Installing the CNF4 Heater/Ventilation Unit in Biomet Systems

The CNF4 Heating and Ventilation Unit (part number 7900-145) is used to prevent condensation or frost buildup on the Kipp & Zonen CNR4 pyrgeometer windows and pyranometer domes. Condensation on the pyrgeometer windows will absorb far-infrared radiation and lead to measurement errors. These can be avoided by using the CNF4. See the manufacturer’s documentation for more information. Here we describe how to use the CNF4 in LI-COR biomet data acquisition systems. Read the manufacturer's instructions before using the CNF4.

Note: Due to heat dissipation from the CNF4, measurements of sensor temperature may be less accurate. However, the improvements in accuracy that result from heating will be larger than errors that result from heating.

Components

The CNF4 kit includes the heater/ventilator, three pan-head machine screws with washers, four flat-head screws, the protective shroud, and the CNF4 power cable. Cables are available in 10, 25, and 50 meter lengths.

The CNF4 kit includes two relays to control the power supply (part number 290-14669) and a pack of wire leads. It includes four 11-cm 18-gauge red wires, two 30-cm 20-gauge blue wires, and one 11-cm 18-gauge black wire (not used). The relays and wire leads are required for Sensor Package 4 only.

Assembling the CNF4

After attaching the temperature and sensor cables to the radiometer, attach the heater/ventilator to the CNR4 body using the three machine screws. Route the cables around the fan in the ventilator. Attach the protective shroud with the remaining four screws. Connect the ventilator power cable to the unit.

Installing the CNF4 control components

Different sensor packages have different wiring.

For Sensor the Premium Package and Package 2

If you have two DAqMs, the CNF4 wires connect to the DAqM. The CNF4 is controlled by the DAqM's switched power supplies. The green and gray wires for the tachometer are not used.

Table 1‑1. CNF4 connections.

CNF4 Wire	Color	Connection
Ventilator (+)	Yellow	SW2
Ventilator (-)	Brown	GND (SW2)
Tacho (+)	Green	Not used
Tacho (-)	Gray	Not used
Heater (+)	Black	SW1
Heater (+)	White	SW1
Heater (-)	Red	GND (SW1)
Heater (-)	Blue	GND (SW1)
Shield (black)	Black	GND (SW2)

For Package 4 and custom packages

For Sensor Package 4, you'll need to install two relays and wire leads, which are required to actuate the relays and provide the timer-controlled power to the CNF4. The CNF4 wires connect to the relays and DIN terminals. The green and gray wires for the tachometer are not used.

Description	Color	Terminals Connected
Ventilator Relay Control	Blue	C4 to Left Relay 4/A2
Ventilator Relay Power	Red	13 to Left Relay +3/A1
Ventilator Power	Red	13 to Left Relay +1/L1
Heater Relay Control	Blue	C3 to Right Relay 4/A2
Heater Relay Power	Red	14 to Right Relay +3/A1
Heater Power	Red	14 to Right Relay +1/L1

Table 1‑2. CNF4 connections for Sensor Package 4.

CNF4 Wire	Color	Connection
Ventilator (+)	Yellow	Left Relay 2/T1
Ventilator (-)	Brown	Blue DIN Terminal 11
Tacho (+)	Green	Not used
Tacho (-)	Gray	Not used
Heater (+)	Black	Right Relay 2/T1
Heater (+)	White	Right Relay 2/T1
Heater (-)	Red	Blue DIN Terminal 11
Heater (-)	Blue	Blue DIN Terminal 12
Shield (black)	Black	Blue DIN Terminal 12

Configuring the timer controls

The required blocks are already included in programs that support the CNF4. The heater and ventilator are controlled by separate relays (and separate blocks) so they can be configured independently. Typically the heater should be on 1 hour before sunset to 1 hour after sunrise. Read the manufacturer's recommendations for more information.

In the Blueprint Utility, configure the timing parameters. Expand the Kipp & Zonen CNF4 block and set the Turn On time and duration for both the heater and the ventilation unit.