Auto ranging current monitor with common mode correction
First Claim
1. A current monitor for measuring a load current level over a wide dynamic range in a circuit having a load supplied by a power source and outputting the load current level to an output device, comprising:
- a low current sensor and a high current sensor connected in series with the load and the power source;
a low current channel having an input connected to the low current sensor and a low current output carrying a low current signal corresponding to the load current level within a low current range;
a high current channel having an input connected to the high current sensor and a high current output carrying a high current signal corresponding to the load current level within a high current range; and
a channel switching circuit responsive to the load current and coupled to said low current sensor and to said high and low current outputs for (1) providing said low current signal to said output device when the load current is below a predetermined thresholds, and (2) short circuiting said low current sensor and providing said high current signal to said output device when the load current is above said predetermined threshold.
1 Assignment
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Accused Products
Abstract
An improved current monitor for measuring current over a wide dynamic range. The current monitor includes a low current channel, a high current channel, and a switch for selecting the low current channel if the measured current is below a predetermined level and the high current channel if the current is above the predetermined level. The output of the high current channel is voltage encoded by adding a fixed offset. The current monitor determines that the measured current is from the low current channel if the reading is below the offset and from the high current channel if the reading is above the offset. A current level output device automatically outputs a decoded current reading based on this determination. The current monitor also incorporates a low current error compensation circuit to compensate for parasitic current when the current monitor is using the high current channel. The current monitor also incorporates a device for reducing the common mode error voltage to zero in the differential amplifiers used to convert current across shunt resistors in the low and high current channels to a voltage signal.
34 Citations
13 Claims
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1. A current monitor for measuring a load current level over a wide dynamic range in a circuit having a load supplied by a power source and outputting the load current level to an output device, comprising:
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a low current sensor and a high current sensor connected in series with the load and the power source; a low current channel having an input connected to the low current sensor and a low current output carrying a low current signal corresponding to the load current level within a low current range; a high current channel having an input connected to the high current sensor and a high current output carrying a high current signal corresponding to the load current level within a high current range; and a channel switching circuit responsive to the load current and coupled to said low current sensor and to said high and low current outputs for (1) providing said low current signal to said output device when the load current is below a predetermined thresholds, and (2) short circuiting said low current sensor and providing said high current signal to said output device when the load current is above said predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A current monitor for measuring a load current level over a wide dynamic range in a circuit having a load supplied by a power source and outputting the load current level to an output means, comprising:
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a low current sensor and a high current sensor connected in series with the load and the power source; low current channel means connected to the low current sensor for measuring the load current within a low current range and developing a low current signal corresponding thereto; high current channel means connected to the high current sensor for measuring the load current within a high current range and developing a high current signal corresponding thereto; and channel switching means responsive to the load current for automatically outputting said low current signal to said output means when the load current is below a predetermined threshold and short circuiting said low current sensor and providing said high current signal to said output means when the load current is above said predetermined threshold. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification