rate, the closer the digital signal comes to representing the analog one. In most cases each sample is divided into eight bits. Each bit is assigned either a "0" or a "1". These eight bits are called a word. As illustrated (below), whenever the A/D converter samples the signal, it assigns a binary number to the voltage at that point (which the computer reads as a series of "ONs" and "OFFs"), and slices up the wave like a loaf of bread.

DIGITIZING AN ANALOG SIGNAL

DIGITIZING AN ANALOG SIGNAL

With the signal converted to eight-bit words, the computer can use the data from the sensor. The computer then sends out instructions in the form of a digital signal to an actuator. In most cases this works because most actuators are solenoids or stepper motors which operate on digital commands.

There are, however, some components such as blower motors or the power steering pump motor on the 1991 MR2, that require variable voltage to operate motors at variable speeds. In such cases, the computer uses a D/A converter to change the digital signal to analog. The principles of D/A converter operation are the same as the A/D converter. The pulses of voltage coming from the computer are converted to variable voltage.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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