Method for operating a field device and corresponding field device

Patent metadata

Field	Value
Publication number	US-10044348-B2
Application number	US-201615086301-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Apr 1, 2015
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

A method for operating a field device, and a field device that is operated according to the method, in which a measured value is generated, the measured value being assigned a current set point, a target current signal being issued depending on the current set point, wherein an actual current signal is fed back and the target current signal is compared to the actual current signal. To provide more exact comparison of signals a cross-correlation of the target current signal with the actual current signal is formed for comparison.

First claim

What is claimed is:

1. A method for operating a field device, comprising:
generating a measured value,
assigning electrical current set point to the measured value,
issuing a target electrical current signal depending on the electrical current set point, and
feeding back an actual electrical current signal and comparing the target electrical current signal to the actual electrical current signal,
wherein a cross-correlation of a digital version of the target electrical current signal with a digital version of the actual electrical current signal is formed for the comparison to compensate for time lags between the target electrical current signal and the actual electrical current signal caused by respective filtering and/or conversions of the actual electrical current signal in the target electrical current signal, and
wherein, when the target electrical current signal is found to deviate from the actual electrical current signal by an amount above a set level, an alarm signal is issued that prompts a user to react for carrying out repairs or exchange of the field device.

2. The method according to claim 1 , wherein an auto-correlation of one of the target current signal and of the actual current signal is formed, and wherein a deviation of the correlated signals is calculated in that the values of the cross-correlation of the actual current signal with the target current signal are related to the value of the auto-correlation of said one of the current set point and of the auto-correlation of the actual current signal.

3. The method according to claim 1 , wherein the target current signal is digitized with a first sampling rate and the actual current signal is digitized with a second sampling rate that is set at a fixed relation to the first sampling rate.

4. A field device, comprising:
at least one signal outlet and
at least one control component which generates a measured value and assigns a current set point to the measured value, generates a target current signal depending on the current set point and issues the target current signal via the signal outlet and wherein the control component imports an actual current signal and compares a digital version of the target current signal to a digital version of the actual current signal, the control component forming a cross-correlation of the target current signal with the actual current signal for comparison to compensate for time lags between the target current signal and the actual current signal caused by respective filtering and/or conversions of the actual current signal and the target current signal, and
wherein, in response to the target electrical current signal being found to deviate from the actual electrical current signal by an amount above a set level, said at least one control component is adapted to cause an alarm signal to be issued that prompts a user to react for carrying out repairs or exchange of the field device.

5. The field device according to claim 4 , wherein a converting device is provided for conversion of digital signals to analog signals.

6. The field device according to claim 5 , wherein an analog filter is connected behind the converting device.

7. The field device according to claim 6 , wherein the analog filter is a low pass filter having a cutoff frequency less than or equal to 25 Hz.

8. The field device according to claim 5 , wherein a digital filter is provided for filtering the target current signal.

9. The field device according to claim 4 , wherein an analog-digital converter is provided that digitizes the imported actual current signal.

10. The field device according to claim 4 , wherein the field device is temperature measuring device with a temperature sensor.

11. The method of claim 1 , where a temperature measuring device with a temperature sensor is used for generating said measured value.

Assignees

• Krohne Messtechnik Gmbh

Inventors

• Kunze Johannes

Classifications

• H03K5/24 Primary

  the characteristic being amplitude · CPC title

• G05B19/0423

  Input/output · CPC title

• G05B23/024

  Quantitative history assessment, e.g. mathematical relationships between available data; Functions therefor; Principal component analysis [PCA]; Partial least square [PLS]; Statistical classifiers, e.g. Bayesian networks, linear regression or correlation analysis; Neural networks · CPC title

• G01D3/032 Primary

  affecting incoming signal, e.g. by averaging; gating undesired signals · CPC title

• G08C19/02

  in which the signal transmitted is magnitude of current or voltage (G08C19/36, G08C19/38 take precedence) · CPC title