Yokogawa HIMHART Manual de usuario descargar pdf (Pagina 16)

HIM

16 The Interface Solution Experts

Smart HART



Loop

Interface and Monitor

Analog Outputs Parameters

The HIM comes with either two (–2AO) or three (–3AO)

analog outputs. The

Analog Outputs

tab allows you to

specify which HART variable is to be monitored as the

source of the analog output, the input range and output

range, and how the output will react when the variable

input is out of range. To program the Analog Outputs

parameters, change the settings in the

Output1/2/3

boxes, then press

Quick Set

. See the descriptions

below of the various sections of the screen.

Source

defines the variable that the analog output will

monitor. Notice that selecting one of the scaled

outputs will require you to make changes to the

Scaling

tab, and selecting the Custom Curve option will

require you to make changes to the

Custom Curve

tab.

Input/Output Range

The

Input

Output Range

defines the range of the

source input and the range of the analog output.

These two sets of fields can be used to scale the

HIM’s output.

Figure 12. Analog Outputs Tab

For example, you have a vortex flow meter with an

imbedded RTD that measures the process

temperature, and that temperature is assigned to the

HART Secondary Variable. The full range of the RTD

sensor is from –400°F to +1760°F, but your flow

stream will always be between 0° and 400°F. To scale

the analog output, for Output 1, set the

Source

as SV.

Set the

Input Range

to 0° and 400°F, and the

Output

Range

to 4mA to 20mA. Click

Quick Set

to download

the new configuration file to the HIM.

Output Current Box

The

Output Current

Box on the

Analog Outputs

Tab

displays up-to-the-second information on the value, in

mA, of the analog output.

Fail Mode

The

Fail Mode

setting determines how the HIM will

respond when its monitored input fails. If

Fail Mode

set to

High

and the measured input goes out of range,

or any detected error occurs in the HART transmitter,

the analog output will output a 23.6mA signal. If Fail

Mode is set to

Low

and the measured input goes out of

range, or any detected error occurs in the HART

transmitter, the analog output will output a signal that

is 90% of the lower range value below 4mA; it will

output 0mA if the lower range is set to 0mA.

Fail Mode

is set to

Hold Last

, the HIM will continue

to output the last value it recorded before the input

failed. If

Fail Mode

is set to

Hold Last Then High

Hold Last Then Low

, the HIM will continue to output the

last value recorded for a set amount of time (according

to Hold Last Duration box), then either fail high or fail

low, respectively.

Quick Set Button

The

Quick Set

button causes the software to configure

the instrument’s analog output settings to match those

currently entered in the PC Software.

Trim Button

The

Trim

button brings up the Trim Menu, allowing you

to set the device’s output to match the reading of the

loop. Refer to the

Programming the Trimming

Parameters

section of this manual for more

information.

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Yokogawa HIMHART Manual de usuario Pagina 16

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