CTI 2550-A, Installation And Operation Manual

Page: 20 / 43

8 C T I 2550-A Installation and O peration G uide
Figure 11
Underrange Word Value (Bipolar)
NOTE:
This function is new and was not supported in the original 2550 product.
When enabled with JP1 all 8 inputs are scaled for offset mode.
1.9 Using an Input with 20% Offset
Some applications use transducers that provide 1 to 5 volts (4 to 20mA) input signals instead of
0 to 5 volt (0 to 20mA) input signals. You can allow for this 20% offset by including some additional
instructions in your RLL (Relay Ladder Logic) program.
First, subtract 6400 from the input data word (WX). Then, multiply the result by 125 and divide the
product by 100. This yields the following equation:
(WX -6400) x 125 ÷ 100 = 20% offset data word
Consult your PLC programming manual (or program design guide) for information about RLL
instructions used in the conversion.
1.9.1 Using the Module with 20% Offset
If all 8 inputs are used in offset mode the Model 2550-A may be configured to perform the offset
calculation automatically. (See Figure 14 Configuration Jumper Locations). Jumper JP1 when enabled
will configure the module such that all inputs will be scaled for 1-5VDC or 4-20mA operation. No
further relay ladder logic is required for input processing.