Campbell CVF4 Especificações descarregar pdf (Página 53)

Appendix B. CNF4 Heater/Ventilator

'CNR4 thermistor measurement

BrHalf (Vs_Vx,1,mv5000,16,Vx1,1,2500,True ,0,250,1.0,0)

Rs = 1000*(Vs_Vx/(1-Vs_Vx))

cnr4_T_C = 1/(1.0295e-3+2.391e-4*LN(Rs)+1.568e-7*(LN(Rs))^3)-273.15

'Convert CNR4 temperature to Kelvin

cnr4_T_K = cnr4_T_C+273.15

'Correct the long-wave radiation values from pyrgeometers

long_up_corr = long_up+5.67e-8*cnr4_T_K^4

long_dn_corr = long_dn+5.67e-8*cnr4_T_K^4

'Compute short-wave net radiation

Rs_net = short_up - short_dn

'Compute long-wave net radiation

Rl_net = long_up - long_dn

'Compute albedo

albedo = short_dn/short_up

'Compute net radiation

Rn = Rs_net + Rl_net

'CNF4 ventilator control - the ventilator will be turned on when flag(1) is set high

SW12 (1,flag(1))

'CNF4 heater control - the heater will be turned on when flag(2) is set high

SW12 (2,flag(2))

CallTable cnr4_data

CallTable cnr4_ts

NextScan

EndProg

B.5 CNF4 Heater/Ventilator Maintenance

B.5.1 Testing the Heater

The optional CNF4 consists of a heater and a ventilator. To check the heater

unit, measure the resistance between the two heater wires (green and yellow).

The resistance value of the heating resistor inside should be around 15 Ω (cable

resistance should add about 0.026 Ω per each foot of cable). An infinite

resistance reading indicates the likelihood of a broken wire, or cable.

B.5.2 Testing the Ventilator

To check the ventilator, first measure the impedance of the ventilator motor.

The value should be around 30 Ω (cable resistance should add about 0.026 Ω

per each foot of cable). If the correct resistance value is measured, but the

ventilator still mal-functions, it is possible that the ventilator is stalled by an

object blocking the fan. Remove the black cover at the bottom side of the

ventilator unit, by prying it open with a small flat-head screw driver or by

B-11

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Campbell CVF4 Especificações Página 53