Patent ID: 9020768
Filing Date: 2015-04-28
Classification: G08C

Abstract:
1. A process variable transmitter, comprising: a processor receiving an input signal indicative of a sensed process variable and outputting a digital signal indicative of the input signal; a digital-to-analog (D/A) converter receiving the digital signal and converting it to an analog signal; a loop control component receiving the analog signal and controlling a two-wire process control loop based upon a voltage generated across a resistive element coupled in series with the two-wire process control loop to provide a transmitter output signal indicative of the analog signal, the transmitter output signal varying, on-scale, between a first signal level and a second signal level; and a loop diagnostic component including an analog comparator which compares a first signal value indicative of the analog signal from the D/A converter with a second signal value indicative of the transmitter output signal to determine whether the transmitter output signal includes an on-scale error and responsively outputting an error indicator to the processor; wherein the second value is generated as a function of the voltage across the resistive element.