Method for checking an automation technology field device during operation, and corresponding field device

A method for online checking a field device for determining and/or monitoring at least one process variable of a medium, wherein the field device has a sensor unit and a control/evaluation unit with a first measuring channel formed by a first preprocessing block, a second measuring channel formed by a second preprocessing block, and a verification channel formed by a configurable third preprocessing block, the method comprising:

• generating in the sensor unit a first sensor signal dependent on the at least one process variable;
• transmitting the first sensor signal to the first measuring channel;
• generating in the sensor unit a second sensor signal dependent on the at least one process variable, wherein the second sensor signal is generated simultaneously with the first sensor signal;
• transmitting the second sensor signal to the second measuring channel;
• converting the first sensor signal in the first measuring channel into a first digitized sensor signal and transmitting the first digitized sensor signal to the first preprocessing block;
• converting the second sensor signal in the second measuring channel into a second digitized sensor signal simultaneously with the converting of the first sensor signal;
• transmitting the second digitized sensor signal to the second preprocessing block;
• configuring the third preprocessing block identically to the first preprocessing block for a predetermined first time period;
• transmitting the first digitized sensor signal to the verification channel for the first time period and converting the first digitized sensor signal into a digital output signal of the third preprocessing block that is dependent on the first digitized sensor signal;
• synchronizing in a cycle-accurate manner the digital output signal of the third preprocessing block with an output signal of the first preprocessing block and comparing the digital output signal of the third preprocessing block with the output signal of the first preprocessing block in a bit-true manner;
• configuring the third preprocessing block identically to the second preprocessing block for a predetermined second time period;
• transmitting the second digitized sensor signal to the verification channel for the second time period and converting the second digitized sensor signal into a digital output signal of the third preprocessing block that is dependent on the second digitalized sensor signal;
• and
• synchronizing in a cycle-accurate manner the digital output signal of the third preprocessing block with an output signal of the second preprocessing block and comparing the digital output signal of the third preprocessing block with the output signal of the second preprocessing block in a bit-true manner.

An automation technology field device, comprising:

• a sensor unit;
• a control/evaluation unit with a first measuring channel formed by a first preprocessing block, a second measuring channel formed by a second preprocessing block, and a verification channel formed by a configurable third preprocessing block;
• a first A/D converter provided in the first measuring channel and a second A/D converter provided in the second measuring channel, wherein each A/D converter is followed by the respective preprocessing block;
• a switching element via which digital output signals of the A/D converters can be switched to an input of the third preprocessing block;
• and
• a synchronization unit that is configured to control the third preprocessing block such that an output signal of the third preprocessing block and output signals of the first and second preprocessing blocks are synchronized,
• wherein the field device is configured to:
• generate in the sensor unit a first sensor signal dependent on the at least one process variable;
• transmit the first sensor signal to the first measuring channel;
• generate in the sensor unit a second sensor signal dependent on the at least one process variable, wherein the second sensor signal is generated simultaneously with the first sensor signal;
• transmit the second sensor signal to the second measuring channel;
• convert the first sensor signal in the first measuring channel into a first digitized sensor signal and transmitting the first digitized sensor signal to the first preprocessing block;
• convert the second sensor signal in the second measuring channel into a second digitized sensor signal simultaneously with the converting of the first sensor signal;
• transmit the second digitized sensor signal to the second preprocessing block;
• configure the third preprocessing block identically to the first preprocessing block for a predetermined first time period;
• transmit the first digitized sensor signal to the verification channel for the first time period and converting the first digitized sensor signal into a digital output signal of the third preprocessing block that is dependent on the first digitized sensor signal;
• synchronize in a cycle-accurate manner the digital output signal of the third preprocessing block with an output signal of the first preprocessing block and compare the digital output signal of the third preprocessing block with the output signal of the first preprocessing block in a bit-true manner;
• configure the third preprocessing block identically to the second preprocessing block for a predetermined second time period;
• transmit the second digitized sensor signal to the verification channel for the second time period and convert the second digitized sensor signal into a digital output signal of the third preprocessing block that is dependent on the second digitalized sensor signal;
• and
• synchronize in a cycle-accurate manner the digital output signal of the third preprocessing block with an output signal of the second preprocessing block and compare the digital output signal of the third preprocessing block with the output signal of the second preprocessing block in a bit-true manner,
• wherein the control/evaluation unit is configured to determine, by comparing the synchronized output signals of the preprocessing block to be checked and the third preprocessing block whether the preprocessing block being checked is operating correctly.