Basic Operation; Position Definition; Figure 1: Principles Of Operation Of Logix 505 - Flowserve Logix 505+ User Instructions

Logix 505+ positioner repair is limited to the replacement of sub-as-
semblies and circuit boards with Flowserve-manufactured replace-
ments as outlined in this manual.
c
DANGER: Substitution of with non-factory positioner components
may impair intrinsic safety.
a
CAUTION: Before products are returned to Flowserve for repair
or service, Flowserve must be provided with a certificate which
confirms that the product has been decontaminated and is clean.
Flowserve will not accept deliveries if a certificate has not been
provided (a form can be obtained from Flowserve).
Apart from the operating instructions and the obligatory accident
prevention directives valid in the country of use, all recognized regula-
tions for safety and good engineering practices must be followed.
Logix 505+ Digital Positioners FCD LGENIM0109-03-A4 – 09/15
®
Principles Of Operation

1.8 Basic Operation

The Logix 505+ digital positioner is a two-wire 4-20 mA input digital
valve positioner. The positioner is completely powered by the 4-20
mA input signal. Start-up current must be at least 3.8 mA. The Logix
505+ positioner can control both double- and single-acting pneumatic
actuators with linear or rotary mountings.
The Logix 505+ digital positioner is an electronic and pneumatic
closed-loop feedback instrument. Figure 1 shows a schematic of a
Logix 505+ positioner installed on a single-acting linear actuator for
air-to-open action. Figure 2 shows the double acting option.

1.9 Position Definition

Whether in Analog or Digital Source, The position at 0% is always
defined as the valve in a closed position and 100% is always defined
as the valve in an open position. In Analog Source, the 4-20 mA signal
is converted to a position (in percent). During loop calibration, the
signals corresponding to 0% and 100% are defined.

Figure 1: Principles of Operation of Logix 505+

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