where
RH
cabinet
= RH value at a given point inside the cabinet (%).
T
cabinet
= Temperature at the point where we want to determine the RH (˚C).
RH
board
= RH value read from the onboard RH sensor (%).
T
board
= Temperature read from the onboard RH sensor (˚C).
The RH sensor type is HDC1080 (Texas Instruments). It communicates with the GPIC through
an I
2
C bus connected to the LVTTL lines. The following table shows the signal assignments
for the RH sensor. Consult the Texas Instruments Web site for a full description of the RH
sensor communication protocol.
Table 41. RH Sensor I
2
C Lines
I
2
C Signal LVTTL Line
SCL DIO26
SDA DIO27
Relay Connector
The sbRIO-9687 provides connections for four relay control outputs. Each output has a relay
control DO+ and a current return pin, relay control DO-. The sbRIO-9683 and sbRIO-9684
have current sinking outputs, which means that the relay control DO+ is driven to relay control
DO- when the channel is ON.
The following table provides pinout information for the relay connector.
Table 42. J4 Relay Connector Pinout
Pin Signal Pin Signal
1 +24 V 7 +24 V
2 DO0– 8 DO0+
3 DO1– 9 DO1+
4 DO2– 10 DO2+
5 DO3– 11 DO3+
6 GND 12 GND
The relay control lines are directly connected to the GPIC relay control connector. For further
details regarding best practices for relay connections, refer to the NI 9683 User Manual and
Specifications and the NI 9684 User Manual and Specifications.
sbRIO-9687 User Manual | © National Instruments | 47
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