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→Probe Readout Ring Decoder
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==Probe Readout Ring Decoder== | ==Probe Readout Ring Decoder== | ||
The M94 has a circuit for decoding the probe attenuation factor based on the probe readout pin. | The M94 has a circuit for decoding the probe attenuation factor based on the probe readout pin. | ||
The probe readout pin contacts the readout ring on the probe input of the scope. | The probe readout pin contacts the readout ring on the probe input of the scope. | ||
The readout ring is pulled up to 5 volts by a 5 kΩ resistor outside of the M94. | The readout ring is pulled up to 5 volts by a 5 kΩ resistor outside of the M94. | ||
Inside the probe, there is a resistor between the readout pin and the ground of the BNC connector. | Inside the probe, there is a resistor between the readout pin and the ground of the BNC connector. | ||
This scheme allows the scope to distinguish 1x, 10x, and 100x probes, and adjust on-screen readout scale accordingly, | This scheme allows the scope to distinguish 1x, 10x, and 100x probes, and adjust on-screen readout scale accordingly, | ||
so that the on-screen scale is referenced to the voltage at the probe tip. | so that the on-screen scale is referenced to the voltage at the probe tip. | ||
Letting the ring float represents a 1x probe. | |||
11 kΩ to ground represents a 10x probe. | 11 kΩ to ground represents a 10x probe. | ||
6.2 kΩ to ground represents a 100k probe. | 6.2 kΩ to ground represents a 100k probe. | ||