Baker Hughes Masoneilan SVI II AP, Быстрый старт

Страница: 103 / 108

Masoneilan SVI II AP Digital Positioner Quick Start Guide = | 103
© 2018 Baker Hughes, a GE company, LLC. All rights reserved.
This discussion explains how to determine compliance voltage for an SVI positioner. It applies to
the SVI II AP, SVI II ESD, SVI II APN and SVi1000.
A definition of compliance voltage is: The voltage that must be available at the control system
output in order to drive the control current through the SVI II AP and all the resistive devices in
series with it.
Measuring the voltage across the SVI II AP terminals doesn't give the true available system com-
pliance voltage as the positioner self-regulates voltage as current flows through it. Additionally,
it also doesn't confirm what system voltage is available under load conditions.
Therefore, if com-
pliance testing needs to be done, it is best done before installation.
Use a 1K potentiometer as this is the maximum for most analog output cards and as at 20 mA
this equals 20 VDC, which is a sufficient maximum.
Compliance Test Set-Up
1. Configure a test set-up as in Figure 38.
Figure 38 Compliance Voltage Test Set-Up
2. Send 4 mA to the test set-up.
3. Increase the potentiometer value until the loop current reaches 3.95 mA.
4. Read the voltage across the potentiometer, which should be > 11 VDC. This is the
available system voltage at the minimum output.
D. Determining an SVI Positioner
Compliance Voltage in a Control System