RKI Instruments RI-215A - Manual (Page 17)

RI-215A Operator’s Manual Measuring Mode • 17
Analog Output
The RI-215A’s analog output, available via the yellow and blue wires of the cable
assembly (refer to Figure 3 on page 12), is proportional to the concentration of CO
2
for all
gas ranges (e.g., 0 - 2,000 ppm, 0 - 5,000 ppm, and 0 - 9990 ppm), as shown in Figure 4.
Should the concentration of CO
2
present in the monitoring environment be above full
scale (i.e., it exceeds the upper gas range of your unit), the highest output will be 22 mA,
or 11 V, depending on the output, current, or voltage, selected at the factory. The LCD of
the RI-215A will show a series of brackets (upside down “Us”) between 20 mA
(10 V) and 22 mA (11V). The standard output setting for the RI-215A is 4- 20 mA.
Alarm Point and Ventilation Control
The RI-215A’s alarm relay has a built-in hysteresis of 50 ppm (refer to Figure 6 on
page 18). After the alarm point has been reached (e.g., 1000 ppm), the alarm relay will
activate. As the CO
2
concentration begins to fall, the alarm relay will deactivate 50 ppm
below the activation point (e.g., 950 ppm). The 50 ppm hysteresis keeps the alarm contacts
from “chattering” should the CO
2
concentration hover around the alarm point.
22 mA (11V)
20 mA (10V)
Output
signal
4 mA (0V)
0 ppm Gas
2000 ppm
5000 ppm
9990 ppm
Figure 5: Model RI-215A’s CO
2
Level to Output Signal
Concentration
Maximum
Output