Moore Industries RIY - Page 15

RIY
The Interface Solution Experts 13
Example 2:
• For zero-percent differential input
• R10 Range (Input Code)
• Pt 100 Ω 385 RTD
• –50 °C differential
Input #1 (box #1): -50 °C (80.30 Ω )
Input #2 (box #2): 0 °C (100.00 Ω )
Differential: -50 °C
Selecting a 100-percent Differential Input. The
following examples show how to determine a 100-
percent differential input setting that produces a 100-
percent (full-scale) output.
Example 1:
• For 100-percent differential input
• R10 Range (Input Code)
• Pt 100 Ω 385 RTD’s
• 100 °C differential
Input #1 (box #1): 100 °C (138.50 Ω )
Input #2 (box #2): 0 °C (100.00 Ω )
Differential: 100 °C
Example 2:
• For 100-percent differential input
• R10 Range (Input Code)
• Pt 100 Ω 385 RTD’s
• 50 °C differential
Input #1 (box #1): 50 °C (119.39 Ω )
Input #2 (box #2): 0 °C (100.00 Ω )
Differential: 50 °C
Figure 6 illustrates the hookup required to range a
unit for a differential input. Notice that an additional
decade resistance box is required over the standard
ranging procedure. Refer to the Standard Ranging
Subsection earlier in this section for information
regarding zero and span settings and trimming.
Ranging the RIY for a Differential Input
Some applications require a differential input, which
consists of two sensors connected to the RIY where
the difference between them influences the 4-20 mA
output of the RIY. For example, when resistance of
one sensor (RTD) increases while the other remains
constant the output of the RIY may also increase
toward 20 mA. If both inputs are varying, increasing
and decreasing in value, the output will vary propor-
tionally with the difference of the two inputs.
Although the RIY may be quick ranged for differential
inputs , the following procedure allows you to verify
the response of the RIY as you vary the inputs.
To range an RIY for differential input operation, you
must determine the minimum and maximum differen-
tial input values for the intended application. The
lower differential value will be used to set the zero
output level and the higher differential value will be
used to set the span output level. The following
examples show how to determine the zero-percent
and full-scale differential values based on known
(substitute your own values) minimum and maximum
input temperature ranges.
Selecting a Zero-percent Differential Input. The
following examples show how to determine a zero-
percent differential input that produces a zero-percent
output. The RIY responds to negative (–), zero-
percent differential input values, as determined in
example 2.
Example 1:
• For zero-percent differential input
• R10 Range (Input Code)
• Pt 100 Ω 385 RTD
• 0 °C differential
Input #1 (box #1): 0 °C (100.00 Ω )
Input #2 (box #2): 0 °C (100.00 Ω )
Differential: 0 °C