Siemens SITRANS P Instruções de Operação descarregar pdf (Página 133)

7.21.5 Limit modules

Introduction

The diagnostic functions of this device give you an option to monitor the measured values in

programmable

limits. If the limits are not adhered to, the device sends a warning through HART

communication or notifies a higher-level instance about an analog fault current.

Monitoring of current saturation

You can monitor the current output in the saturation range using a simple limit module. This

limit module is configured and activated via HART communication. For HART communication,

use a HART communicator or PC software such as SIMATIC PDM.

You need to set two time periods to configure the limit module:

The first time period specifies how long the current output is allowed to be in saturation before

an interrupt is triggered and the device outputs its set fault current. This first time period is the

response time.

The second time period specifies the duration of the interrupt. This second time period is the

stop time.

Different outputs of the fault current corresponding to the set response and stop times are

shown in the following example.

Configuring the direction of fault current

The current value is proportional to pressure within the saturation limits. When the saturation

limits are exceeded, the direction of fault current can however vary from the direction of

saturation. The upper or the lower fault current is displayed depending on the parameter

settings of the direction of fault current.

You can configure the direction of fault current for a current saturation interrupt depending on

your requirements. The following settings are possible under the current saturation menu:

Active interrupt value The applicable settings are those under the current interrupt type

menu command.

Inverse interrupt value The applicable settings are the inverse settings under the current

interrupt type menu command.

Saturated interrupt value The fault current is output in the direction of current saturation.

Inverse saturated interrupt

value

The fault current is output in the opposite direction to current

saturation.

The

difference between different settings is evident in examples 3 and 4 in the following figure.

Example 3 shows the direction of fault current with the "Saturated current value" setting.

Example 4 shows the direction of fault current with the "Active upper interrupt value" setting.

Example

The configured saturation limits in the following figures are 3.8 mA and 20.5 mA.

Operating functions through HART

7.21 Diagnostic functions

SITRANS P, DS III series with HART

Operating Instructions, 09/2012, A5E00047092-08 131

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