Chapter 1. Description; Asynchronous Operation; Compatibility With Immediate I/O; 100 Ohm Or 120 Ohm Rtds - Control Technology CTI 2552-A Installation And Operation Manual

CHAPTER 1. DESCRIPTION

The 2552-A Eight Channel RTD Input Module is a member of Control Technology's family of I/O
modules compatible with the SIMATIC® 505 series programmable controllers. The Model 2552-A
is designed to translate 100 Ohm platinum RTDs, 120 Ohm nickel RTDs or millivolt input signals
into equivalent digital words which are then sent to the programmable controller (PLC).
The 2552-A RTD Input Module features built-in independent two, three, or four lead compensation
for each RTD input. Support for other RTD types is available through special request from the
factory. Call CTI at 1-800-537-8398 to determine if support is available for your special RTD type.

1.1 Asynchronous Operation

The module operates asynchronously with respect to the PLC; a scan of the PLC and input sampling
of the module do not occur at the same time. Instead, the module will translate all inputs in one
module update (15 milliseconds maximum) and store the translated words in a buffer memory. The
PLC retrieves the stored words from the module buffer memory at the start of the I/O scan.

1.1.1 Compatibility with Immediate I/O

The Model 2552-A has been tested and is compatible with the Immediate read function of the
SIMATIC® 545 and 555 PLC.

1.2 100 Ohm or 120 Ohm RTDs

Each of the module's eight channels may be configured to receive either a 100 Ohm platinum RTD or
a 120 Ohm nickel RTD input signal (two, three or four wire) or a DC voltage signal ranging from 0 to
100 millivolts. Selection of 100 Ohm or 120 Ohm RTDs or millivolts are made via internal switch
and jumper settings (see sections 2.4.1 and 2.4.5).
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CTI 2552-A Installation and Operation Guide