Receives a US Patent on its Mr Flow Transmitter


Hedland, manufacturer of flow measurement solutions, recently received a US Patent on its MR Flow Transmitter. The new design avoids consuming too much power by activating only portions of the Anisotropic Magnetoresistive (AMR) array electronics in a systematic way. This invention is recognized for its individuality in the industry.

One of the greatest hurdles to overcome when integrating the magnetic sensor technologies into an industrial sensor is they are power hungry. Most are powered and transmit information on the same two wires. Unique to the MR Transmitter is that it does not power all of the MR sensors at once. The microprocessor selects and reads the output voltage of seven AMR sensors, one at a time, until the entire array of sensors have been read. This voltage is routed through a multiplexing circuit and then into an instrumentation amplifier. The signal is amplified, passed through a low pass filter and then input to the A/D converter built into the microprocessor. Based on the readings, the microprocessor determines the absolute position of the magnet inside the flow meter, and calculates the flow rate based upon user selectable setup scaling parameters. The flow rate is then displayed on the LCD display. The unit can also calculate and display the total accumulated flow.

Analog outputs of 4-20mA current loop, 0-5Vdc and 0-10 Vdc are provided. These outputs are calibrated to output an analog current or voltage corresponding to the measured flow rate. The MR Flow Transmitter also has the ability to enter up to 10 linearization points to compensate for the non-linearity of the flow meter.

Hedland's goal was to continue the industry standard of 2-wire, loop-powered 4-20mA. It was accomplished and can hold quiescent current consumption to less than 2mA—resulting in a patent product.
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