Field transmitter built-in test equipment
First Claim
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1. A measurement transmitter coupling to a two-wire process control loop, comprising:
- two terminals for coupling to the two-wire process control loop;
a sensor for sensing a process variable;
circuitry for transmitting the process variable over the two-wire loop;
current setting circuitry for setting a current through the two-wire loop to a first current level and to a second current level;
voltage sense circuitry providing a sensed voltage output related to a sensed voltage potential between the two terminals; and
a microprocessor coupled to the voltage sense circuitry and the current setting circuitry for calculating loop resistance of the two-wire current loop based upon a difference between the first and second current levels and a first voltage potential sensed at the first current level and a second voltage potential sensed at the second current level.
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Abstract
An improved error detection for microprocessor-based transmitters in two-wire process control loops operating in the process control industry. In particular, techniques are shown which are useful in solving malfunctions or failures of microprocessor-based transmitters. When the transmitter is energized, the impedance of the process loop cabling is resolved and stored, displayed or transmitted as desired. The loop impedance is used to calculate potential of a power supply used to power the control loop. This information is used in testing the two-wire loop.
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Citations
8 Claims
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1. A measurement transmitter coupling to a two-wire process control loop, comprising:
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two terminals for coupling to the two-wire process control loop; a sensor for sensing a process variable; circuitry for transmitting the process variable over the two-wire loop; current setting circuitry for setting a current through the two-wire loop to a first current level and to a second current level; voltage sense circuitry providing a sensed voltage output related to a sensed voltage potential between the two terminals; and a microprocessor coupled to the voltage sense circuitry and the current setting circuitry for calculating loop resistance of the two-wire current loop based upon a difference between the first and second current levels and a first voltage potential sensed at the first current level and a second voltage potential sensed at the second current level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification