Category Archive: Measurements

May
19

Update – Providing 24VDC to Field Devices

3 Wire Terminal Block

In a blog posted late last month I addressed how to provide a 24VDC source of power to a three wire field device. In the past I have used a 24VDC High Side Discrete output to provide  24VDC to these types of devices. This solution can be  implemented in most DCS and PLC systems. If …

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Apr
28

Providing 24VDC to Field Devices

OLYMPUS DIGITAL CAMERA

Some field devices such as an inductive proximity switch may be designed as three wire devices that require a 24VDC source of power. In such cases it is possible to tap into the 24 volt bulk power supply in the rack room and run twisted pair to the device. However, to protect against a short …

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Apr
21

IEC 61987 – List of Properties (LOP)

IEC List of Properties Standard 61987

During the TC65 Plenary meeting each working group gives an activity report that summarizes the status of standards that are being developed or updated. At the Hamburg meeting, March 31- April 4th I was a delegate to the SC65B and SC65C meeting and lead the US delegation in the SC65E meeting. The reports by Peer …

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Apr
14

IEC TC65 Standards Work

IEC Webstore

The international standards for industrial-process measurement, control and automation are developed through IEC TC65. As stated on the IEC web site, the standards developed by TC65 address systems and elements used for industrial-process measurement and control concerning continuous and batch processes. These standards address equipment and systems operating with electrical, pneumatic, hydraulic, mechanical or other …

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Apr
07

TC65 Plenary Meeting

SC65E Meeting Hamburg Germany

Many of the international standards that we depend on in the process industry were created by working groups within IEC TC65: Industrial-process measurement, control and automation. IEC TC65 holds a plenary meeting every two years to review the status of work to develop or update international standards. The most recent plenary meeting was held March …

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Jan
27

WirelessHART – Level Switch

2160 WirelessHART Transmitter

In many tank level control applications, a level switch is installed and used as an interlock to help prevent overfilling the tank. For example, in many existing installations you may find a vibrating fork liquid level switch wired as an input to the control system. However, today it is possible to reduce the cost of installing a …

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Jan
20

WirelessHART – Discrete Measurement

702 Transmitter

Many manufacturers initially introduced WirelessHART field devices that were designed to support continuous process measurements such pressure, flow, temperature, and level. Also, WirelessHART transmitters are now available for analytical measurements such as pH. Recently you may have noticed that some manufacturers have introduced WirelessHART field devices for discrete measurement. For example, Rosemount has released the …

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Oct
14

Control Using Wireless Measurements

Control Using Wireless Measurements

During the initial development of WirelessHart we began researching how to address control applications that use a wireless measurement and/or wireless actuator. To extend battery life a wireless transmitter may be setup to communication the measurement value much slower than the update rate of a wired installation. Also, when the transmitter supports Window communications (as …

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Oct
07

Addressing Control in the Presence of Process and Measurement Noise

Application of Kalman Filter in DeltaV

When a measurement used in a control application is characterized by a significant amount of process or measurement noise then to avoid taking control action on noise filtering may be applied in the transmitter or in the control system. However, when traditional filtering techniques are used it is necessary to increase the PID reset time …

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Feb
25

Identifying Transmitter Problems

Standard PID Parameters

One of the most obvious reasons for poor control utilization is a broken or unreliable transmitter or sensor. As addressed in Chapter 3 of Advanced Control Foundation – Tools, Techniques, and Applications, if the control system is designed to be consistent with the international function block standard, IEC 61804, the status attribute is always communicated …

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