2-Wire, 4-20mA Smart Signal Conditioner

 

Part Number	Replacement	Explanation

Description

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The MAX1459 highly integrated analog-sensor signal conditioner is optimized for piezoresistive sensor calibration and compensation with minimal external components. It includes a programmable current source for sensor excitation, a 3-bit programmable-gain amplifier (PGA), a 128-bit internal EEPROM, and four 12-bit DACs. Achieving a total error factor within 1% of the sensor's repeatability errors, the MAX1459 compensates offset, offset temperature coefficient (offset TC), full-span output (FSO), FSO temperature coefficient (FSOTC), and FSO nonlinearity of silicon piezoresistive sensors.

The MAX1459 calibrates and compensates first-order temperature errors by adjusting the offset and span of the input signal through digital-to-analog converters (DACs), thereby eliminating quantization noise.

The MAX1459 allows temperature compensation via the external sensor, an internal temperature-dependent resistor, or a dedicated external temperature transducer. Accuracies better than 0.5% can be achieved with low-cost external temperature sensors (i.e., silicon transistor), depending on sensor choice.

Built-in testability features on the MAX1459 result in the integration of three traditional sensor-manufacturing operations into one automated process:

• Pretest: Data acquisition of sensor performance under the control of a host test computer.
• Calibration and compensation: Computation and storage (in an internal EEPROM) of calibration and compensation coefficients computed by the test computer and downloaded to the MAX1459.
• Final test operation: Verification of transducer calibration and compensation without removal from the pretest socket.

Although optimized for use with piezoresistive sensors, the MAX1459 may also be used with other resistive sensors (i.e., accelerometers and strain gauges) with some additional external components.

MAX1459: Functional Diagram Enlarge+

Key Features

• Highly Integrated Sensor Signal Conditioner for 2-Wire, 4-20mA Transmitters
• Sensor Errors Trimmed Using Correction Coefficients Stored in Internal EEPROM-Eliminates the Need for Laser Trimming and Potentiometers
• Compensates Offset, Offset TC, FSO, FSOTC, FSO Linearity
• Programmable Current Source (0.1mA to 2.0mA) for Sensor Excitation
• Fast Signal-Path Settling Time (approximately 1ms)
• Accepts Sensor Outputs from +1mV/V to +40mV/V
• Fully Analog Signal Path
• Internal or External Temperature Reference Compensation
• Automated Pilot Production (Calibration/Compensation) System Available
• Write Protection for EEPROM Data Security

Applications/Uses

• 4mA to 20mA Transmitters
• Industrial Pressure Sensors
• Load Cells/Wheatstone Bridges
• Piezoresistive Pressure and Acceleration
• Strain Gauges
• Temperature Sensing and Monitoring